Research in Developmental Disabilities 35 (2014) 3156–3161
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Research in Developmental Disabilities
Co-occurring disorder clusters in adults with mild and moderate intellectual disability in residential treatment settings Nicole C. Turygin *, Johnny L. Matson, Hilary L. Adams, Lindsey W. Williams Louisiana State University, United States
A R T I C L E I N F O
A B S T R A C T
Article history: Received 8 April 2014 Received in revised form 8 July 2014 Accepted 20 July 2014 Available online
In the typically developing population, co-occurring psychopathology is not uncommon and is a topic of importance among psychologists. It is only recently that the psychopathology in individuals with intellectual disability (ID) has become an area of significant clinical and research interest. Individuals with ID are believed to be at a greater risk for co-occurring disorders compared to the typical population. By definition, ID involves deficits in adaptive behavior, which necessitates the use of community services, or specialized services at residential facilities to manage severe challenging behaviors or psychiatric disorders. The presence of co-occurring disorders in addition to ID can complicate treatment, limit available services, and restrict opportunities for individuals with ID. The present study examines the prevalence of co-occurring psychiatric disorders and ID in a sample of 78 individuals with mild to moderate ID living in a long-term residential treatment facility diagnosed with psychiatric disorders. Certain psychiatric disorders were more likely to co-occur together in this population. Identifying and treating individuals with multiple psychopathologies in addition to ID poses challenges unique to the population. ß 2014 Elsevier Ltd. All rights reserved.
Keywords: Intellectual disability Developmental disabilities Psychopathology Comorbidity Adults
In addition to cognitive and adaptive skill deficits (American Psychiatric Association, 2000; Luckasson et al., 2002), individuals with intellectual disability (ID) frequently exhibit symptoms of comorbid psychopathology (Bhaumik, Tyrer, McGrother, & Ganghadaran, 2008; Matson & Shoemaker, 2011; Matson & Smiroldo, 1997; Matson & Williams, 2014; Tonge & Einfeld, 2003; Werner & Stawski, 2012; White, Chant, Edwards, Townsend, & Waghorn, 2005). Estimates of the prevalence of co-occurring psychological disorders among individuals with ID vary widely (e.g., ranging from 7 to 97% across studies; Cooper, Smiley, Morrison, Williamson, & Allan, 2007; Matson, Smiroldo, Hamilton, & Baglio, 1997), partly due to methodological differences across analyses (Morgan, Leonard, Bourke, & Jablensky, 2008; Vereenooghe & Langdon, 2013). There is not a consensus among researchers regarding whether individuals with ID have greater psychopathology prevalence rates than the general population overall (Costello & Bouras, 2006; Morgan et al., 2008; Whitaker & Read, 2006), although there is evidence of this pattern for certain disorders (Deb, Thomas, & Bright, 2001; Dekker & Koot, 2003; Emerson, 2003). This pattern may also differ based on age of the individual and severity of cognitive deficit (Cherry, Matson, & Paclawskyj, 1997; Paclawskyj, Matson, Bamburg, & Baglio, 1997; Whitaker & Read, 2006). Regardless, recent recognition of the common
* Corresponding author at: Department of Psychology, Louisiana State University, Baton Rouge, LA 70803, United States. Tel.: +1 225 578 7792. E-mail address: [email protected] (N.C. Turygin). http://dx.doi.org/10.1016/j.ridd.2014.07.039 0891-4222/ß 2014 Elsevier Ltd. All rights reserved.
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occurrence of psychiatric problems among this population has led to an increased interest in research on this important topic (Hove & Havik, 2008; Kozlowski, Matson, Sipes, Hattier, & Bamburg, 2011; Matson et al., 1997a), especially due to the critical implications of the presence of comorbid psychopathology among individuals with ID (Horovitz, Shear, Mancini, & Pellerito, 2014; Turygin, Matson, & Adams, 2014). Although co-occurring psychopathologies among typically developing individuals is a frequent area of research, less research has been conducted regarding ID and multiple comorbid disorders, including the analysis of symptom clusters that may present among individuals in this population (Matson & Rivet, 2008). In contrast, co-occurring psychopathologies among typically developing individuals is a frequent topic of study. Researchers have observed a tendency for several disorders to frequently manifest concurrently in those without ID, including anxiety and mood disorders (Brown, Campbell, Lehman, Grisham, & Mancill, 2001; Cerda´, Sagdeo, & Galea, 2008; Erwin, Heimberg, Juster, & Mindlin, 2002; Kessler, Avenevoli, & Ries Merikangas, 2001), attention-deficit/hyperactivity disorder (ADHD) and conduct disorder or oppositional defiant disorder (Dunn & Kronenberger, 2012; Kessler et al., 2006), depression and substance abuse (Cerda´ et al., 2008; Grant et al., 2004), conduct disorder and substance use (Cerda´ et al., 2008), conduct disorder and schizophrenia (Hodgins, Tiihonen, & Ross, 2005; Regier et al., 1990; Swofford, Scheller-Gilkey, Miller, Woolwine, & Mance, 2000), autism and obsessivecompulsive disorder (Matson & Dempsey, 2009). Personality disorders are often comorbid with a wide variety of Axis I disorders (Lenzenweger, Lane, Loranger, & Kessler, 2007). As compared to typically developing individuals with a single psychiatric disorder, individuals with multiple psychiatric diagnoses often have more severe symptoms and worse prognoses (Angold, Costello, & Erkanli, 1999). Those with ID and autism have an especially high rate of comorbid psychopathology (Matson & LoVullo, 2009; Matson, LoVullo, Rivet, & Boisjoli, 2009). Similarly, evidence suggests that having multiple comorbid disorders in addition to ID appears to exacerbate existing problems with everyday functioning across multiple domains (Dekker & Koot, 2003; Matson et al., 1999; Smith & Matson, 2010). Furthermore, some researchers suggest that psychopathology is more impairing for children with ID than children without ID (Dekker & Koot, 2003). Thus, for individuals with ID, having multiple comorbid disorders may have even greater negative implications, including across wide ranging skills such as adaptive behavior (Matson, Dempsey, & Fodstad, 2009; Matson, Rivet, Fodstad, Dempsey, & Boisjoli, 2009). Although less common than research about single disorders comorbid with ID, a few studies have been conducted regarding symptom clusters exhibited by this population. For instance, Kozlowski and colleagues (2011) found significant correlations among pairs of disorders within a population with ID: organic and mood, mood and mania, and PDD/autism and stereotypies, although some overlapping items used to determine diagnoses in each pair likely played a role in the correlations. Additionally, Dekker and Koot (2003) found that 14.2% of children with ID in their sample had multiple disorders. Of the children in their sample who met criteria for ADHD, 44% also met criteria for ODD. The presence of co-occurring disorders in addition to ID can complicate treatment, limit available services, and restrict opportunities for individuals with ID. As of now, the similarities between patterns of multiple co-occurring disorders among typically developing individuals and persons with ID have yet to be determined. This study is an extension of a previous study of the prevalence of psychopathologies in adults with mild to moderate ID in a residential setting (Turygin et al., 2014). The purpose of the current study was to determine symptom clusters exhibited by a sample of adults with ID, to examine patterns of co-occurring psychopathologies in this sample. Some symptoms of multiple psychopathologies tend to occur together, with important clinical implications for assessment and treatment in this population. This issue will be explored in the present study. 1. Method 1.1. Participants The present study initially included 102 adults with an initial diagnosis of borderline, mild, or moderate ID, many with cooccurring medical and psychiatric disorders. Due to inability to ascertain the level of ID, three participants were excluded from the analyses, thus leaving a sample of 99 participants. Of these, 78 had a co-occurring diagnosis of a psychiatric disorder and were included in the present study. At the time of data collection, all participants were residing in either of two state-run developmental centers designed to treat individuals with a wide variety of intellectual and developmental disabilities. As in a preceding study (Turygin et al., 2014), diagnoses were recorded from the individual’s file and not diagnosed for the purposes of the present study. Intellectual disability status according to the DSM-IV-TR (APA, 2000) was determined at intake by an on-site licensed psychologist. Diagnoses incorporated information from a standardized measure of adaptive functioning (most frequently the Vineland Adaptive Behavior Scales, Second Edition; Sparrow, Cicchetti, & Balla, 2005) and administration of a standardized, individually administered IQ test (e.g., Stanford Binet). Reassessment of cognitive functioning occurred yearly thereafter. The licensed psychologist assigned diagnoses according to a consensus model after meeting with the individual, reviewing the individual’s file, and consulting with members of the individual’s interdisciplinary team. DSM-IV-TR criteria were used by licensed psychologists and psychiatrists working at the centers to assess co-occurring psychiatric disorders. These assessments were supplemented by administration of other measures as deemed appropriate by the psychologist. Inclusion criteria included a diagnosis of borderline, mild, or moderate ID. In this sample, 60.25% of participants (n = 47) were males and 39.74% (n = 31) were females, with no significant differences observed between sites, x2 (1, N = 78) = 0.50, p = .48,. Ages of participants ranged from 18 to 96 years (M = 38.39;
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SD = 20.28); significant differences [F(1, 71) = 12.09; p = .00] were found between sites with site 1 (N = 36) having greater variation in age (M = 34.13, SD = 19.57) than site 2 (N = 37; M = 31.91, SD = 11.68). Of this sample, 69.20% (n = 54) had mild ID, 26.90% (n = 21) had moderate ID, and 3.80% (n = 3) had borderline ID. Out of these, 60.30% (n = 47) were Caucasian, 38.5% (n = 30) were African American, and 1.30% (n = 1) was of another ethnic background. With regard to communication, 97.40% (n = 76) of individuals in our sample were able to communicate verbally, which was defined as the ability to at least verbally express one’s basic needs. Two participants (2.60%) were not able to communicate verbally. Twenty-three (29.48%) participants had a history of seizures, and 51 (65.38%) had no history of seizures, and seizure history information was not available for four participants. Demographic information is presented in Table 1. 1.2. Procedure Approval from the Institutional Review Board was obtained prior to onset of data collection for the present study and was conducted after approval by and in accordance with the policies of the Human Rights Committee at the residential facilities. Informed assent was obtained and witnessed by a staff member of the participant’s choice. Data used in the present study was gathered from pre-existing information in the individual’s treatment file and entered into a database, excluding any personally identifiable information. Types of disorders were then coded into categories, with psychiatric disorders divided into autism spectrum disorders (ASD); bipolar disorder; other mood disorders; schizophrenia and other psychotic disorders; impulse control disorder, oppositional defiant disorder (ODD), and conduct disorder (CD); schizoaffective disorder; substance use disorders; rule outs (undifferentiated); and other disorders. Combination of three disorders into the ‘‘impulse control disorder’’ category and a number of other disorders into the ‘‘other’’ group for coding purposes were based on relatively low frequency of these diagnoses in the sample. The ASD category included all DSM-IV-TR disorders in the ASD category (i.e., autism spectrum disorder, Asperger disorder, and Pervasive Developmental Disorder-Not Otherwise Specified [PDD-NOS]). Bipolar disorder included both Bipolar I and Bipolar II. Major depressive disorder, dysthymic disorder, and mood disorder NOS comprised the other mood disorder group. Schizophrenia and other psychotic disorders included schizophrenia, delusional disorder, and psychotic disorder NOS. The ‘‘other’’ category included eating disorders, narcolepsy, obsessive-compulsive disorder (OCD), paraphilias, sleep disorders, and other DSM-IV-TR Axis 1 disorders, each of which occurred at rates of no more than n = 4 in the present sample. 1.3. Statistical analyses Out of the entire sample, there were 78 participants with a psychiatric diagnosis in addition to ID. Twelve participants had an Axis II disorder but were not diagnosed with any Axis I disorder, and 22 had no diagnosis in addition to ID. Of the 78 participants with ID and at least one comorbid psychiatric diagnosis, 49 participants had a second psychiatric diagnosis. Data for Axis I diagnoses were reported in narrative form and coded into one of eight categories: ASD; bipolar disorder; other mood disorder; schizophrenia and psychotic disorders; impulse control, ODD and CD; schizoaffective disorder; and other disorders (which included eating disorders, OCD, anxiety disorders). Turygin et al. (2014) provide greater detail on the specific distribution of all ‘‘other’’ diagnoses in this sample. All analyses were conducted using SPSS version 18. The cluster analysis was conducted with all 78 participants included in the analysis. Dichotomous variables representing each diagnostic category were created and entered in the analysis. The eight diagnostic categories created by coding DSM-IV-TR diagnoses as stated above were determined by their total in the sample, such that each category had at least four occurrences in the sample. These categories were then chosen as the potential clusters for the analysis to investigate trends of co-occurring psychiatric diagnoses. The furthest neighbor linkage method of cluster analysis was used. In this method of analysis, each variable is first considered to be an independent cluster; next these items are sequentially combined into larger clusters by combining the most similar two clusters. The furthest Table 1 Demographic information for sample (N = 78).
Sex (percent) Male Female Race (percent) Caucasian African American Other Verbal (percent) Yes No Seizures (percent) Yes No
Mild
Moderate
Borderline
33 (42.31) 21 (26.92)
12 (15.38) 9 (11.55)
2 (2.56) 1 (1.28)
31 (39.74) 22 (28.20) 1 (1.28)
13 (16.67) 8 (10.27) 0 (0.00)
3 (3.84) 0 (0.00) 0 (0.00)
53 (67.94) 1 (1.28)
21 (26.92) 0 (0)
2 (2.56) 1 (1.28)
14 (17.94) 36 (46.18)
7 (8.97) 14 (17.94)
2 (2.56) 1 (1.28)
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neighbor linkage method tends to produce compact clusters which contain data points that are very similar (Kaufman & Rousseeuw, 2009). Russell and Rao distance parameter was used as a similarity measure; this parameter can be used with asymmetric dichotomous variables and marks the proportion of cases in which both observations share the trait of interest. The furthest neighbor linkage rule and the Russell and Rao distance parameter were chosen as we are searching for those clusters that correspond to participants who are most similar to one another with respect to the dichotomous variable of diagnosis. These particular parameters were chosen in order to increase the likelihood that those with the most similar diagnosis profile would be placed into the same cluster. 2. Results Eight clusters were evident within the remaining data based on a review of the resulting dendrogram. Follow up analysis revealed that Cluster 1 consisted of 13 participants with a personality disorder. Six of the participants in this cluster had only a personality disorder, and 7 had at least one co-occurring disorder. See Table 2 for all co-occurring disorders present within the cluster. Cluster 2 consisted of all participants with ASD (n = 8). Co-occurring disorders within this category were most commonly observed to be from the ‘‘other’’ category, while one had a co-occurring personality and ‘‘other’’ disorder. Cluster 3 consisted of participants who all had ‘‘other mood’’ disorders (n = 12). Within this group, 5 participants had an ‘‘other’’ disorder, 1 had a psychotic disorder, and 1 had a substance use disorder. Cluster 4 consisted solely of participants with bipolar disorder (n = 8). Co-occurring disorders in Cluster 4 included impulse, schizoaffective and ‘‘other.’’ All participants in Cluster 5 had schizophrenia or a psychotic disorder (n = 10), with a co-occurring ‘‘other’’ disorder, or co-occurring ‘‘other’’, impulse and substance use disorders. Cluster 6 consisted of 10 participants with schizoaffective disorders, 2 of whom had cooccurring other and substance use disorders, 2 with co-occurring substance use disorder, and 1 with impulse disorder. Cluster 7 consisted of participants with an ‘‘other’’ diagnosis (n = 10) with co-occurring substance and personality disorder (n = 2), or substance use disorder (n = 1), and schizophrenia or a psychotic disorder (n = 1). Cluster 8 consisted of participants (n = 7) diagnosed with substance use disorder with one with another from the other category. 3. Discussion The present study illustrates the disorders that commonly co-occur among adults with mild or moderate intellectual disability who reside in a residential treatment setting. These individuals represent those who are at present unable to reside in less-restrictive settings as a result of behavioral or medical problems. The successful management of co-occurring psychiatric disorders in this population may result in their ability to transition to less-restrictive settings and obtain a wider variety of personal and occupational opportunity. The analysis provided information on those co-occurring disorders that are likely to occur together in this population. For example, those with ASD only carried co-occurring disorders of a personality disorder, or diagnoses from the ‘‘other’’ category (enuresis/encopresis, PTSD, rule-out dementia, and Tourette’s). Those with other mood disorders were diagnosed with schizophrenia, ‘‘other’’ disorders, or substance use disorder. Schizophrenia or other psychotic disorders tended to co-occur with substance use, reflecting tendencies found in the general population (Hodgins et al., 2005; Regier et al., 1990; Swofford et al., 2000). The present study represents an initial step in understanding the relationships between psychiatric disorders as they occur in individuals with intellectual disability. The widest variety of co-occurring disorders occurred in those who were diagnosed with a personality disorder. Cooccurring disorders included bipolar disorder, impulse disorder, other mood disorders, schizoaffective disorder, and other disorders. This finding is unsurprising given the pervasive nature and complexity of personality disorders; furthermore, this result follows the trend found in the general population wherein personality disorders tend to co-occur with a wide variety of other psychiatric disorders (Lenzenweger et al., 2007). Bipolar disorder also tended to occur with impulse disorder, and ‘‘other’’ disorders. Impulse disorder occurred on its own more often than any other disorder, and also frequently co-occurred with a variety of other disorders, particularly bipolar disorder, schizoaffective, and personality disorders, indicating more heterogeneity of co-occurring disorders in individuals with impulse disorder. Table 2 Co-occurring disorders within each cluster. Cluster 1
Cluster 2
Cluster 3
Cluster 4
Personality (n = 13) Bipolar (n = 1) Other mood (n = 4) Impulse (n = 2) Schizoaffective (n = 1) Other (n = 1)
ASD (n = 8) Other (n = 4) Personality (n = 1)
Other mood (n = 12) Schizophrenia/Psychotic (n = 1) Other (n = 5) Substance (n = 1)
Bipolar (n = 8) Impulse (n = 3) Schizoaffective (n = 1) Other (n = 3)
Cluster 5
Cluster 6
Cluster 7
Cluster 8
Schizophrenia/Psychotic (n = 10) Impulse (n = 1) Substance (n = 4) Other (n = 2)
Schizoaffective (n = 10) Substance (n = 4) Other (n = 2) Impulse (n = 1)
Other (n = 10) Personality (n = 2) Schizophrenia/Psychotic (n = 1) Substance (n = 3)
Impulse (n = 7) Other (n = 1)
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One major limitation of the present study resulted from the low frequency of certain disorders within the sample, which were placed within the ‘‘other’’ category and included disorders such as anxiety disorders, obsessive-compulsive disorder, and pica. This limited the results of the present study to the focus of the relationships between those disorders which made up a large enough portion of the sample to be included within the study. The absence of discrete groups of these disorders was a reflection of the population at the two centers from which we obtained data, in which the disorders were observed at low rates. This information would be useful, and further studies should continue to explore the relationship between the disorders observed in the present study along with the disorders omitted from the present study. Future studies may also wish to cluster with respect to age groups, race, or gender, particularly as more is known about gender differences in disorders in ID. Gender information would be particularly useful when examining co-occurring disorders such as ASD that are known to be present more frequently in males (Rivet & Matson, 2011). The relative low frequency of ‘‘other’’ disorders in the present study poses additional questions. Given the fact that a sample of individuals residing at a residential treatment facility is inherently a sample with greater needs than a community sample, individuals with ID in these residential settings may be more likely than a community sample to be diagnosed with disorders perceived to be more ‘‘severe,’’ such as psychotic disorder and schizoaffective disorders. It is unsurprising that a residential facility would represent a setting in which higher numbers of these ‘‘severe’’ disorders are observed. Diagnostic overshadowing is an alternate explanation, as symptoms of co-occurring disorders from the ‘‘other’’ category (e.g., anxiety, OCD) may be assumed to relate to the intellectual disability or ‘‘more severe’’ psychiatric condition and thus not warrant a separate diagnosis. Mental health and training needs of individuals residing in these settings are complicated by cooccurring medical, psychosocial, and economic conditions, all of which pose further diagnostic challenges. Overall, however, it appears that individuals dually diagnosed with ID and psychopathology have a high likelihood of not only one, but multiple psychiatric diagnoses. This co-occurrence is unsurprising given the frequency of concomitant psychiatric disorders in the general population. These results highlight the need for thorough assessment of the psychological needs and individualized treatment plans for dually diagnosed individuals. Given the high use of psychotropic drug use and the potential side effects that occur, this data should result in more precise and thus safer treatment (Advokat, Mayville, & Matson, 2000; Matson et al., 1998; Matson & Wilkins, 2008; Singh, Matson, Cooper, Dixon, & Sturmey, 2005). Additionally, a host of psychological methods are also applicable for treatment (Matson, Mahan, & LoVullo, 2009). Better understanding of the nature of these overlapping disorders, then, should result in more precise and complimentary treatment approaches.
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Contents lists available at ScienceDirect
Research in Developmental Disabilities
Co-occurring disorder clusters in adults with mild and moderate intellectual disability in residential treatment settings Nicole C. Turygin *, Johnny L. Matson, Hilary L. Adams, Lindsey W. Williams Louisiana State University, United States
A R T I C L E I N F O
A B S T R A C T
Article history: Received 8 April 2014 Received in revised form 8 July 2014 Accepted 20 July 2014 Available online
In the typically developing population, co-occurring psychopathology is not uncommon and is a topic of importance among psychologists. It is only recently that the psychopathology in individuals with intellectual disability (ID) has become an area of significant clinical and research interest. Individuals with ID are believed to be at a greater risk for co-occurring disorders compared to the typical population. By definition, ID involves deficits in adaptive behavior, which necessitates the use of community services, or specialized services at residential facilities to manage severe challenging behaviors or psychiatric disorders. The presence of co-occurring disorders in addition to ID can complicate treatment, limit available services, and restrict opportunities for individuals with ID. The present study examines the prevalence of co-occurring psychiatric disorders and ID in a sample of 78 individuals with mild to moderate ID living in a long-term residential treatment facility diagnosed with psychiatric disorders. Certain psychiatric disorders were more likely to co-occur together in this population. Identifying and treating individuals with multiple psychopathologies in addition to ID poses challenges unique to the population. ß 2014 Elsevier Ltd. All rights reserved.
Keywords: Intellectual disability Developmental disabilities Psychopathology Comorbidity Adults
In addition to cognitive and adaptive skill deficits (American Psychiatric Association, 2000; Luckasson et al., 2002), individuals with intellectual disability (ID) frequently exhibit symptoms of comorbid psychopathology (Bhaumik, Tyrer, McGrother, & Ganghadaran, 2008; Matson & Shoemaker, 2011; Matson & Smiroldo, 1997; Matson & Williams, 2014; Tonge & Einfeld, 2003; Werner & Stawski, 2012; White, Chant, Edwards, Townsend, & Waghorn, 2005). Estimates of the prevalence of co-occurring psychological disorders among individuals with ID vary widely (e.g., ranging from 7 to 97% across studies; Cooper, Smiley, Morrison, Williamson, & Allan, 2007; Matson, Smiroldo, Hamilton, & Baglio, 1997), partly due to methodological differences across analyses (Morgan, Leonard, Bourke, & Jablensky, 2008; Vereenooghe & Langdon, 2013). There is not a consensus among researchers regarding whether individuals with ID have greater psychopathology prevalence rates than the general population overall (Costello & Bouras, 2006; Morgan et al., 2008; Whitaker & Read, 2006), although there is evidence of this pattern for certain disorders (Deb, Thomas, & Bright, 2001; Dekker & Koot, 2003; Emerson, 2003). This pattern may also differ based on age of the individual and severity of cognitive deficit (Cherry, Matson, & Paclawskyj, 1997; Paclawskyj, Matson, Bamburg, & Baglio, 1997; Whitaker & Read, 2006). Regardless, recent recognition of the common
* Corresponding author at: Department of Psychology, Louisiana State University, Baton Rouge, LA 70803, United States. Tel.: +1 225 578 7792. E-mail address: [email protected] (N.C. Turygin). http://dx.doi.org/10.1016/j.ridd.2014.07.039 0891-4222/ß 2014 Elsevier Ltd. All rights reserved.
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occurrence of psychiatric problems among this population has led to an increased interest in research on this important topic (Hove & Havik, 2008; Kozlowski, Matson, Sipes, Hattier, & Bamburg, 2011; Matson et al., 1997a), especially due to the critical implications of the presence of comorbid psychopathology among individuals with ID (Horovitz, Shear, Mancini, & Pellerito, 2014; Turygin, Matson, & Adams, 2014). Although co-occurring psychopathologies among typically developing individuals is a frequent area of research, less research has been conducted regarding ID and multiple comorbid disorders, including the analysis of symptom clusters that may present among individuals in this population (Matson & Rivet, 2008). In contrast, co-occurring psychopathologies among typically developing individuals is a frequent topic of study. Researchers have observed a tendency for several disorders to frequently manifest concurrently in those without ID, including anxiety and mood disorders (Brown, Campbell, Lehman, Grisham, & Mancill, 2001; Cerda´, Sagdeo, & Galea, 2008; Erwin, Heimberg, Juster, & Mindlin, 2002; Kessler, Avenevoli, & Ries Merikangas, 2001), attention-deficit/hyperactivity disorder (ADHD) and conduct disorder or oppositional defiant disorder (Dunn & Kronenberger, 2012; Kessler et al., 2006), depression and substance abuse (Cerda´ et al., 2008; Grant et al., 2004), conduct disorder and substance use (Cerda´ et al., 2008), conduct disorder and schizophrenia (Hodgins, Tiihonen, & Ross, 2005; Regier et al., 1990; Swofford, Scheller-Gilkey, Miller, Woolwine, & Mance, 2000), autism and obsessivecompulsive disorder (Matson & Dempsey, 2009). Personality disorders are often comorbid with a wide variety of Axis I disorders (Lenzenweger, Lane, Loranger, & Kessler, 2007). As compared to typically developing individuals with a single psychiatric disorder, individuals with multiple psychiatric diagnoses often have more severe symptoms and worse prognoses (Angold, Costello, & Erkanli, 1999). Those with ID and autism have an especially high rate of comorbid psychopathology (Matson & LoVullo, 2009; Matson, LoVullo, Rivet, & Boisjoli, 2009). Similarly, evidence suggests that having multiple comorbid disorders in addition to ID appears to exacerbate existing problems with everyday functioning across multiple domains (Dekker & Koot, 2003; Matson et al., 1999; Smith & Matson, 2010). Furthermore, some researchers suggest that psychopathology is more impairing for children with ID than children without ID (Dekker & Koot, 2003). Thus, for individuals with ID, having multiple comorbid disorders may have even greater negative implications, including across wide ranging skills such as adaptive behavior (Matson, Dempsey, & Fodstad, 2009; Matson, Rivet, Fodstad, Dempsey, & Boisjoli, 2009). Although less common than research about single disorders comorbid with ID, a few studies have been conducted regarding symptom clusters exhibited by this population. For instance, Kozlowski and colleagues (2011) found significant correlations among pairs of disorders within a population with ID: organic and mood, mood and mania, and PDD/autism and stereotypies, although some overlapping items used to determine diagnoses in each pair likely played a role in the correlations. Additionally, Dekker and Koot (2003) found that 14.2% of children with ID in their sample had multiple disorders. Of the children in their sample who met criteria for ADHD, 44% also met criteria for ODD. The presence of co-occurring disorders in addition to ID can complicate treatment, limit available services, and restrict opportunities for individuals with ID. As of now, the similarities between patterns of multiple co-occurring disorders among typically developing individuals and persons with ID have yet to be determined. This study is an extension of a previous study of the prevalence of psychopathologies in adults with mild to moderate ID in a residential setting (Turygin et al., 2014). The purpose of the current study was to determine symptom clusters exhibited by a sample of adults with ID, to examine patterns of co-occurring psychopathologies in this sample. Some symptoms of multiple psychopathologies tend to occur together, with important clinical implications for assessment and treatment in this population. This issue will be explored in the present study. 1. Method 1.1. Participants The present study initially included 102 adults with an initial diagnosis of borderline, mild, or moderate ID, many with cooccurring medical and psychiatric disorders. Due to inability to ascertain the level of ID, three participants were excluded from the analyses, thus leaving a sample of 99 participants. Of these, 78 had a co-occurring diagnosis of a psychiatric disorder and were included in the present study. At the time of data collection, all participants were residing in either of two state-run developmental centers designed to treat individuals with a wide variety of intellectual and developmental disabilities. As in a preceding study (Turygin et al., 2014), diagnoses were recorded from the individual’s file and not diagnosed for the purposes of the present study. Intellectual disability status according to the DSM-IV-TR (APA, 2000) was determined at intake by an on-site licensed psychologist. Diagnoses incorporated information from a standardized measure of adaptive functioning (most frequently the Vineland Adaptive Behavior Scales, Second Edition; Sparrow, Cicchetti, & Balla, 2005) and administration of a standardized, individually administered IQ test (e.g., Stanford Binet). Reassessment of cognitive functioning occurred yearly thereafter. The licensed psychologist assigned diagnoses according to a consensus model after meeting with the individual, reviewing the individual’s file, and consulting with members of the individual’s interdisciplinary team. DSM-IV-TR criteria were used by licensed psychologists and psychiatrists working at the centers to assess co-occurring psychiatric disorders. These assessments were supplemented by administration of other measures as deemed appropriate by the psychologist. Inclusion criteria included a diagnosis of borderline, mild, or moderate ID. In this sample, 60.25% of participants (n = 47) were males and 39.74% (n = 31) were females, with no significant differences observed between sites, x2 (1, N = 78) = 0.50, p = .48,. Ages of participants ranged from 18 to 96 years (M = 38.39;
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SD = 20.28); significant differences [F(1, 71) = 12.09; p = .00] were found between sites with site 1 (N = 36) having greater variation in age (M = 34.13, SD = 19.57) than site 2 (N = 37; M = 31.91, SD = 11.68). Of this sample, 69.20% (n = 54) had mild ID, 26.90% (n = 21) had moderate ID, and 3.80% (n = 3) had borderline ID. Out of these, 60.30% (n = 47) were Caucasian, 38.5% (n = 30) were African American, and 1.30% (n = 1) was of another ethnic background. With regard to communication, 97.40% (n = 76) of individuals in our sample were able to communicate verbally, which was defined as the ability to at least verbally express one’s basic needs. Two participants (2.60%) were not able to communicate verbally. Twenty-three (29.48%) participants had a history of seizures, and 51 (65.38%) had no history of seizures, and seizure history information was not available for four participants. Demographic information is presented in Table 1. 1.2. Procedure Approval from the Institutional Review Board was obtained prior to onset of data collection for the present study and was conducted after approval by and in accordance with the policies of the Human Rights Committee at the residential facilities. Informed assent was obtained and witnessed by a staff member of the participant’s choice. Data used in the present study was gathered from pre-existing information in the individual’s treatment file and entered into a database, excluding any personally identifiable information. Types of disorders were then coded into categories, with psychiatric disorders divided into autism spectrum disorders (ASD); bipolar disorder; other mood disorders; schizophrenia and other psychotic disorders; impulse control disorder, oppositional defiant disorder (ODD), and conduct disorder (CD); schizoaffective disorder; substance use disorders; rule outs (undifferentiated); and other disorders. Combination of three disorders into the ‘‘impulse control disorder’’ category and a number of other disorders into the ‘‘other’’ group for coding purposes were based on relatively low frequency of these diagnoses in the sample. The ASD category included all DSM-IV-TR disorders in the ASD category (i.e., autism spectrum disorder, Asperger disorder, and Pervasive Developmental Disorder-Not Otherwise Specified [PDD-NOS]). Bipolar disorder included both Bipolar I and Bipolar II. Major depressive disorder, dysthymic disorder, and mood disorder NOS comprised the other mood disorder group. Schizophrenia and other psychotic disorders included schizophrenia, delusional disorder, and psychotic disorder NOS. The ‘‘other’’ category included eating disorders, narcolepsy, obsessive-compulsive disorder (OCD), paraphilias, sleep disorders, and other DSM-IV-TR Axis 1 disorders, each of which occurred at rates of no more than n = 4 in the present sample. 1.3. Statistical analyses Out of the entire sample, there were 78 participants with a psychiatric diagnosis in addition to ID. Twelve participants had an Axis II disorder but were not diagnosed with any Axis I disorder, and 22 had no diagnosis in addition to ID. Of the 78 participants with ID and at least one comorbid psychiatric diagnosis, 49 participants had a second psychiatric diagnosis. Data for Axis I diagnoses were reported in narrative form and coded into one of eight categories: ASD; bipolar disorder; other mood disorder; schizophrenia and psychotic disorders; impulse control, ODD and CD; schizoaffective disorder; and other disorders (which included eating disorders, OCD, anxiety disorders). Turygin et al. (2014) provide greater detail on the specific distribution of all ‘‘other’’ diagnoses in this sample. All analyses were conducted using SPSS version 18. The cluster analysis was conducted with all 78 participants included in the analysis. Dichotomous variables representing each diagnostic category were created and entered in the analysis. The eight diagnostic categories created by coding DSM-IV-TR diagnoses as stated above were determined by their total in the sample, such that each category had at least four occurrences in the sample. These categories were then chosen as the potential clusters for the analysis to investigate trends of co-occurring psychiatric diagnoses. The furthest neighbor linkage method of cluster analysis was used. In this method of analysis, each variable is first considered to be an independent cluster; next these items are sequentially combined into larger clusters by combining the most similar two clusters. The furthest Table 1 Demographic information for sample (N = 78).
Sex (percent) Male Female Race (percent) Caucasian African American Other Verbal (percent) Yes No Seizures (percent) Yes No
Mild
Moderate
Borderline
33 (42.31) 21 (26.92)
12 (15.38) 9 (11.55)
2 (2.56) 1 (1.28)
31 (39.74) 22 (28.20) 1 (1.28)
13 (16.67) 8 (10.27) 0 (0.00)
3 (3.84) 0 (0.00) 0 (0.00)
53 (67.94) 1 (1.28)
21 (26.92) 0 (0)
2 (2.56) 1 (1.28)
14 (17.94) 36 (46.18)
7 (8.97) 14 (17.94)
2 (2.56) 1 (1.28)
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neighbor linkage method tends to produce compact clusters which contain data points that are very similar (Kaufman & Rousseeuw, 2009). Russell and Rao distance parameter was used as a similarity measure; this parameter can be used with asymmetric dichotomous variables and marks the proportion of cases in which both observations share the trait of interest. The furthest neighbor linkage rule and the Russell and Rao distance parameter were chosen as we are searching for those clusters that correspond to participants who are most similar to one another with respect to the dichotomous variable of diagnosis. These particular parameters were chosen in order to increase the likelihood that those with the most similar diagnosis profile would be placed into the same cluster. 2. Results Eight clusters were evident within the remaining data based on a review of the resulting dendrogram. Follow up analysis revealed that Cluster 1 consisted of 13 participants with a personality disorder. Six of the participants in this cluster had only a personality disorder, and 7 had at least one co-occurring disorder. See Table 2 for all co-occurring disorders present within the cluster. Cluster 2 consisted of all participants with ASD (n = 8). Co-occurring disorders within this category were most commonly observed to be from the ‘‘other’’ category, while one had a co-occurring personality and ‘‘other’’ disorder. Cluster 3 consisted of participants who all had ‘‘other mood’’ disorders (n = 12). Within this group, 5 participants had an ‘‘other’’ disorder, 1 had a psychotic disorder, and 1 had a substance use disorder. Cluster 4 consisted solely of participants with bipolar disorder (n = 8). Co-occurring disorders in Cluster 4 included impulse, schizoaffective and ‘‘other.’’ All participants in Cluster 5 had schizophrenia or a psychotic disorder (n = 10), with a co-occurring ‘‘other’’ disorder, or co-occurring ‘‘other’’, impulse and substance use disorders. Cluster 6 consisted of 10 participants with schizoaffective disorders, 2 of whom had cooccurring other and substance use disorders, 2 with co-occurring substance use disorder, and 1 with impulse disorder. Cluster 7 consisted of participants with an ‘‘other’’ diagnosis (n = 10) with co-occurring substance and personality disorder (n = 2), or substance use disorder (n = 1), and schizophrenia or a psychotic disorder (n = 1). Cluster 8 consisted of participants (n = 7) diagnosed with substance use disorder with one with another from the other category. 3. Discussion The present study illustrates the disorders that commonly co-occur among adults with mild or moderate intellectual disability who reside in a residential treatment setting. These individuals represent those who are at present unable to reside in less-restrictive settings as a result of behavioral or medical problems. The successful management of co-occurring psychiatric disorders in this population may result in their ability to transition to less-restrictive settings and obtain a wider variety of personal and occupational opportunity. The analysis provided information on those co-occurring disorders that are likely to occur together in this population. For example, those with ASD only carried co-occurring disorders of a personality disorder, or diagnoses from the ‘‘other’’ category (enuresis/encopresis, PTSD, rule-out dementia, and Tourette’s). Those with other mood disorders were diagnosed with schizophrenia, ‘‘other’’ disorders, or substance use disorder. Schizophrenia or other psychotic disorders tended to co-occur with substance use, reflecting tendencies found in the general population (Hodgins et al., 2005; Regier et al., 1990; Swofford et al., 2000). The present study represents an initial step in understanding the relationships between psychiatric disorders as they occur in individuals with intellectual disability. The widest variety of co-occurring disorders occurred in those who were diagnosed with a personality disorder. Cooccurring disorders included bipolar disorder, impulse disorder, other mood disorders, schizoaffective disorder, and other disorders. This finding is unsurprising given the pervasive nature and complexity of personality disorders; furthermore, this result follows the trend found in the general population wherein personality disorders tend to co-occur with a wide variety of other psychiatric disorders (Lenzenweger et al., 2007). Bipolar disorder also tended to occur with impulse disorder, and ‘‘other’’ disorders. Impulse disorder occurred on its own more often than any other disorder, and also frequently co-occurred with a variety of other disorders, particularly bipolar disorder, schizoaffective, and personality disorders, indicating more heterogeneity of co-occurring disorders in individuals with impulse disorder. Table 2 Co-occurring disorders within each cluster. Cluster 1
Cluster 2
Cluster 3
Cluster 4
Personality (n = 13) Bipolar (n = 1) Other mood (n = 4) Impulse (n = 2) Schizoaffective (n = 1) Other (n = 1)
ASD (n = 8) Other (n = 4) Personality (n = 1)
Other mood (n = 12) Schizophrenia/Psychotic (n = 1) Other (n = 5) Substance (n = 1)
Bipolar (n = 8) Impulse (n = 3) Schizoaffective (n = 1) Other (n = 3)
Cluster 5
Cluster 6
Cluster 7
Cluster 8
Schizophrenia/Psychotic (n = 10) Impulse (n = 1) Substance (n = 4) Other (n = 2)
Schizoaffective (n = 10) Substance (n = 4) Other (n = 2) Impulse (n = 1)
Other (n = 10) Personality (n = 2) Schizophrenia/Psychotic (n = 1) Substance (n = 3)
Impulse (n = 7) Other (n = 1)
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One major limitation of the present study resulted from the low frequency of certain disorders within the sample, which were placed within the ‘‘other’’ category and included disorders such as anxiety disorders, obsessive-compulsive disorder, and pica. This limited the results of the present study to the focus of the relationships between those disorders which made up a large enough portion of the sample to be included within the study. The absence of discrete groups of these disorders was a reflection of the population at the two centers from which we obtained data, in which the disorders were observed at low rates. This information would be useful, and further studies should continue to explore the relationship between the disorders observed in the present study along with the disorders omitted from the present study. Future studies may also wish to cluster with respect to age groups, race, or gender, particularly as more is known about gender differences in disorders in ID. Gender information would be particularly useful when examining co-occurring disorders such as ASD that are known to be present more frequently in males (Rivet & Matson, 2011). The relative low frequency of ‘‘other’’ disorders in the present study poses additional questions. Given the fact that a sample of individuals residing at a residential treatment facility is inherently a sample with greater needs than a community sample, individuals with ID in these residential settings may be more likely than a community sample to be diagnosed with disorders perceived to be more ‘‘severe,’’ such as psychotic disorder and schizoaffective disorders. It is unsurprising that a residential facility would represent a setting in which higher numbers of these ‘‘severe’’ disorders are observed. Diagnostic overshadowing is an alternate explanation, as symptoms of co-occurring disorders from the ‘‘other’’ category (e.g., anxiety, OCD) may be assumed to relate to the intellectual disability or ‘‘more severe’’ psychiatric condition and thus not warrant a separate diagnosis. Mental health and training needs of individuals residing in these settings are complicated by cooccurring medical, psychosocial, and economic conditions, all of which pose further diagnostic challenges. Overall, however, it appears that individuals dually diagnosed with ID and psychopathology have a high likelihood of not only one, but multiple psychiatric diagnoses. This co-occurrence is unsurprising given the frequency of concomitant psychiatric disorders in the general population. These results highlight the need for thorough assessment of the psychological needs and individualized treatment plans for dually diagnosed individuals. Given the high use of psychotropic drug use and the potential side effects that occur, this data should result in more precise and thus safer treatment (Advokat, Mayville, & Matson, 2000; Matson et al., 1998; Matson & Wilkins, 2008; Singh, Matson, Cooper, Dixon, & Sturmey, 2005). Additionally, a host of psychological methods are also applicable for treatment (Matson, Mahan, & LoVullo, 2009). Better understanding of the nature of these overlapping disorders, then, should result in more precise and complimentary treatment approaches.
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