I n r e r ~ t h n aPsychogeriairics, l Vol. 4, Suppl. 2,1992 0 1992 Springer Publishing Company
Toward an Understanding of Cognitive Functioning in Geriatric Depression Leonard W. Poon ABSTRACT. This paper addresses the questions of whether depression compromises cognition in the elderly and whether discernable patterns of cognitive performances could be differentiated between patients with severe depression and those with organic dementia. Published data on geriatric depression and cognitive functioning are divided in demonstrating a depression effect. Further examinationand external validation by new data show that the depression effect on discrete cognitive tasks is (1) small, and (2) sensitive to the confounding of sampling and task variables. Future research must take these factors into account. Patterns of cognitivefunctioning in depression and dementia are different and can be differentiated using a variety of measures. This review finds the term pseudodementiainappropriateand misleading and recommends that it be abandoned.
The purpose of this paper is to address two frequently asked questions about geriatric depression. One, does depression compromise cognitive functioning in older individuals? Two, are there discernable patterns of cognitive performances that differentiatepatients with severedepression from those with organic dementia? Answers to these two questions carry implications for clinical, research, and theoretical domains. From an empirical research perspective, data from published literature can be divided into two camps -those that demonstrated a depression effect on cognition and those that did not. This paper will review a sample of published data from both camps and attempt to isolate relevant factors that could contribute to the disparate findings. When viewed from a clinical diagnostic perspective, depression is assessed on a routine basis when evaluating organic brain disorders.The reason is that depression in the elderly could produce sufficient cognitive impairment - a “pseudodementia” (Kiloh, 1961) - that could be misdiagnosed as an organic dementia. This paper will review quantitative data based on discrete cognitive performances as well as cognitive profiles, combining several cognitive tasks to see ifcognitive performancesin depression and dementia are discernable. Finally, based on the evidence reviewed, this paper will summarize From the Gerontology Center, University of Georgia, Athens, Georgia, U.S.A. (L. W. Poon, PhD)
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the necessary and sufficient conditions that must be present for depression to influence cognition in elderly individuals.
CLINICAL SYNDROME OF DEPRESSION Clinical depression refers to a cluster of symptoms in which the primary characteristic is dysphoria, a feeling of being sad, downhearted, or blue. The American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM-111; APA, 1980) and the Research Diagnostic Criteria (RDC; Spitzer et al., 1978) identified the following three key features in depression. One, a duration of at least two weeks must be established for both mood and symptomatic disturbances. Two, the primary feeling state during the episode must be identified. Three, at least four (DSM-111) to five (RDC) of the following symptoms must be present nearly every day of the episode in question if the patient is to be diagnosed with major depression. Two of the following symptoms must be present in order to be diagnosed with minor depression. Poor appetite or significant weight loss, or increased appetite or significant weight gain Insomnia or hypersomnia Psychomotor agitation or retardation Anhedonia Loss of energy, fatiguability, or tiredness Feelings of self-reproach and excessive or inappropriate guilt Complaints or evidence of diminished ability to think or concentrate Recurrent thoughts of death or suicide, wishes to be dead, or evidence of suicidal behavior Evidence of functional impairment, or taking medication, or seeking help for the disorder. For the classification of different subtypes of depression see DSM-I11 (APA, 1980, pp. 218-223).
THE EFFECTS OF DEPRESSION ON COGNITIVE PERFORMANCES Prior to reviewing the effects of depression on cognitive performances of elderly adults, it should be noted that depression has been found to correlate strongly with frequency of memory complaints (e.g., Kahn et al., 1975; Popkin et al., 1982; Zarit et al., 1981), but neither depression nor complaint has been related to the level of memory performances. This has led some investigators to postulate that depressed patients are poor evaluators of their own clinical symptoms. The relationship among depression, self-assessment, and cognitive performance is an important clinical and research area. However, this area will not be reviewed in this paper.
Cognitive Functioning in Geriatric Depression
243
Presumably, clinical symptoms identified in depression would predict adverse effects on attention, concentration, motivation, learning, memory, and decisionmaking performances. However, empirical evidence presented in the literature is far from supportive of this prediction.
Supportive Evidence Salzman and Gutfreund (1986) provided a concise summary of effects of depression on cognition that is worth repeating here. Decreased acquisition and recall of new information (Breslow et al., 1981; Cohenet al., 1982; Davis & Unruh, 1980;Friedman, 1964; Henry et al., 1973; Jarvik et al., 1972); increased emrsof omission (Henry et al., 1973;Jarviket al., 1972;McAllister, 1981; Whitehead, 1973); transposition errors, mispairing, and reversal of stimulus-response words (Henry et al., 1973; Whitehead, 1973); decreased ability to impose organization on unorganized information (Breslow et al., 1981; Weingartner et al., 1981, 1982); less effective coding and memory strategies (level of processing) (Breslow et al., 1981; Weingartner et al., 1981, 1982); fluctuating deficits in episodic memory; increased access to sad memories (Bower, 1981; Fogarty & Hemsley, 1983; Isenet al., 1978; Natale & Hantas, 1982; Teasdale & Fogarty, 1979)and, with increasing depression, decreased access to pleasant memories (Breslow et al., 1981); altered guessing strategies; taking fewer risks in a task (Miller & Lewis, 1977), reluctanceto give oneself the benefit of the doubt (Alloy & Abramson, 1979),or reluctance to use negative feedback as a basis for change in strategy (Silberman et al., 1983); and decreased attention and reaction time (Breslow et al., 1981; Cohen et al., 1982; Glass et al., 1981). The large number of studies that showed the detrimental effects of depression on cognition led Weingartner (1986) to conclude that every conceivable stage or type of information-processing system has been implicated in determining aspects of cognitive dysfunction in depression.
Nonsupportive Evidence Given that there are ample data that could differentiate the cognitive performances of depressed elderly from controls, one could postulate that psychiatrists and psychologists who work regularly withdepressivescould easily identify depressives from controls based on cognitive performances. On the contrary, the results are not as straightforward as one would postulate. The not-so-straightforward data came from a large National Institute of Mental Health (NIMH) multihospital collaborative study conceived in the 1960s of drug
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treatment in depression (Raskin et al., 1982). A state-of-the-art battery of psychomotor, learning, and perceptual tests was used. The collaborative study sample employed 277 inpatients (17 to 70 years) and 112 normal controls who matched them in age, sex, and education. Thirty-two patients with adiagnosis of progressive idiopathic dementia, senile onset, were included for some of the comparisons. At the time the collaborative study was conceived, one of the investigators had just published a paper that showed either no deficits or small cognitive, perceptual, and psychomotor deficits in 55 severely depressed patients, compared with a matched sample of 65 controls (Friedman, 1964). Fortunately orunfortunately, the outcome of the NIMH collaborative study showed there were significant cognitive differences between depressives and controls. However, the magnitudes of difference between depressed and controls were found to be influenced by the age of the subject, the severity of depression, and the level of education and intelligence. In this instance, the same investigator (Friedman) who had conducted the state-of-theart studies in one of the foremost research centers in the world found opposite results. How could this be? The NIMH investigators (Raskin, 1986) offered a possible explanation that the earlier Friedman (1964) patient samples were above average in verbal abilities, as reflected in their WAIS vocabulary subtest scores, in comparison to the collaborative study samples. Higher IQ tends to moderate the effects of aging and depression on cognitive tests. In this example, we have seen that sample characteristics can profoundly influence the outcome of a study on depression. The concomitant effects of intelligence and education levels within and between comparison samples could under- or overestimate group differences (Poon et al., 1984). Depression is complex, and future research needs to develop a better understanding of the phenomenon as well as methodologies to study it. The NIMH collaborative study also provided data regarding the ease of differentiating depressed from normal subjects.Table 1(from Raskin, 1986)summarizes the ratings of eight items from the Global Assessment of Psychopathology scale. The items represented symptoms that are present in depression. The ratings were conducted by psychiatrists and psychologists on demented and nondemented subjects who were either depressed or nondepressed. Significant discriminations (indicated by significant F ratios) in the ratings of the four samples were obtained. However, examination of the post-hoc analyses showed that the discrimination was obtained between demented and nondemented samples, and not between the depressed and nondepressed samples! The lesson to learn from this data set is that discrimination of depressive signs is not easy, even when undertaken by professionals. Following the conflicting results of the NIMH studies, the literature contains a significant number of studies that showed no cognitive impairments in depressed subjects (e.g., Camp & Niederehe, 1978; Derry & Kuiper, 1981; Golub, 1975; Granick, 1963; Kahn et al., 1975; Kendrick & Post, 1967; Miller & Lewis, 1977; Niederehe, 1986; Niederehe & Camp, 1985; Orme, 1957; Perlin & Butler, 1963; Popkin et al., 1982; Roth & Rehm, 1980).
Cognitive Functioning in Geriatric Depression
245
TABLE 1. Mean Scores Showing Significant Differences Among Groups on Selected Symptoms Rated by Psychiatrists and Psychologists (Geriatric Test Battery File) (Adapted from Raskin, 1986) Demented
Variable Appears confused, perplexed’ Seems disoriented’ Appears inattentive’ Appears forgetful2 Appears depressed, blue’ Appears tense, anxious2 Severity of illness3 Severity of mental deterioration4
Nondemented
(1) (2) (3) (4) Depressed Nondepressed Depressed Normal Subjects ( n = 13) (n = 19) ( n = 24) ( n = 150)
F
Difference
2.46
2.16
1.17
1.12
54.78*
1,2-3,4
2.23 1.23 2.62 3.38 2.23 3.00 2.23
2.16
1.12 1 .oo 1.88 3.54 2.62 2.33 1.67
1.03 1.03 1.19 1.17 1.17 1.11 1.10
57.96** 4.02**
1,2-3,4 1-4,2,3 1 ,2-3-4 3,1-24 3,1-2-4 1-2,34 2.1-3-4
1 .oo
2.42 I .89 1.57 2.47 2.37
51.51**
241.77** 64.41** 108.60** 93.98**
’Groups are listed in order of decreasing scores. A comma indicates no significant difference between scores; a hyphen indicates a significant difference. ’Rated on a 5-point scale from Not at all to Extremely. ‘Rated on a 7-point scale from Normal, not ill at all to Among the most extremely ill patients. “Rated on a 5-point scale from Normnl. shows no signs of deterioration to Among the most deteriorafedpatients. * p < .05, two-tailed. **p < .01, two-tailed.
Summary The literature shows a stalemate on the question of whether depression exerts an adverse effect on the cognitive functions of the elderly. The number of opposing findings make it necessary to examine more intensely our understanding of the mechanisms of depression and their effects on cognitive functioning.
AN ATTEMPT TO MAKE SENSE OF CONFLICTING RESULTS In attempting to understand factors that could possibly contribute to the conflicting results in the literature, Tables 2 to 5 outline four clusters of studies detailing the subject characteristics, cognitive tasks, and magnitudes of depression effects from 12 studies of geriatric depression and cognition. Most of the studies were published between 1985 and 1990. Three general observations are made from examining the 12 studies. First, the studies employ different cognitive tasks that made comparisons across studies difficult. Second, some studies made certain there was no confoundingof dementia and some did not. The possibility that dementia could be superimposed on the depressed and control groups could further confound the conclusions about depression effects. Third, some studies controlled for education and IQ and some did not. These concomitant measures were found to be important in the NIMH collaborative study (Raskind, 1986).
=
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Ham-D
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10 major depressive inpatients
La Rue et a]., 1986
Age = 73.4 +-10.1
= 71.0
2 Age
20 normal community residents
Control (C)
20 depressed assessed by psychiatrist No tests listed X Age = 69.0
Exper (D)
Subjects
Gibson, A. J. 1981
Authors
IQ-NO
MSG GAS WAIS Age-Yes Ed.-Yes
Dementia-Yes
IQ-NO
No tests listed Age-Yes Ed. -No
Dementia-Yes
Dementia AssessediMatched Age, Ed, IQ? Tasks
Fuld ObjectMemory Evaluation
Inglis PairedAssociate Learning Test
Benton Visual Retention Test
Immediate free recall of words from Miller (1971) (verbal) Object Learning Test of Revised Kendrick Ballery (Visual)
TABLE 2. Depression Effect
Control
OME Retrieval D: 6.8 C: 9.2 Consistent Retrieval D: 5.3 C: 8.6 Category Retrieval D: 37.0 C: 52.4
PALT Total Correct Responses D: 13.5 C: 14.1 Total Correct Responses D: 6.1 C:10.5
VRT Total Correct D: 3.1 C5.5 Total Errors D: 13.5 C: 7.0 Error TypeOmissions D: 4.0 C: 1.2
Visual Total Recall D: 26.9 C: 38.3
Verbal Total Recall D: 25.7 C: 34.7
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.71*
.61*
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.58
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.56*
.70*
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1989
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IQ-NO
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Ed-No IQ-No
Age-Yes
WMS >80: No dementia
Dementia-Yes
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Symbol
WAIS Digit
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8.0 10.9
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9.0 8.2
8.5
7.2
4.0
7.3
6.6
4.4
13.6
C:
52 53 56 55 33
78 81 71 71 67
Memory Scanning Intercept for Mean Reaction Time (MS) D: 870.0 C: 685.0
WAIS Digit Symbol Measured in Seconds D: 306.4 C: 184.2
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60’s
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30’s 40’s
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Table 2 presents four studies that support the detrimental effects of depression. That is, the performances of the depressed were clearly lower than control (ratio D/ C in the table). For example, the Gibson (1981) study is an unequivocal demonstration of a depression effect on a verbal and a visual task. The age range of the depressed and control groups was matched, and dementia was evaluated to rule out possible confounding. The results show that depressed subjects performed significantly poorer, at about 70% of the performance level of the controls. Similar outcomes are found in the LaRue et al. (1986) study. Although significant depression effects were found in the Benton Visual Retention and the Fuld ObjectMemory tests, a depression effect was not found in the Inglis Paired-Associate Learning test. This is also true in the Sweeney et al. (1989) study where adepression effect was found in the Famous Faces test, but not in the Rey Auditory Verbal Learning test. Although dementia screening was not noted in the Hart and Kwentus (1987) paper, clear group differences were obtained. Since no dementia assessment was made in this study, one should be cautious in interpreting the results, however. Dementia could be present with the depression group that could increase the magnitude of group difference. Table 3 outlines a study by Weingartner et al. (1977) that demonstrates the importance of task selection in the study of depression. Weingartner (1986) postulated that patterns of depression deficit seen in the literature could be a function of the amount of effort demanded from the subject. This effortful dimension is usually not controlled in studies of depression. Depression effect would be more evident in effort-demanding tasks and not obvious in superficial processing and automatic tasks. This postulation is supported by the data shown in Table 3. Weingartner’s (1986) hypothesis potentially could be important in examining the conflicting data on depression and cognition, and it remains to be further tested. In Table 4 three studies demonstrate the confounding of dementia that is superimposed on depressed subjects. All three studies screened for dementia. The Pearson et al. (1989) and Breen et al. (1984) studies show that the cognitive differences between a depressed only group and a depressed plus demented group are not significantly different. However, Pearlson et al. (1989) showed that when the two groups are separately compared to a normal control group, then group differences do emerge. No significant differences between a control and a depressed group were obtained in the Boston Naming Task and the Rey Auditory Verbal Learning Task. However, significant differences were obtained when the control group was compared to the depressed group with detectable dementia. These studies show that if dementia is not screened and is present in the depressed group, then the difference between a depressed group and a normal control group could be magnified.
Weingartner et al., 1977
Authors
Ham D
> 20
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Exper (D) 10 community normals
Control (C)
Subjects
No
Dementia Assessed/Matched Age, Ed, IQ? Processes Effortdemanding number recalled C: 7.1 16.1 Automatic number recalled C: 3.1 20.4
Retrieval effortdemanding C: 9.9 Automatic C: 13.6
Processes Effortdemanding number recalled D: 4.0 10.6 Automatic number recalled D: 2.6 18.9
Retrieval effortdemanding D: 3.2 Automatic D: 12.2
Effort-demanding processes
Automatic processes
Automatic 1. Retrieval recognition
1. Free recall
Effort-demanding retrieval
Remembering highly related words
Processing source
processing 2. Remember related words
1. Semantic
Control
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TABLE 3. Task Effects
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Dementia-Yes
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,?Age = 68.3 +- 1.2 (C)
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Control (C)
1 1 inpatient major depressives DSM-111
Exper (D)
Subjects
MMSE
Rey Auditory Verbal Learning Task
Boston Naming Task
Tasks
TABLE 4. DepressiodDernentia Effect
Control
DOD: 19.0 D: 15.2
MMSE 1.25
.70*
DOD: 4.5 C: 6.4
.81*
.88*
.92
C: 29.0
C: 29.0
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REY lmmediate Recall Number Recalled C: 6.4 D: 5.9
DOD 23.4
D: 25.4
BNT Number Correct
Exper
Magnitude Change * = Signif. Difference
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68.9 +- 5.5 13 community unipolar, major depressives with no memory complaint
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Exper (D)
Control (C)
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= f - 5.2
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Subjects
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Rating Scale Age-No Ed-No
IQ-NO
Ed-No
Age-Yes
MMSE, neurological tests
Rivermead Behavioral
DRS
WAIS
Task: 1. Serial Recall
Mattis Dementia
IQ-NO Dementia-Yes
Brown-Peterson
Tasks
Dementia-Yes
Dementia Assessed/Matched Age, Ed, IQ?
TABLE 5. No Depression Effect
Control
DRS DNC: 139.8NC: 139.8 DC: 139.3 C: 136.9 DVC: 136.3VC: 137.1
WAIS RQ DNC: 113.8NC: 116.4 DC: 111.8 C: 112.3 DVC: 102.8VC: 111.1
Free Recall Percent Correct D: 96.2 C: 97.9
Serial Recall Percent Correct D: 89.7 C: 90.1
Exper
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Magnitude Change * = Signif. Difference h)
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Popkin et al., 1982
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67.7 +- 6.0 20 depressed patients
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23 “Not Currentiy Mentally III” community volunteers
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Ed-No IQ-NO
Physician Age-Yes
Dementia-Yes
IQ-NO
Ed-Yes
Age-Yes
Folstein MMSE
Dementia-Yes
Delayed Recognition (DRG) Continuous Recognition Procedure
Delayed Recall (DR)
Paragraph Recall (PR)
Immediate Recall OR)
Memory Test
False Negative D: 7.45 C: 12.3
CRP Number Correct D: 38.5 C:48.0
DRG D: 17.9 C: 18.2
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Finally, Table 5 presents four studies that show no depression effects on cognitive performances. All four studies screened for the presence of dementia and used normal subjects as controls. If the hypothesis of minimal group effect when no dementia is present is correct (based on the Pearlson et al. study in Table 4),then no group differences should be reported. This is the case with these four studies. In general, the levels of performances of the depressed groups (with the exception of one measure) are about 90%+ of the normals, and in some cases are equal or better.
Summary This brief review of the literature exposed a number of methodological and design weaknesses in published papers on depression and cognition research. Given the magnitude of depression effect size and the sensitivity of depression to confounding by sampling and task variables, it is understandablethat conflicting results have emerged.
DIFFERENTIATING DEPRESSION AND DEMENTIA As noted earlier, one of the primary reasons depression is frequently assessed when
evaluating possible organic dementia is that severe depression may imitate or mask symptoms of dementia. Some clinicians feel that assessment of depression is important, and this practice is commonly employed in clinical assessment. This section will first review selected results of symptom ratings, mini-mental examination scores, and fine grain analysis of episodic, semantic, and constructive memory that successfully differentiated depression from dementia in elderly adults. A second part of this section will introduce an analytic technique that extends our current state-of-the-art from discrete task analysis to pattern or profile analysis of performance characteristics of depressed but not demented, demented but not depressed, and healthy elderly control subjects.
Symptom Ratings The N M H collaborativestudy of drug treatment in depression (Raskin et al., 1982) provided data that symptoms of dementia and depression are clearly differentiable. Recall the data presented in Table 1: Psychiatrists and psychologists rated the depressed symptoms on demented and nondemented individuals who are either depressed or not depressed (Raskin, 1986).The depressed subjects were moderately to severely depressed. Examination of the item scores shows that the raters could discriminatesymptoms of demented from nondemented subjects.Further,demented and nondepressed subjects could be differentiated from nondemented and depressed subjects. This finding shows that when an experienced clinician examines the appropriate signs, it is possible to differentiate depression from dementia.
Cognitive Functioning in Geriatric Depression
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TABLE 6. Significant Differences Among Groups on Selected Items from the Mini-Mental Status Examination (Geriatric Test Battery File) (Adapted from Raskin, 1986) Demented
Item Knows date Knows country Can count backward from 100 by 7s to 72 Can recall “ball” Can recall “flag” Can recall “tree” Can repeat, “No if, ands, or buts” Total score
Nondemented
(1) (2) (3) (4) Depressed Nondepressed Depressed Normal Subjects ( n = 13) ( n = 19) (n = 24) (n = 150)
X2
46 38 45
53 21 53
79 83 87
90 87 71
29.70* * 53.24*” 8.60*
23 8 15 62
21 5 16 68
50 17 21 88
83 52 52 88
50.75** 29.42** 19.58** 10.53*
19.08
20.32
25.54
26.43
45.16**‘
Note: Scores indicate the percentage of subjects in each group attaining correct scores. ‘This is the value of F , not x2. * p = < .05, two-tailed. **p < .01, two-tailed.
Table 6 shows the Mini-Mental Status Examination scores for the same subjects (Raskin, 1986). The demented patients performed more poorly than the depressed or normal subjects. No significant difference was found between the depressed and nondepressed demented subjects. Significant differences were found between nondemented depressed subjects and the normal comparison group on the three recall items. The results show that dementia and depression exert different levels of influence on cognition. Dementia has a significantly greater detrimental effect; depression adds little to the cognitive decline of the subject in early stages of dementia.
Episodic, Semantic, and Constructive Memory Niederehe (1986) reported on a study that systematically examined differences in episodic, semantic, and constructive memory of depressed, demented, and healthy elderly. The study compared depressed outpatients with normal control subjects at both young (ages20 to45) and old (ages 55 to 80) age levels. There were 24 subjects in each of the four groups. A smaller group of 12 elderly patients with neuropsychological profiles suggestive of mild to moderate dementia was also tested. All subjects were screened for depression, health, sensory acuity, and neuropsychology and were matched on education, IQ, and health.
L.W.Poon
256
In episodic memory, subjects viewed lists of 40 high-frequency nouns that fell into 10taxonomiccategories comprising four nouns each. After each list was shown, free recall, cued recall, and recognition were tested in succession to see if retrieval processes affected performancedifferentially among the groups. Semantic memory was measured by the free recall, cued recall, and recognitionof familiarinformation stored in tertiary or remote memory. Constructive memory was measured by the recall of two passages of prose narratives, each about 370 words long. The performance profiles of episodic and semantic memory in Figures 1 and 2 are very similar. In episodic memory, there is no difference between the old controls and old depressed subjects, while the performance patterns are parallel in semantic memory. In both cases, the old organically impaired subjects are significantly impaired and characteristically different from the other four groups. The data from constructive memory based on the recall of stones are different. There are no quantitative differences in the recall of story units among the five groups. However, Figure 3 shows that there is substantial qualitative difference in the manner the story units were recalled. Again, the old organically impaired subjects were significantly different from the old depressed subjects, and both
m I
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Free Recall
Recall
I
rn
cued Recognition
Figure 1. Episodic memory task performance under spontaneous encoding condition as a function of remeval mode and five subject groups. (Adapted from Niederehe, 1986)
257
Cognitive Functioning in Geriatric Depression
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Old CooIra
Young
Conirol Young Deoressw SuBpCIs
Free Recall
cued Recall
Recognition
Figure 2. Performance on core subscale of semantic memory task (memory for world knowledge) as a function of retrieval mode and five subject groups. (adapted from Niederehe, 1986
groups are different from the young and old depressed and the old controls. Using these dependent measures, one can differentiate the old depressed subjects from controls, as well as differentiate the old depressed from the old organically impaired subjects.
Summary This review demonstrates that cognitive differences between early stages of dementia and moderate-to-severe depression can be differentiated using symptom ratings, mini-mental examination items, fine grained analyses of memory performances, and other cognitive measures, as well. There is no doubt that dementia exerts a profound detrimental effect on cognitive functioning. It is also clear that depression would not provide appreciable additive effect on cognitive functioning in patients already diagnosed with early stages of dementia. The notion of a pseudodementia-depression imitating symptoms of dementia-is misleading; cognitive patterns derived from depression are neither pseudo nor imitative of dementia. Use of the term should be abandoned (McAllister, 1981; Reifler, 1982; Shaberg, 1978).
258
L. W.Poon
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;
Young Control SuOmts
-
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0
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f
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Complete Omissions
Partial Omissions
0
Figure 3. Omission of story grammar units in constructive memory task (Story J) as a function of omission type and five subject groups. (Adapted from Niederehe, 1986)
TOWARD AN UNDERSTANDING OF THE DEPRESSIVE COGNITION PROFILE Virtually all the research on cognitive functions in geriatric psychopathology (and psychopathology in the general population) has been conducted on discrete cognitive tasks (see Poon et al., 1986, for a review on depression and dementia). That is, the cognitive performances of patient and control groups have been compared on one or several independent cognitive tasks. Conclusions are based on the performance similarities and differences between the experimental and control groups. Every study cited so far in this paper employs this methodology. Not captured in this methodology is the assessment of the interrelationship between and among the tasks and the appreciation (and prediction) of how the tasks are differentially affected by the psychopathology under investigation. Weingartner (1986), in his assessment of depression research, summarized this state of affairs in the following manner: “Investigators bring to the study of cognitive processes in depression their own ‘favorite’ cognitive theories, models, methods, and procedures, as well as their choices of target cognitive behaviors. If, for example, a researcher is curious about attention, attention is what is studied, often in an isolated fashion, while systems requiring characterization and other types of cognitive and noncognitive behaviors that would also be clinically altered in depression are ignored” (pp. 218-219).
Cognitive Functioning in Geriatric Depression
259
Perhaps our current research methodologies could be improved by studying cognitive profiles constructed from performances in a meaningful cluster of tasks. Systematic changes or movement in the cognitive profile would need to be predicted by theory(ies) or hypotheses. Weingartner himself attempted such an effort (Reus et al., 1979; Weingartner, 1986; see Table 3) when he hypothesized that depression effects would be evident in effort-demanding tasks or situations, but not under easy, superficial, or automatic situations. In formulating his hypothesis, Weingartner (1986) referenced our earlier work on normal aging (Cerella et al., 1980) that demonstrates that age-related cognitive slowing is readily evident in the more demanding types of cognitive tasks. That is, older persons are proportionately slower by a predictable amount on more complex tasks. We have further refined our model to show that performances in the continuum of cognitive tasks within an age group are influenced by a central processor, and that there is an orderly and predictable relationship between aging and cognitive slowing (e.g., Poon, 1989;Myersonet al., 1990).This work was used to support and extend the hypothesis of Birren (Birren, 1965; Birren et al., 1980), who hypothesized that age-related decline in the central nervous system would generalize its effects to all cognitive performances. The next segment of this paper will describe an application of this type of model derived from our attempt to describe and test hypotheses about cognitive performances in normal aging on depression and dementia in older adults. In particular, such a model could answer at least three questions. One, could a parsimonious profile of cognitive performances in depression be constructed? Two, could the profile reflect and substantiate characteristics of depression based on our current knowledge of depression? Three, would it be possible to construct a similar profile for dementia and compare and contrast characteristics of depression and dementia as well as with healthy controls? If these questions could be answered affirmatively then it is possible to use the cognitive profile method to better understand depression and dementia in the geriatric population. The data described below are part of a larger project-"Sleep and EEG discrimination of dementia from depression"-with Patricia Prinz as Principal Investigator. Cognitive performances were measured by three general batteries that evaluated metamemory (self-report of memory functions), psychometric measurements of memory and intelligence, and information-processing reaction time tasks. The data from the information-processing tasks, which took advantage of the ratio scale property of reaction time measurement, are used to construct cognitive profiles.
Subjects Figure 4 describes the inclusion and exclusion criteria used in subject selection. Three groups of subjects (average age 68 years) matched in education and general socioeconomic background were used in the data pertaining to the description of cognitive profiles. Data from 43 subjects were employed in the normal control group, 53 subjects in the depressed but not demented group, and 46 subjects in the demented but not depressed group.
L.W.Poon
260 ~~
INCLUSIONARY CRITERIA FOR GROUP ASSIGNMENTS Normal Control Subjects had no validated memory complaints, no complaints of disturbed sleep, no current physical illness, requiring treatment,no evidenceof current or past psychiatric illness (including MDD), no medication with central nervous system effects 3 weeks prior to the study, and no history of: myocardial infarction or chronic hypertensive cardiovascular disease ETOH, drug abuse neurological disorders chronic renal, hepatic, pulmonary, or endocrine disease syphilis or other disease affecting the central nervous system loss of consciousness due to head trauma, hypoxia or neurotoxins,ECT diabetes Indeterminate Subjects were identical to the normal control group except that they had a complaint of memory problems validated by significant other but did not meet study criteria for the AD group. Alzheimer's Disease, uncomplicated Subjectsmet the inclusionary criteria for the normal controlgroupexceptsubjectswere required to meet the DSM-111criteria for Primary Degenerative Dementia and/or the NINCDS-ADRDA work group (17) diagnosis of possible or probable AD, and have scores 2 20 on the MMS. Major Depressive Disorder Subjects met the inclusionary criteria for the normal conrrol group except they were required to meet RDC (14) for MDD, primary unipolar, nondelusional and were required to have a H R S (12) of 15or greater on the 17-itemscale. No MDD patient met research criteria for AD. Depressed subjects with a prior history of treatment for depression (excluding ECT) were admitted to the study. Figure 4. Criteria used for group assignments. (Adapted from Williams et al., 1988)
Cognitive Tasks and Procedure Attention, decision making, memory retrieval, memory scanning, and semantic processing are five cognitive abilities that have been identified (e.g., DSM-111, APA, 1980) as particularly sensitive to the influences of depression or dementia. These cognitive abilities were measured by five information-processing reaction time tasks: alerting function (Posner & Boies, 1971). four-choice reaction time, continuous recognition memory (Poon & Fozard, 1978), memory scanning (Sternberg, 1969), and semantic processing (Posner & Mitchell, 1967).
261
Cognitive Functioning in GeriatricDepression
continuous recognition memory (Poon & Fozard, 1978), memory scanning (Sternberg, 1969), and semantic processing (Posner & Mitchell, 1967).
Cognitive Profiles Cognitive profiles were constructed by using a “Brinley plot” technique (Brinley, 1965). That is, the performances of an experimental group (e.g., depressed or demented group) are plotted against the control group (e.g., healthy elderly group) for each of the 25 performance means obtained from the five informationprocessing tasks. Two sets of Brinley plots wereobtained. The first compared mean cognitive performances between the demented subjects and controls, and the second compared depressed subjects and controls. Three readily evident observations can be made about these cognitive profiles. One, each of these profiles can be described by alinear regression that accounts for greater than 98% of the variance. Two, the slope (1.29) of the cognitive functions of the demented subjects is significantly higher than that obtained from the depressed subjects (1.06), t(23) = 5.88, p
Toward an Understanding of Cognitive Functioning in Geriatric Depression Leonard W. Poon ABSTRACT. This paper addresses the questions of whether depression compromises cognition in the elderly and whether discernable patterns of cognitive performances could be differentiated between patients with severe depression and those with organic dementia. Published data on geriatric depression and cognitive functioning are divided in demonstrating a depression effect. Further examinationand external validation by new data show that the depression effect on discrete cognitive tasks is (1) small, and (2) sensitive to the confounding of sampling and task variables. Future research must take these factors into account. Patterns of cognitivefunctioning in depression and dementia are different and can be differentiated using a variety of measures. This review finds the term pseudodementiainappropriateand misleading and recommends that it be abandoned.
The purpose of this paper is to address two frequently asked questions about geriatric depression. One, does depression compromise cognitive functioning in older individuals? Two, are there discernable patterns of cognitive performances that differentiatepatients with severedepression from those with organic dementia? Answers to these two questions carry implications for clinical, research, and theoretical domains. From an empirical research perspective, data from published literature can be divided into two camps -those that demonstrated a depression effect on cognition and those that did not. This paper will review a sample of published data from both camps and attempt to isolate relevant factors that could contribute to the disparate findings. When viewed from a clinical diagnostic perspective, depression is assessed on a routine basis when evaluating organic brain disorders.The reason is that depression in the elderly could produce sufficient cognitive impairment - a “pseudodementia” (Kiloh, 1961) - that could be misdiagnosed as an organic dementia. This paper will review quantitative data based on discrete cognitive performances as well as cognitive profiles, combining several cognitive tasks to see ifcognitive performancesin depression and dementia are discernable. Finally, based on the evidence reviewed, this paper will summarize From the Gerontology Center, University of Georgia, Athens, Georgia, U.S.A. (L. W. Poon, PhD)
241
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the necessary and sufficient conditions that must be present for depression to influence cognition in elderly individuals.
CLINICAL SYNDROME OF DEPRESSION Clinical depression refers to a cluster of symptoms in which the primary characteristic is dysphoria, a feeling of being sad, downhearted, or blue. The American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM-111; APA, 1980) and the Research Diagnostic Criteria (RDC; Spitzer et al., 1978) identified the following three key features in depression. One, a duration of at least two weeks must be established for both mood and symptomatic disturbances. Two, the primary feeling state during the episode must be identified. Three, at least four (DSM-111) to five (RDC) of the following symptoms must be present nearly every day of the episode in question if the patient is to be diagnosed with major depression. Two of the following symptoms must be present in order to be diagnosed with minor depression. Poor appetite or significant weight loss, or increased appetite or significant weight gain Insomnia or hypersomnia Psychomotor agitation or retardation Anhedonia Loss of energy, fatiguability, or tiredness Feelings of self-reproach and excessive or inappropriate guilt Complaints or evidence of diminished ability to think or concentrate Recurrent thoughts of death or suicide, wishes to be dead, or evidence of suicidal behavior Evidence of functional impairment, or taking medication, or seeking help for the disorder. For the classification of different subtypes of depression see DSM-I11 (APA, 1980, pp. 218-223).
THE EFFECTS OF DEPRESSION ON COGNITIVE PERFORMANCES Prior to reviewing the effects of depression on cognitive performances of elderly adults, it should be noted that depression has been found to correlate strongly with frequency of memory complaints (e.g., Kahn et al., 1975; Popkin et al., 1982; Zarit et al., 1981), but neither depression nor complaint has been related to the level of memory performances. This has led some investigators to postulate that depressed patients are poor evaluators of their own clinical symptoms. The relationship among depression, self-assessment, and cognitive performance is an important clinical and research area. However, this area will not be reviewed in this paper.
Cognitive Functioning in Geriatric Depression
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Presumably, clinical symptoms identified in depression would predict adverse effects on attention, concentration, motivation, learning, memory, and decisionmaking performances. However, empirical evidence presented in the literature is far from supportive of this prediction.
Supportive Evidence Salzman and Gutfreund (1986) provided a concise summary of effects of depression on cognition that is worth repeating here. Decreased acquisition and recall of new information (Breslow et al., 1981; Cohenet al., 1982; Davis & Unruh, 1980;Friedman, 1964; Henry et al., 1973; Jarvik et al., 1972); increased emrsof omission (Henry et al., 1973;Jarviket al., 1972;McAllister, 1981; Whitehead, 1973); transposition errors, mispairing, and reversal of stimulus-response words (Henry et al., 1973; Whitehead, 1973); decreased ability to impose organization on unorganized information (Breslow et al., 1981; Weingartner et al., 1981, 1982); less effective coding and memory strategies (level of processing) (Breslow et al., 1981; Weingartner et al., 1981, 1982); fluctuating deficits in episodic memory; increased access to sad memories (Bower, 1981; Fogarty & Hemsley, 1983; Isenet al., 1978; Natale & Hantas, 1982; Teasdale & Fogarty, 1979)and, with increasing depression, decreased access to pleasant memories (Breslow et al., 1981); altered guessing strategies; taking fewer risks in a task (Miller & Lewis, 1977), reluctanceto give oneself the benefit of the doubt (Alloy & Abramson, 1979),or reluctance to use negative feedback as a basis for change in strategy (Silberman et al., 1983); and decreased attention and reaction time (Breslow et al., 1981; Cohen et al., 1982; Glass et al., 1981). The large number of studies that showed the detrimental effects of depression on cognition led Weingartner (1986) to conclude that every conceivable stage or type of information-processing system has been implicated in determining aspects of cognitive dysfunction in depression.
Nonsupportive Evidence Given that there are ample data that could differentiate the cognitive performances of depressed elderly from controls, one could postulate that psychiatrists and psychologists who work regularly withdepressivescould easily identify depressives from controls based on cognitive performances. On the contrary, the results are not as straightforward as one would postulate. The not-so-straightforward data came from a large National Institute of Mental Health (NIMH) multihospital collaborative study conceived in the 1960s of drug
244
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treatment in depression (Raskin et al., 1982). A state-of-the-art battery of psychomotor, learning, and perceptual tests was used. The collaborative study sample employed 277 inpatients (17 to 70 years) and 112 normal controls who matched them in age, sex, and education. Thirty-two patients with adiagnosis of progressive idiopathic dementia, senile onset, were included for some of the comparisons. At the time the collaborative study was conceived, one of the investigators had just published a paper that showed either no deficits or small cognitive, perceptual, and psychomotor deficits in 55 severely depressed patients, compared with a matched sample of 65 controls (Friedman, 1964). Fortunately orunfortunately, the outcome of the NIMH collaborative study showed there were significant cognitive differences between depressives and controls. However, the magnitudes of difference between depressed and controls were found to be influenced by the age of the subject, the severity of depression, and the level of education and intelligence. In this instance, the same investigator (Friedman) who had conducted the state-of-theart studies in one of the foremost research centers in the world found opposite results. How could this be? The NIMH investigators (Raskin, 1986) offered a possible explanation that the earlier Friedman (1964) patient samples were above average in verbal abilities, as reflected in their WAIS vocabulary subtest scores, in comparison to the collaborative study samples. Higher IQ tends to moderate the effects of aging and depression on cognitive tests. In this example, we have seen that sample characteristics can profoundly influence the outcome of a study on depression. The concomitant effects of intelligence and education levels within and between comparison samples could under- or overestimate group differences (Poon et al., 1984). Depression is complex, and future research needs to develop a better understanding of the phenomenon as well as methodologies to study it. The NIMH collaborative study also provided data regarding the ease of differentiating depressed from normal subjects.Table 1(from Raskin, 1986)summarizes the ratings of eight items from the Global Assessment of Psychopathology scale. The items represented symptoms that are present in depression. The ratings were conducted by psychiatrists and psychologists on demented and nondemented subjects who were either depressed or nondepressed. Significant discriminations (indicated by significant F ratios) in the ratings of the four samples were obtained. However, examination of the post-hoc analyses showed that the discrimination was obtained between demented and nondemented samples, and not between the depressed and nondepressed samples! The lesson to learn from this data set is that discrimination of depressive signs is not easy, even when undertaken by professionals. Following the conflicting results of the NIMH studies, the literature contains a significant number of studies that showed no cognitive impairments in depressed subjects (e.g., Camp & Niederehe, 1978; Derry & Kuiper, 1981; Golub, 1975; Granick, 1963; Kahn et al., 1975; Kendrick & Post, 1967; Miller & Lewis, 1977; Niederehe, 1986; Niederehe & Camp, 1985; Orme, 1957; Perlin & Butler, 1963; Popkin et al., 1982; Roth & Rehm, 1980).
Cognitive Functioning in Geriatric Depression
245
TABLE 1. Mean Scores Showing Significant Differences Among Groups on Selected Symptoms Rated by Psychiatrists and Psychologists (Geriatric Test Battery File) (Adapted from Raskin, 1986) Demented
Variable Appears confused, perplexed’ Seems disoriented’ Appears inattentive’ Appears forgetful2 Appears depressed, blue’ Appears tense, anxious2 Severity of illness3 Severity of mental deterioration4
Nondemented
(1) (2) (3) (4) Depressed Nondepressed Depressed Normal Subjects ( n = 13) (n = 19) ( n = 24) ( n = 150)
F
Difference
2.46
2.16
1.17
1.12
54.78*
1,2-3,4
2.23 1.23 2.62 3.38 2.23 3.00 2.23
2.16
1.12 1 .oo 1.88 3.54 2.62 2.33 1.67
1.03 1.03 1.19 1.17 1.17 1.11 1.10
57.96** 4.02**
1,2-3,4 1-4,2,3 1 ,2-3-4 3,1-24 3,1-2-4 1-2,34 2.1-3-4
1 .oo
2.42 I .89 1.57 2.47 2.37
51.51**
241.77** 64.41** 108.60** 93.98**
’Groups are listed in order of decreasing scores. A comma indicates no significant difference between scores; a hyphen indicates a significant difference. ’Rated on a 5-point scale from Not at all to Extremely. ‘Rated on a 7-point scale from Normal, not ill at all to Among the most extremely ill patients. “Rated on a 5-point scale from Normnl. shows no signs of deterioration to Among the most deteriorafedpatients. * p < .05, two-tailed. **p < .01, two-tailed.
Summary The literature shows a stalemate on the question of whether depression exerts an adverse effect on the cognitive functions of the elderly. The number of opposing findings make it necessary to examine more intensely our understanding of the mechanisms of depression and their effects on cognitive functioning.
AN ATTEMPT TO MAKE SENSE OF CONFLICTING RESULTS In attempting to understand factors that could possibly contribute to the conflicting results in the literature, Tables 2 to 5 outline four clusters of studies detailing the subject characteristics, cognitive tasks, and magnitudes of depression effects from 12 studies of geriatric depression and cognition. Most of the studies were published between 1985 and 1990. Three general observations are made from examining the 12 studies. First, the studies employ different cognitive tasks that made comparisons across studies difficult. Second, some studies made certain there was no confoundingof dementia and some did not. The possibility that dementia could be superimposed on the depressed and control groups could further confound the conclusions about depression effects. Third, some studies controlled for education and IQ and some did not. These concomitant measures were found to be important in the NIMH collaborative study (Raskind, 1986).
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= 71.0
2 Age
20 normal community residents
Control (C)
20 depressed assessed by psychiatrist No tests listed X Age = 69.0
Exper (D)
Subjects
Gibson, A. J. 1981
Authors
IQ-NO
MSG GAS WAIS Age-Yes Ed.-Yes
Dementia-Yes
IQ-NO
No tests listed Age-Yes Ed. -No
Dementia-Yes
Dementia AssessediMatched Age, Ed, IQ? Tasks
Fuld ObjectMemory Evaluation
Inglis PairedAssociate Learning Test
Benton Visual Retention Test
Immediate free recall of words from Miller (1971) (verbal) Object Learning Test of Revised Kendrick Ballery (Visual)
TABLE 2. Depression Effect
Control
OME Retrieval D: 6.8 C: 9.2 Consistent Retrieval D: 5.3 C: 8.6 Category Retrieval D: 37.0 C: 52.4
PALT Total Correct Responses D: 13.5 C: 14.1 Total Correct Responses D: 6.1 C:10.5
VRT Total Correct D: 3.1 C5.5 Total Errors D: 13.5 C: 7.0 Error TypeOmissions D: 4.0 C: 1.2
Visual Total Recall D: 26.9 C: 38.3
Verbal Total Recall D: 25.7 C: 34.7
Exper
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.56*
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IQ-NO
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Age-Yes
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Ed-No IQ-No
Age-Yes
WMS >80: No dementia
Dementia-Yes
Memory Scanning
Symbol
WAIS Digit
Rey Auditory Verbal Learning Test and Famous Faces Test
8.0 10.9
10.0
9.0 8.2
8.5
7.2
4.0
7.3
6.6
4.4
13.6
C:
52 53 56 55 33
78 81 71 71 67
Memory Scanning Intercept for Mean Reaction Time (MS) D: 870.0 C: 685.0
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Table 2 presents four studies that support the detrimental effects of depression. That is, the performances of the depressed were clearly lower than control (ratio D/ C in the table). For example, the Gibson (1981) study is an unequivocal demonstration of a depression effect on a verbal and a visual task. The age range of the depressed and control groups was matched, and dementia was evaluated to rule out possible confounding. The results show that depressed subjects performed significantly poorer, at about 70% of the performance level of the controls. Similar outcomes are found in the LaRue et al. (1986) study. Although significant depression effects were found in the Benton Visual Retention and the Fuld ObjectMemory tests, a depression effect was not found in the Inglis Paired-Associate Learning test. This is also true in the Sweeney et al. (1989) study where adepression effect was found in the Famous Faces test, but not in the Rey Auditory Verbal Learning test. Although dementia screening was not noted in the Hart and Kwentus (1987) paper, clear group differences were obtained. Since no dementia assessment was made in this study, one should be cautious in interpreting the results, however. Dementia could be present with the depression group that could increase the magnitude of group difference. Table 3 outlines a study by Weingartner et al. (1977) that demonstrates the importance of task selection in the study of depression. Weingartner (1986) postulated that patterns of depression deficit seen in the literature could be a function of the amount of effort demanded from the subject. This effortful dimension is usually not controlled in studies of depression. Depression effect would be more evident in effort-demanding tasks and not obvious in superficial processing and automatic tasks. This postulation is supported by the data shown in Table 3. Weingartner’s (1986) hypothesis potentially could be important in examining the conflicting data on depression and cognition, and it remains to be further tested. In Table 4 three studies demonstrate the confounding of dementia that is superimposed on depressed subjects. All three studies screened for dementia. The Pearson et al. (1989) and Breen et al. (1984) studies show that the cognitive differences between a depressed only group and a depressed plus demented group are not significantly different. However, Pearlson et al. (1989) showed that when the two groups are separately compared to a normal control group, then group differences do emerge. No significant differences between a control and a depressed group were obtained in the Boston Naming Task and the Rey Auditory Verbal Learning Task. However, significant differences were obtained when the control group was compared to the depressed group with detectable dementia. These studies show that if dementia is not screened and is present in the depressed group, then the difference between a depressed group and a normal control group could be magnified.
Weingartner et al., 1977
Authors
Ham D
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Exper (D) 10 community normals
Control (C)
Subjects
No
Dementia Assessed/Matched Age, Ed, IQ? Processes Effortdemanding number recalled C: 7.1 16.1 Automatic number recalled C: 3.1 20.4
Retrieval effortdemanding C: 9.9 Automatic C: 13.6
Processes Effortdemanding number recalled D: 4.0 10.6 Automatic number recalled D: 2.6 18.9
Retrieval effortdemanding D: 3.2 Automatic D: 12.2
Effort-demanding processes
Automatic processes
Automatic 1. Retrieval recognition
1. Free recall
Effort-demanding retrieval
Remembering highly related words
Processing source
processing 2. Remember related words
1. Semantic
Control
Exper
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Control (C)
1 1 inpatient major depressives DSM-111
Exper (D)
Subjects
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Boston Naming Task
Tasks
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Control
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.70*
DOD: 4.5 C: 6.4
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C: 29.0
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REY lmmediate Recall Number Recalled C: 6.4 D: 5.9
DOD 23.4
D: 25.4
BNT Number Correct
Exper
Magnitude Change * = Signif. Difference
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68.9 +- 5.5 13 community unipolar, major depressives with no memory complaint
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Exper (D)
Control (C)
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Rating Scale Age-No Ed-No
IQ-NO
Ed-No
Age-Yes
MMSE, neurological tests
Rivermead Behavioral
DRS
WAIS
Task: 1. Serial Recall
Mattis Dementia
IQ-NO Dementia-Yes
Brown-Peterson
Tasks
Dementia-Yes
Dementia Assessed/Matched Age, Ed, IQ?
TABLE 5. No Depression Effect
Control
DRS DNC: 139.8NC: 139.8 DC: 139.3 C: 136.9 DVC: 136.3VC: 137.1
WAIS RQ DNC: 113.8NC: 116.4 DC: 111.8 C: 112.3 DVC: 102.8VC: 111.1
Free Recall Percent Correct D: 96.2 C: 97.9
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Ed-No IQ-NO
Physician Age-Yes
Dementia-Yes
IQ-NO
Ed-Yes
Age-Yes
Folstein MMSE
Dementia-Yes
Delayed Recognition (DRG) Continuous Recognition Procedure
Delayed Recall (DR)
Paragraph Recall (PR)
Immediate Recall OR)
Memory Test
False Negative D: 7.45 C: 12.3
CRP Number Correct D: 38.5 C:48.0
DRG D: 17.9 C: 18.2
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L.W . Poon
Finally, Table 5 presents four studies that show no depression effects on cognitive performances. All four studies screened for the presence of dementia and used normal subjects as controls. If the hypothesis of minimal group effect when no dementia is present is correct (based on the Pearlson et al. study in Table 4),then no group differences should be reported. This is the case with these four studies. In general, the levels of performances of the depressed groups (with the exception of one measure) are about 90%+ of the normals, and in some cases are equal or better.
Summary This brief review of the literature exposed a number of methodological and design weaknesses in published papers on depression and cognition research. Given the magnitude of depression effect size and the sensitivity of depression to confounding by sampling and task variables, it is understandablethat conflicting results have emerged.
DIFFERENTIATING DEPRESSION AND DEMENTIA As noted earlier, one of the primary reasons depression is frequently assessed when
evaluating possible organic dementia is that severe depression may imitate or mask symptoms of dementia. Some clinicians feel that assessment of depression is important, and this practice is commonly employed in clinical assessment. This section will first review selected results of symptom ratings, mini-mental examination scores, and fine grain analysis of episodic, semantic, and constructive memory that successfully differentiated depression from dementia in elderly adults. A second part of this section will introduce an analytic technique that extends our current state-of-the-art from discrete task analysis to pattern or profile analysis of performance characteristics of depressed but not demented, demented but not depressed, and healthy elderly control subjects.
Symptom Ratings The N M H collaborativestudy of drug treatment in depression (Raskin et al., 1982) provided data that symptoms of dementia and depression are clearly differentiable. Recall the data presented in Table 1: Psychiatrists and psychologists rated the depressed symptoms on demented and nondemented individuals who are either depressed or not depressed (Raskin, 1986).The depressed subjects were moderately to severely depressed. Examination of the item scores shows that the raters could discriminatesymptoms of demented from nondemented subjects.Further,demented and nondepressed subjects could be differentiated from nondemented and depressed subjects. This finding shows that when an experienced clinician examines the appropriate signs, it is possible to differentiate depression from dementia.
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TABLE 6. Significant Differences Among Groups on Selected Items from the Mini-Mental Status Examination (Geriatric Test Battery File) (Adapted from Raskin, 1986) Demented
Item Knows date Knows country Can count backward from 100 by 7s to 72 Can recall “ball” Can recall “flag” Can recall “tree” Can repeat, “No if, ands, or buts” Total score
Nondemented
(1) (2) (3) (4) Depressed Nondepressed Depressed Normal Subjects ( n = 13) ( n = 19) (n = 24) (n = 150)
X2
46 38 45
53 21 53
79 83 87
90 87 71
29.70* * 53.24*” 8.60*
23 8 15 62
21 5 16 68
50 17 21 88
83 52 52 88
50.75** 29.42** 19.58** 10.53*
19.08
20.32
25.54
26.43
45.16**‘
Note: Scores indicate the percentage of subjects in each group attaining correct scores. ‘This is the value of F , not x2. * p = < .05, two-tailed. **p < .01, two-tailed.
Table 6 shows the Mini-Mental Status Examination scores for the same subjects (Raskin, 1986). The demented patients performed more poorly than the depressed or normal subjects. No significant difference was found between the depressed and nondepressed demented subjects. Significant differences were found between nondemented depressed subjects and the normal comparison group on the three recall items. The results show that dementia and depression exert different levels of influence on cognition. Dementia has a significantly greater detrimental effect; depression adds little to the cognitive decline of the subject in early stages of dementia.
Episodic, Semantic, and Constructive Memory Niederehe (1986) reported on a study that systematically examined differences in episodic, semantic, and constructive memory of depressed, demented, and healthy elderly. The study compared depressed outpatients with normal control subjects at both young (ages20 to45) and old (ages 55 to 80) age levels. There were 24 subjects in each of the four groups. A smaller group of 12 elderly patients with neuropsychological profiles suggestive of mild to moderate dementia was also tested. All subjects were screened for depression, health, sensory acuity, and neuropsychology and were matched on education, IQ, and health.
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In episodic memory, subjects viewed lists of 40 high-frequency nouns that fell into 10taxonomiccategories comprising four nouns each. After each list was shown, free recall, cued recall, and recognition were tested in succession to see if retrieval processes affected performancedifferentially among the groups. Semantic memory was measured by the free recall, cued recall, and recognitionof familiarinformation stored in tertiary or remote memory. Constructive memory was measured by the recall of two passages of prose narratives, each about 370 words long. The performance profiles of episodic and semantic memory in Figures 1 and 2 are very similar. In episodic memory, there is no difference between the old controls and old depressed subjects, while the performance patterns are parallel in semantic memory. In both cases, the old organically impaired subjects are significantly impaired and characteristically different from the other four groups. The data from constructive memory based on the recall of stones are different. There are no quantitative differences in the recall of story units among the five groups. However, Figure 3 shows that there is substantial qualitative difference in the manner the story units were recalled. Again, the old organically impaired subjects were significantly different from the old depressed subjects, and both
m I
I m
Free Recall
Recall
I
rn
cued Recognition
Figure 1. Episodic memory task performance under spontaneous encoding condition as a function of remeval mode and five subject groups. (Adapted from Niederehe, 1986)
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I
Old CooIra
Young
Conirol Young Deoressw SuBpCIs
Free Recall
cued Recall
Recognition
Figure 2. Performance on core subscale of semantic memory task (memory for world knowledge) as a function of retrieval mode and five subject groups. (adapted from Niederehe, 1986
groups are different from the young and old depressed and the old controls. Using these dependent measures, one can differentiate the old depressed subjects from controls, as well as differentiate the old depressed from the old organically impaired subjects.
Summary This review demonstrates that cognitive differences between early stages of dementia and moderate-to-severe depression can be differentiated using symptom ratings, mini-mental examination items, fine grained analyses of memory performances, and other cognitive measures, as well. There is no doubt that dementia exerts a profound detrimental effect on cognitive functioning. It is also clear that depression would not provide appreciable additive effect on cognitive functioning in patients already diagnosed with early stages of dementia. The notion of a pseudodementia-depression imitating symptoms of dementia-is misleading; cognitive patterns derived from depression are neither pseudo nor imitative of dementia. Use of the term should be abandoned (McAllister, 1981; Reifler, 1982; Shaberg, 1978).
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20
Ywng Depressed Subiecta
Y)
0
Old Conlrol SuQects
;
Young Control SuOmts
-
0
0
L n
Old Depressed Su0)ecls
f
z
10 Old Organically Impaired SUQeclS
Complete Omissions
Partial Omissions
0
Figure 3. Omission of story grammar units in constructive memory task (Story J) as a function of omission type and five subject groups. (Adapted from Niederehe, 1986)
TOWARD AN UNDERSTANDING OF THE DEPRESSIVE COGNITION PROFILE Virtually all the research on cognitive functions in geriatric psychopathology (and psychopathology in the general population) has been conducted on discrete cognitive tasks (see Poon et al., 1986, for a review on depression and dementia). That is, the cognitive performances of patient and control groups have been compared on one or several independent cognitive tasks. Conclusions are based on the performance similarities and differences between the experimental and control groups. Every study cited so far in this paper employs this methodology. Not captured in this methodology is the assessment of the interrelationship between and among the tasks and the appreciation (and prediction) of how the tasks are differentially affected by the psychopathology under investigation. Weingartner (1986), in his assessment of depression research, summarized this state of affairs in the following manner: “Investigators bring to the study of cognitive processes in depression their own ‘favorite’ cognitive theories, models, methods, and procedures, as well as their choices of target cognitive behaviors. If, for example, a researcher is curious about attention, attention is what is studied, often in an isolated fashion, while systems requiring characterization and other types of cognitive and noncognitive behaviors that would also be clinically altered in depression are ignored” (pp. 218-219).
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Perhaps our current research methodologies could be improved by studying cognitive profiles constructed from performances in a meaningful cluster of tasks. Systematic changes or movement in the cognitive profile would need to be predicted by theory(ies) or hypotheses. Weingartner himself attempted such an effort (Reus et al., 1979; Weingartner, 1986; see Table 3) when he hypothesized that depression effects would be evident in effort-demanding tasks or situations, but not under easy, superficial, or automatic situations. In formulating his hypothesis, Weingartner (1986) referenced our earlier work on normal aging (Cerella et al., 1980) that demonstrates that age-related cognitive slowing is readily evident in the more demanding types of cognitive tasks. That is, older persons are proportionately slower by a predictable amount on more complex tasks. We have further refined our model to show that performances in the continuum of cognitive tasks within an age group are influenced by a central processor, and that there is an orderly and predictable relationship between aging and cognitive slowing (e.g., Poon, 1989;Myersonet al., 1990).This work was used to support and extend the hypothesis of Birren (Birren, 1965; Birren et al., 1980), who hypothesized that age-related decline in the central nervous system would generalize its effects to all cognitive performances. The next segment of this paper will describe an application of this type of model derived from our attempt to describe and test hypotheses about cognitive performances in normal aging on depression and dementia in older adults. In particular, such a model could answer at least three questions. One, could a parsimonious profile of cognitive performances in depression be constructed? Two, could the profile reflect and substantiate characteristics of depression based on our current knowledge of depression? Three, would it be possible to construct a similar profile for dementia and compare and contrast characteristics of depression and dementia as well as with healthy controls? If these questions could be answered affirmatively then it is possible to use the cognitive profile method to better understand depression and dementia in the geriatric population. The data described below are part of a larger project-"Sleep and EEG discrimination of dementia from depression"-with Patricia Prinz as Principal Investigator. Cognitive performances were measured by three general batteries that evaluated metamemory (self-report of memory functions), psychometric measurements of memory and intelligence, and information-processing reaction time tasks. The data from the information-processing tasks, which took advantage of the ratio scale property of reaction time measurement, are used to construct cognitive profiles.
Subjects Figure 4 describes the inclusion and exclusion criteria used in subject selection. Three groups of subjects (average age 68 years) matched in education and general socioeconomic background were used in the data pertaining to the description of cognitive profiles. Data from 43 subjects were employed in the normal control group, 53 subjects in the depressed but not demented group, and 46 subjects in the demented but not depressed group.
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INCLUSIONARY CRITERIA FOR GROUP ASSIGNMENTS Normal Control Subjects had no validated memory complaints, no complaints of disturbed sleep, no current physical illness, requiring treatment,no evidenceof current or past psychiatric illness (including MDD), no medication with central nervous system effects 3 weeks prior to the study, and no history of: myocardial infarction or chronic hypertensive cardiovascular disease ETOH, drug abuse neurological disorders chronic renal, hepatic, pulmonary, or endocrine disease syphilis or other disease affecting the central nervous system loss of consciousness due to head trauma, hypoxia or neurotoxins,ECT diabetes Indeterminate Subjects were identical to the normal control group except that they had a complaint of memory problems validated by significant other but did not meet study criteria for the AD group. Alzheimer's Disease, uncomplicated Subjectsmet the inclusionary criteria for the normal controlgroupexceptsubjectswere required to meet the DSM-111criteria for Primary Degenerative Dementia and/or the NINCDS-ADRDA work group (17) diagnosis of possible or probable AD, and have scores 2 20 on the MMS. Major Depressive Disorder Subjects met the inclusionary criteria for the normal conrrol group except they were required to meet RDC (14) for MDD, primary unipolar, nondelusional and were required to have a H R S (12) of 15or greater on the 17-itemscale. No MDD patient met research criteria for AD. Depressed subjects with a prior history of treatment for depression (excluding ECT) were admitted to the study. Figure 4. Criteria used for group assignments. (Adapted from Williams et al., 1988)
Cognitive Tasks and Procedure Attention, decision making, memory retrieval, memory scanning, and semantic processing are five cognitive abilities that have been identified (e.g., DSM-111, APA, 1980) as particularly sensitive to the influences of depression or dementia. These cognitive abilities were measured by five information-processing reaction time tasks: alerting function (Posner & Boies, 1971). four-choice reaction time, continuous recognition memory (Poon & Fozard, 1978), memory scanning (Sternberg, 1969), and semantic processing (Posner & Mitchell, 1967).
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continuous recognition memory (Poon & Fozard, 1978), memory scanning (Sternberg, 1969), and semantic processing (Posner & Mitchell, 1967).
Cognitive Profiles Cognitive profiles were constructed by using a “Brinley plot” technique (Brinley, 1965). That is, the performances of an experimental group (e.g., depressed or demented group) are plotted against the control group (e.g., healthy elderly group) for each of the 25 performance means obtained from the five informationprocessing tasks. Two sets of Brinley plots wereobtained. The first compared mean cognitive performances between the demented subjects and controls, and the second compared depressed subjects and controls. Three readily evident observations can be made about these cognitive profiles. One, each of these profiles can be described by alinear regression that accounts for greater than 98% of the variance. Two, the slope (1.29) of the cognitive functions of the demented subjects is significantly higher than that obtained from the depressed subjects (1.06), t(23) = 5.88, p
