J. DRUG EDUCATION, Vol. 20(4) 319-328,1990

CAFFEINE CONSUMPTION, EXPECTANCIES OF CAFFEINE-ENHANCED PERFORMANCE, AND CAFFEINISM SYMPTOMS AMONG UNIVERSITY STUDENTS

JOHN R. BRADLEY ALLEN PETREE

Universityof Montana

ABSTRACT

The expectancies paradigm developed in alcohol research was used to study caffeine consumption and signs of caffeinism in two groups of college students. A survey questionnaire was developed to gather self-report data on expectations of caffeine-enhanced performance (EP-CAFF). level of beverage caffeine consumed daily, and DSM-111 caffeinism signs reportedly experienced after consumption of caffeinated beverages. A positive association between EP-CAFF and both caffeine consumption and caffeinism signs was predicted. In both initial (n = 527) and cross-validation (n = 270) samples, significant correlations between EP-CAFF scores and both caffeine consumption and caffeinism symptoms were found. A small, but statistically significant, relationship was also found between caffeinism symptoms and both alcohol consumption and cigarette smoking. Of the 797 subjects in the combined sample, 151 (18.9%) endorsed five or more DSM-111 caffeinism signs. Subjects endorsing five or more signs of caffeinism scored higher on the EP-CAFF scale, and consumed more caffeine and alcohol in both studies and smoked more cigarettes in study one-but not in study two-than did subjects who endorsed fewer than five caffeinism signs. Results support the utility of extending the expectancies model of substance use motivation from alcohol to caffeine.

Recent psychological formulations of substance use and abuse have increasingly pointed to motivational commonalities across diverse classes of drugs. Similar motives for the use of different drugs is evident in current analyses of biochemical 319

0 1990,Baywood Publishing Co., Inc.

doi: 10.2190/R64X-UEMW-HE3Y-UUNA http://baywood.com

320 1 BRADLEY AND PETREE

mechanisms of drug reinforcement [l]and the expectancies held by substance users about the intended effects of use [2]. The present report extends a motivational model developed to study alcohol use-expctancies regarding effects-to another widely used drug, caffeine. WHY STUDY MOTIVES FOR CAFFEINE USE?

Besides the possible heuristic gain of extending the expectancies construct from alcohol use to caffeine consumption, interest in caffeine is motivated by clinical pragmatism. Caffeine consumption is ubiquitous in our society. The potential adverse effects of caffeine consumption have become the focus of increasing attention in recent years. The American Psychiatric Association has added caffeinism (caffeinism intoxication) to its Diagnostic and Statistical Manual of Mental Disorders [31. The caffeinism syndrome includes autonomic signs, diuresis, gastrointestinal disturbances, insomnia, and symptoms mimicking anxiety disorders. Caffeine-induced symptoms are of clinical significance in an of themselves. Caffeinism is also a factor which can complicate differential diagnosis of other psychiatric disorders [4, 51, produce additional reversible symptoms in patients with primary psychiatric disorders [6],or form part of a constellation of multiplesubstance use [7]. Another potential concern regarding caffeine consumption which could be relevant for college students is the possible association between maternal caffeine consumption and birth outcomes. A review of this literature by Martin found few studies bearing on this topic and inconsistent results in those studies reported [8]. In one carefully controlled examination of neonatal correlates of prenatal exposure to smoking, caffeine, and alcohol, however, Jacobson, Fein, Jacobson, Schwartz, and Dowler identified a positive association between levels of maternal caffeine consumption and shorter gestation time, poorer neuromuscular development, and decreased reflex functioning [9].These findings, if replicated, would bolster the importance of understanding those factors which maintain caffeine consumption in persons of child-bearing age. EXPECTANCIES REGARDING CAFFEINE: A MODEL BORROWED FROM ALCOHOL RESEARCH

In the studies reported below, we investigated the role of expectancies regarding the performance-enhancing effects of caffeine as a motivational factor. Since the expectancies paradigm has been valuable in predicting patterns of problem alcohol consumption (see [lo] for a review), it is potentially useful to develop a caffeine expectancy measure which would predict the extent of caffeine consumption and the Occurrence of caffeinism symptoms.

ENHANCED PERFORMANCE EXPECTANCIES / 321

Leigh notes that defining expectancy scale content areas on a a priori basis, rather than clustering diverse contents together following factor analysis, makes such scales more interpretable [lo]. A prototype of this type of scale is the “drinking function” scale. Contents of such scales define alcohol use in terms of the expected “functions” which alcohol is intended by the drinker to serve [ll]. We adopted a similar approach for development of the expectancy scale for caffeinecontaining beverages reported below.

EXPECTANCIES REGARDING CAFFEINE-ENHANCED PERFORMANCE

Enhanced performance appeared to be an appropriate candidate for an a priori caffeine use motivation scale. For many subjects, caffeine’s effects reflect its stimulant properties. These effects include enhanced psychomotor performance, alertness, and relief of fatigue [12,13]. There is some experimental evidence that college students expect that caffeine will enhance their performance. Flory and Gilbert’s review concluded that placebo effects of caffeine increased college students performance on a variety of tasks [14]. More recently, Kirsch and Weixel used double-blind and deceptive administration protocols to administer decaffeinated coffee [15]. They observed an inverted-U shaped “dose”/response curve in the performance of college student subjects who were deceived to believe that they were consuming varying levels of caffeine and the occurrence of caffeinism symptoms. Kirsch and Weixel’s results clearly point to a behaviorally potent expectancy of caffeine’s enhancement of performance. The aim of the present studies was to develop a scale reflecting beliefs about caffeine’s enhancement of performance with internal consistency and content homogeneity. Based on prior findings linking positive alcohol expectancies, high alcohol consumption, and negative drinking outcomes, it was hypothesized that the extent of endorsement of personal expectancies of performance-enhancing properties of caffeine-containing beverages would be positively related to level of caffeine consumption and number of signs of caffeinism reported by each subject. In additional analyses, as an analogue to DSM-111 classification, subjects were divided into those reporting five or more signs of caffeine intoxication (caffeinism “syndrome present”) and those reporting fewer than five signs (caffeinism “syndrome absent”). These groups were then compared, hypothesizing that the syndrome-present group would have significantly higher caffeine intake and more performanceenhancement expectancies regarding caffeine consumption than the syndrome-absent group. Istivan and Matarazzo have suggested considering the overall patterns of consumption of caffeine, alcohol, and cigarettes in relationship to health outcomes. Measures of the use of cigarettes and alcohol were included in our survey and used

322 I BRADLEYANDPETREE

in exploratory analyses as predictors of caffeinism signs and caffeine intake. Results obtained in our initial study were cross-validated in a second sample.

METHOD

Study One: Subjects and Procedures

Undergraduate student volunteers from the University of Montana and the University of Wyoming participated in the study. University of Montana students received experimental credit for their introductory psychology course. University of Wyoming students agreed to participate as a course experience. Of 560 questionnaires administered, thirty-three were incomplete, improperly filled out, or revealed that the subject did not drink caffeinated beverages. Of the total sample of remaining 527 subjects, 290 were female and 237 were male. The scale used to measure expectancies of enhanced performance from caffeine consumption (EP-CAFF) contained six statements reflecting the following reasons for drinking caffeine-containing beverages: 1. Wake up in the morning; 2. Wake up or stay awake later in the day or evening;

3. Help with study or work; 4. Improve performance; 5. Get energy; and 6. Improve concentration. These items were included along with ten other items written to reflect the use of caffeine containing beverages as food (e.g., tastes good with food, quenches thirst), reflecting social setting use (when visiting with friends), or for use in suppressing appetite. The present article is confined to analysis of the EP-CAFF scale items. This scale’s internal consistency was judged to be adequate: Cronbach’s alpha was .71 for study one and .73for study two. Subjects were asked to describe their caffeinated beverage intake for the month preceding questionnaire administration.Caffeine consumption was measured with a scale which provides a quantity-frequency index for caffeine-containing softdrinks, tea, and coffee adapted from the quantity-frequency measure of alcohol use described by Jessor, Carman, and Grossman [ll].Values assigned for caffeine content of each serving of each.beverage were those included in DSM-111 for soft-drinks (50 milligrams), tea (75 milligrams), and coffee (150 milligrams). These values are the high-range values suggested in DSM-111 (American Psychiatric Association). Average daily total caffeine (TCAFF‘) intake in milligrams was calculated as the sum of caffeine per day from these three beverage sources. Caffeinism signs were presented in checklist form using twelve “diagnostic sign” statements modified for first-person report from the DSM-111 criteria for

ENHANCED PERFORMANCE EXPECTANCIES / 323

caffeine intoxication. Instructions asked subjects to circle the letter next to each item “for each change” they have noticed “after drinking caffeine-containing beverages.” The number of signs endorsed (CAFF-SX) was entered as a continuous variable in correlational and regression analyses. Subjects were divided into groups according to whether or not they endorsed five or more signs of caffeinism (an analogue to the DSM-111 criterion for caffeine intoxication) for group comparisons. Quantity of alcohol intake from all beverage sources, expressed in ounces of absolute alcohol per occasion of use (ETOH-QT) was calculated based upon subjects’ questionnaire responses using the method detailed in Jessor, Carman, and Grossman. The quantity-per occasion parameter was chosen instead of frequency of drinking or average daily quantity consumed because it showed the largest correlation with CAFF-SX. Cigarette smokers were asked to indicate their level of use of cigarettes in increments based on portions of a pack of cigarettes per day which were converted to cigarettes per day (CIGSDAY) for analyses.

Study Two: Subjects and Procedures Subjects were undergraduate psychology students from the University of Montana who volunteered to participate in the study in exchange for experimental credit. Of 303 questionnaires administered, thirty-three were incomplete, improperly filled out, or indicated that the subject did not drink caffeinated beverages. Of the total of 270 remaining subjects, 178 were female and ninety-two were male. Procedures were identical to those reported for study one. RESULTS

No sex differences were observed in either study one or study two for number of caffeinism symptoms (CAFF-SX), caffeine intake (T-CAFF), or cigarettes smoked per day (CIGSDAY). Males did report drinking greater quantities of alcohol per drinking occasion (ETOH-QT) than females in both studies: this difference amounted to the equivalent of an average of just over one ounce of absolute alcohol per occasion (see Table 1). Intercorrelations for all variables in each study are presented in Table 2. As predicted, correlations between the EP-CAFF scale scores and T-CAFF and CAFF-SX were positive and significant in both studies. T-CAFF was significantly correlated with CIGSDAY in study one only. CAFF-SX was correlated significantly with ETOH-QT in both studies, although the magnitude of this relationship was greater in study two. Level of consumption of caffeine was significantly correlated with level of consumption of alcohol and cigarette smoking in both studies.

324 I BRADLEYANDPETREE

Table 1. Group Mean Comparisons of Male vs. Female Subjects

Study 2

Study 1

Male Female (n = 237) (n = 290) CAFF-SX M

SD TCAFF M

SD EP-CAFF M SD ETOH-QT M

SD CIGS/DAY M

SD

t

Male Female (n = 92) (n = 178)

t

2.37 2.1 1

2.38 2.03

-.09

2.95 2.54

2.86

.26 2.34

346.52 289.97

332.24 281.12

.57

358.97 369.11

358.10 257.20

.93

1.31 1.60

1.50 1.53

-1.40

2.05 1.86

1.72 1.56

1.46

5.31 3.09

3.99 2.41

5.41*

5.28 2.81

4.27 2.63

2.93*

1.48 5.38

1.32 4.78

.36

2.44 7.31

1.56 4.92

1.05

Note: CAFF-SX = DSM-111 caffeinism signs endorsed; EP-CAFF = caffeine-enhanced performance scale score; T-CAFF = total daily average beverage caffeine consumption (mgs); ETOH-QT = average quantity (ounces absolute alcohol) consumed per drinking occasion; CIGSDAY = cigarettes consumed per day (includes non-smoker subjects. * p < .05. * p < .01.

Stepwise multiple regression analyses were performed for each study using EP-CAFF, T-CAFF, ETOH-QT, and CIGSDAY as independent variables and CAFF-SX as the dependent variable. Results of these analyses are shown in Table 3. For study one, EP-CAFF, T-CAFF, and CIGSDAY yielded a multiple R of .476 F(2,524) = 76.60,p < .001. For study two, EP-CAFF, ETOH-QT, and T-CAFF yielded a multiple R of .468 F(3,266) = 24.92, p < .001. Though statistically significant due to the large sample size, the additional amount of variance in CAFF-SX beyond that associated with EP-CAFF was small for the other variables in these equations. Group comparisons of subjects classified as caffeinism syndrome-present (n = 87 in study one; n = 64 in study two) and syndrome-absent (n = 440 in study one; n = 206 in study two) are shown in Table 4. In both studies syndrome-present

ENHANCED PERFORMANCE EXPECTANCIES / 325

Table 2. lntercorrelation Matrix Variables

CAFF-SX

EP-CAFF

T-CAFF

ETOH-OT CIGS/DAY

Study One (n = 527)

CAFF-SX EP-CAFF T-CAFF ETOH-QT

.465-

.270m .379-

.lo1 .174.143-

.173* .176.276* .053

.206* .208.089

.066 .026 .31Om .012

Study Two (n = 270)

CAFF-SX EP-CAFF T-CAFF ETOH-QT

.441m

.234.291m

Note: CAFF-SX = DSM-111 caffeinism signs endorsed; EP-CAFF = caffeine-enhanced performance scale score; T-CAFF = total daily average beverage caffeine consumption (mgs); ETOH-QT = average quantity (ounces absolute alcohol) consumer per drinking occasion; CIGS/DAY = cigarettes consumed per day (includes non-smoker subjects). p < .05. - p < .01. - p < .001.

Table 3. Results of Stepwise Multiple Regression Using Number of Caffeinism Signs as the Dependent Variable Variables

Multiple R

R-Squared

Beta

Study One (n = 527) EP-CAFF T-CAFF

.465 .476

.216 226

.423 .lo9

.194 .208 .219

.384 .116 .112

Study Two (n = 270)

EP-CAFF ETOH-QT T-CAFF

.441 .456 .468

Note: CAFF-SX = DSM-111 caffeinism signs endorsed; EP-CAFF = caffeineenhanced performance scale score; T-CAFF = total daily average beverage caffeine consumption (mgs); ETOH-QT = average uantity (ounces absolute alcohol) consumed per drinking occasion; CIGSIDAF = cigarettes consumed per day (includes non-smoker subjects).

326 1 BRADLEYANDPETREE

Table 4. Group Mean Comparisons of Subjects with Five Caffeinism Signs Endorsed, Absent vs. Present Five CaffeinismSigns

study 1 Absent Present (n = 440) (n = 87)

TCAFF M

SD EP-CAFF M SD

study 2 t

Absent Present (n =207) (n = s4)

t

317.67 266.81

444.83 345.80

3.81-

309.10 299.78

408.59 289.95

-2.34*

1.16 1.41

2.70 1.70

-8.98-

1.56 1.60

2.73 1.60

-5.14-

4.47 2.76

5.17 2.99

-2.14*

4.37 2.78

5.40 2.41

-2.68

1.02 4.23

3.22 7.79

3.74-

1.72 5.72

2.30 6.27

-.69

ETOH-QT M

SD CIGS/DAY M SD

Note: CAFF-SX = DSM-111 caffeinism signs endorsed; EP-CAFF = caffeine-enhanced performance scale score; T-CAFF = total daily average beverage caffeine consumption (mgs); ETOH-QT = average quantity (ounces absolute alcohol) consumed per drinking occasion; CIGS/DAY = cigarettes consumed per day (indudes non-smoker subjects). * p < .05. *.p