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The relationship between psychopathology symptom clusters and the presence of comorbid psychopathology in individuals with severe to profound intellectual disability
Research in Developmental Disabilities 32 (2011) 1610–1614
Contents lists available at ScienceDirect
Research in Developmental Disabilities
The relationship between psychopathology symptom clusters and the presence of comorbid psychopathology in individuals with severe to profound intellectual disability Alison M. Kozlowski a, Johnny L. Matson a,*, Megan Sipes a, Megan A. Hattier a, Jay W. Bamburg b a b
Department of Psychology, Louisiana State University, Baton Rouge, LA 70803, United States Pinecrest Supports and Services Center, Pineville, LA, United States
A R T I C L E I N F O
A B S T R A C T
Article history: Received 18 December 2010 Accepted 19 January 2011 Available online 4 March 2011
In the typically developing population, comorbid psychopathology refers to the cooccurrence of two different psychopathologies other than cognitive impairments. With respect to individuals with intellectual disability, comorbidity is often described as cognitive deficits and one additional psychopathology manifesting together. However, just as within the typically developing population, individuals with intellectual disability may also present with symptoms of two or more additional disorders. The presentation of these symptom clusters may similarly correlate. Therefore, the current study used the Diagnostic Assessment for the Severely Handicapped—II in order to examine relationships between psychopathological symptom clusters in adults with severe to profound intellectual disability. Additionally, we assessed comorbid presentation of disorders other than cognitive impairments in these same adults. Several symptom clusters were identified as being related with moderate to strong positive correlations. Furthermore, elevations on the Impulse subscale were noted to be the most prevalent in the current sample, with comorbid elevations most commonly occurring along the Mood, Mania, and Anxiety subscales. The significance of these findings is discussed. ß 2011 Elsevier Ltd. All rights reserved.
Keywords: Intellectual disability Mental retardation Comorbid psychopathology DASH-II
1. Introduction Individuals with intellectual disabilities (IDs) experience cognitive deficits as well as impairments in adaptive and social skills (Ashworth, Hirdes, & Martin, 2009; Soenen, VanBerckelaer-Onnes, & Scholte, 2009). In addition, challenging behaviors such as physical aggression, self-injurious behavior, and pica are fairly common in those with ID (Duncan, Matson, Bamburg, Cherry, & Buckley, 1999; Emerson et al., 2001). In many cases, aside from these challenging behaviors, individuals with ID also exhibit symptoms of comorbid psychopathology (Duncan et al., 1999; McCarthy et al., 2010; Smith & Matson, 2010; Sturmey, Laud, Cooper, Matson, & Fodstad, 2010a, 2010b). Estimates suggest that up to 4–40% of those with ID exhibit comorbidity which makes the topic an important area to investigate (Deb, Thomas, & Bright, 2001; Dekker & Koot, 2003; Rojahn, Borthwick-Duffy, Jacobson, 1993). In those with ID, some of the commonly seen mental health disorders include depression, attention-deficit/hyperactivity disorder, and anxiety disorders, among others (Deb et al., 2001; Dekker & Koot, 2003; Hastings, Beck, Daley, & Hill, 2005).
* Corresponding author. E-mail address: [email protected] (J.L. Matson). 0891-4222/$ – see front matter ß 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.ridd.2011.02.004
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While researchers have begun to explore comorbid diagnoses in people with ID, the definition of comorbidity is often in reference to the presence of ID along with one other form of psychopathology (Fidler & Jameson, 2008; LoVullo & Matson, 2009). For example, autism spectrum disorders (ASDs) and ID are commonly researched as the two have high rates of comorbidity (LoVullo & Matson, 2009; Matson & Nebel-Schwalm, 2007; Matson & Shoemaker, 2009). However, researchers have not yet investigated thoroughly the relationships between two different forms of psychopathology in addition to ID. This type of research is seen commonly in the typically developing population. For instance, a large body of literature examines the interaction between mood and anxiety disorders in those with normal cognitive functioning (Erwin, Heimberg, Juster, & Mindlin, 2002; Naragon-Gainey, 2010; Olatunji, Cisler, & Tolin, 2010). The interactions of other symptom classes have also been supported in the literature, such as substance use disorders and anxiety disorders (Grant et al., 2004), psychotic disorders and mood disorders (Armando et al., 2010), and mood disorders and conduct disorder (Kovacs, Paulauskas, Gatsonis, & Richards, 1988). Evidence supports the presence of one disorder or class of symptoms will affect the likelihood of other disorders and symptoms. As mentioned above, while the literature examining the influence of different types of comorbid symptoms is strong, this research using samples with ID is lacking. For example, it is unknown if elevations in one symptom category are likely to result in elevations of other symptoms related to a different type of psychopathology. However, some research has shown that in general, the presence of two or more disorders in addition to ID resulted in greater impairments in daily functioning (Dekker & Koot, 2003), which suggests that the interactions between symptom clusters is important. Therefore, the purpose of the current study was to examine the relationship between different symptoms of psychopathology in those with ID as well as the possibility of comorbid psychopathology in these individuals as defined in the typically developing population. 2. Method 2.1. Participants Seventy-six residents of a state-run developmental center in Louisiana served as the sample for this study. Participants ranged in age from 20 to 89 years with a mean age of 52.66 years (SD = 14.98). Since the DASH-II, which is described below, is designed for both individuals with severe and profound intellectual disability, all participants included in this study had prior diagnoses of either of these two. In regard to gender, 55.3% of the sample was male. The ethnicity of the participants was recorded as Caucasian (69.7%), African American (23.7%), or Unidentified (6.6%). 2.2. Measure The Diagnostic Assessment for the Severely Handicapped—II (DASH-II): The DASH-II is an informant-based assessment which screens psychopathological symptoms in individuals with severe to profound intellectual disability (Matson, 1995). The 84 questions which make up the DASH-II are divided into the following 13 subscales: Anxiety, Depression, Mania, PDD/Autism, Schizophrenia, Stereotypies/Tics, Self-Injurious Behavior, Elimination Disorders, Eating Disorders, Sleep Disorders, Sexual Disorders, Organic Problems, and Impulse Control and Miscellaneous Behavior Problems. This broad-based instrument measures the frequency, duration, and severity of these symptoms on a 0–2 scale. With respect to these indices, a 0 indicates no occurrence, less than 1 month, and no disruption or damages, respectively. A score of 1 corresponds to a frequency between 1 and 10 times, duration of 1–12 months, and a behavior that has not caused damage but has interrupted the activities of others. Meanwhile, a score of 2 along each index indicates an occurrence over 10 times, duration over 12 months, and causing injury or property damage, respectively. Interrater reliability of the DASH-II has been well established with percent agreement estimates for the frequency, duration, and severity dimensions as .86, .85, and .95, respectively (Sevin, Matson, Williams, & Kirkpatrick-Sanchez, 1995). In regard to test–retest reliability, percent agreement estimates across all items was .84 for both frequency and duration and .91 for severity. Validity for some individual subscales has also been established including the Mania (Matson & Smiroldo, 1997), Autism/PDD (Matson, Smiroldo, & Hastings, 1997), and Schizophrenia (Bamburg, Cherry, Matson, & Penn, 2001) subscales. For eight of the subscales (i.e., Impulse, Organic, Anxiety, Mood, Mania, Autism/PDD, Schizophrenia, and Stereotypies), cutoff scores have been indicated as those receiving a total frequency score at least one standard deviation above the mean (Matson & Smiroldo, 1997). For the remaining five subscales, severity scores are used to determine cutoffs. 2.3. Procedure Employees with at least a master’s level degree in psychology administered the DASH-II by clinical interview with a direct care staff familiar with the individual and knowledgeable of their behaviors. In order for the direct care staff to be qualified to serve as the informant, they must have known and worked with the individual being assessed for at least six months. The interviewer read the instructions, each item of the DASH-II, and possible response choices to the informant. 2.4. Statistical analysis For the current study, only the eight aforementioned subscales for which there have been statistically defined cutoff criteria were included (i.e., Impulse, Organic, Anxiety, Mood, Mania, PDD/Autism, Schizophrenia, and Stereotypies).
A.M. Kozlowski et al. / Research in Developmental Disabilities 32 (2011) 1610–1614
1612 Table 1 Multiple bivariate correlations. Impulse Organic Pearson’s r p-value Anxiety Pearson’s r p-value Mood Pearson’s r p-value Mania Pearson’s r p-value PDD Pearson’s r p-value Schizophrenia Pearson’s r p-value Stereotypies Pearson’s r p-value *
Organic
Anxiety
Mood
Mania
PDD
Schizophrenia
.236 .040 .400 .000*
.242 .035
.330 .004
.735 .000*
.259 .024
.307 .007
.895 .000*
.258 .025
.697 .000*
.438 .000*
.218 .059
.145 .211
.186 .108
.240 .037
.256 .025
.379 .001*
.180 .119
.444 .000*
.381 .001*
.027 .814
.296 .009
.126 .280
.071 .540
.091 .432
.146 .208
.812 .000*
.064 .581
Clinically significant at .001 level.
Additionally, due to the small number of items on each subscale, participants missing any data were excluded from the analyses. Furthermore, inclusion criteria required the participant to have met cutoff on at least one of the eight subscales. This criterion was put in place to avoid significant correlations being noted due to zero or near-zero endorsements of all behaviors on the DASH-II. In order to determine whether or not there were relationships between comorbid psychopathology elevations on the DASH-II, two-tailed multiple bivariate correlations were computed with each subscale entered as the variables. To control for inflation of Type I error, a significance level of .05 divided by the number of simultaneous tests (n = 28) was chosen. Therefore, a significance level of .001 was used for all correlations. Next, concurrent frequency of clinically significant elevations on DASH-II subscales was explored to identify which clusters of psychopathology most commonly occurred together. 3. Results Of the 28 correlations analyzed, eight were found to be clinically significant. Symptom endorsements on the Impulse subscale were significantly positively correlated with elevations on the Anxiety (r = .400, p = .000) and PDD/Autism (r = .438, p = .000) subscales. Elevations on the Schizophrenia subscale were positively significantly correlated with those on the Organic (r = .379, p = .001), Mood (r = .444, p = .000), and Mania (r = .381, p = .001) subscales. Additionally, symptom endorsements on the Organic subscale were significantly positively correlated with elevations on the Mood subscale (r = .735, p = .000), those on the Mood subscale were significantly positively correlated with elevations on the Mania subscale (r = .697, p = .000), and elevations on the PDD/Autism subscale were significantly positively correlated with endorsements on the Stereotypies subscale (r = .812, p = .000). Please see Table 1 for a breakdown of correlation coefficients and associated significance levels for all correlations assessed. Next, a frequency count of all clinically significant subscale elevations on the DASH-II was compiled to identify those subscales which commonly co-occurred. Those individuals demonstrating only one clinically significant elevation on the DASHII comprised 38.2% of the total sample. The remaining 61.8% of the sample had clinically significant elevations on two or more subscales of the DASH-II. The most common clinically significant elevations were on the Impulse subscale (51.3%), followed by the Mania (40.8%) and Mood (39.5%) subscales. Individuals with two or three concurrent clinical elevations comprised 35.5% of the total sample and were investigated further with respect to the most common co-occurring clinically significant elevations. All participants with more than three clinically significant elevations were excluded because it was believed that these individuals displayed complex diagnostic pictures that did not demonstrate clear patterns with regard to comorbid psychopathologies. Of those individuals with two or three clinical elevations, 62.96% had elevations along the Impulse subscale. These individuals most commonly had concurrent elevations on the Anxiety, Mood, and/or Mania subscales. 4. Discussion The aim of the current study was to address the possibility of co-occurring psychopathological disorders within the ID population. Although ID co-occurring with another disorder is considered to be a comorbid diagnosis in and of itself (Duncan et al., 1999; McCarthy et al., 2010), comorbidity within the typically developing population is defined as two different psychopathologies other than cognitive impairments manifesting together. However, by this definition, this type of
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comorbidity within the ID population has yet to be explored extensively. Since comorbid psychopathology within the typically developing population is prevalent and of critical importance when designing treatment regimens (Olatunji et al., 2010), it appears appropriate that equal attention be given to this topic within those with ID. Several significant correlations were found between symptom clusters on the DASH-II. The three comorbid elevations for which there were the largest correlations (i.e., Organic and Mood, Mood and Mania, and PDD/Autism and Stereotypies) can be partially explained by an overlap in items on the subscales related to symptoms in each domain. The Organic and Mood subscales as well as the Mood and Mania subscales shared two identical items each, while there were four overlapping items between the PDD/Autism and Stereotypies subscales. However, the Organic and Mania subscales also have one overlapping item when no significant correlation was found between the two subscales. As such, though these overlapping items most certainly play a role in the significant correlations found, it is not suspected that they explain the full relationship. With respect to the correlation between the Mood and Mania subscales, an examination of bipolar disorder as described in the Diagnostic and statistical manual of mental disorders, 4th ed. – text revision (DSM-IV-TR; APA, 2000) exemplifies how there may be an expected relationship between endorsements on these two subscales. Bipolar disorder, which includes symptoms of mania and also often depression, has been found to occur in those with severe to profound ID (Matson, Terlonge, Gonza´lez, & Rivet, 2006; Ross & Oliver, 2003). Therefore in applied settings, a relationship between these two subscales would be expected and significant elevations on them concurrently may suggest that more extensive assessment for bipolar disorder be conducted. In regard to the significant relationship between the PDD/Autism and Stereotypies subscales, four of the items overlapped. Although this inherently increases the probability of finding a significant correlation between these subscales, this is not without good reason. Restricted and/or repetitive behaviors are subsumed under the third diagnostic criteria for a diagnosis of autistic disorder, which indicates that these individuals must present with either restrictive and/or repetitive behaviors, interests, or routines (APA, 2000). The co-occurrence of ASD symptoms and motor and vocal stereotypies has been well documented in the literature (MacDonald et al., 2007), thereby supporting the relation between these two variables. Furthermore, Tourette syndrome, which is characterized by multiple motor and vocal tics, has also been documented to cooccur with ASD (Canitano & Vivanti, 2007). The strongest correlations between symptom clusters were between the Organic and Mood subscales on the DASH-II. In the typically developing population, dementia and mood disorders have been noted to co-occur (Lauter & Dame, 1991). The same association has been found in those with ID (McGuire & Chicoine, 1996). Furthermore, the symptoms of dementia may present differently in those with ID so that they may more closely resemble symptoms of a mood disorder and as a result be more difficult to differentiate (McGuire & Chicoine, 1996). Several moderate correlations were found between subscales on the DASH-II. Interestingly, the Schizophrenia subscale was found to have moderate correlations with three other subscales – the Organic, Mood, and Mania subscales. Though these relationships appear less obvious at first glance, the diagnostic criteria for schizoaffective disorder may assist in explaining the relationship between these subscales. Such a diagnosis requires an individual to present with schizophrenia while also exhibiting periods of time during which diagnostic criteria are met for either mania or major depression (i.e., a mood disorder) (APA, 2000). As such, it is possible that a relationship exists between the Schizophrenia subscale and aforementioned subscales because of the increased possibility of receiving a schizoaffective disorder diagnosis when presenting with these symptoms. Lastly, the Impulse subscale was found to moderately correlate with both the PDD/Autism and Anxiety subscales. ASD symptomatology can be likened to difficulties with impulse control as impulse control problems may contribute to challenging behaviors (e.g., aggression, self-injurious behavior), which are commonly found to occur in the ASD population (Duncan et al., 1999; Emerson et al., 2001). Similarly, impulse control difficulties can be seen in some anxiety disorders such as obsessive compulsive disorder in which individuals may have difficulty inhibiting their compulsive behaviors (Hollander & Wong, 1995). Therefore, a correlation describing these relationships appears appropriate. Overall, within the current sample, it was found that 61.8% of participants had significant elevations on at least two of the eight subscales. The reader should be reminded, however, that in order to be included in the sample, participants needed to have at least one significant elevation on any one subscale. Therefore, this is not to say that 61.8% of all individuals with ID have two or more significant elevations on psychopathology symptoms. Furthermore, the DASH-II is only a screening tool for psychopathology, so that elevations do not necessarily indicate that diagnoses would be warranted. However, this does demonstrate that significant impairments across multiple domains of psychopathology occur relatively frequently within the ID population, much as they do in the typically developing population (Kessler, Berglund, & Demler, 2005). It was also found that the Impulse subscale was the most common to be significantly elevated across participants. Since impulse control difficulties may often be linked to the presence of challenging behaviors, which occur at a rate of 10–20% in the ID population (Emerson et al., 2001; Holden & Gitlesen, 2006; Lowe et al., 2007), this significant elevation appears appropriate. The significantly high proportion of individuals within the sample reaching clinical significance on this subscale is further explained when taking into consideration that the sample for this study came from a developmental center, suggesting that the participants likely exhibited behavioral difficulties interfering with their placement in the community. In regard to the subscale elevations that co-occurred with the Impulse subscale (i.e., Mood, Mania, and Anxiety), further investigation is needed to decipher whether or not this is due to true comorbid conditions or rather the presence of challenging behaviors affecting psychopathological symptom presentation. In sum, just as in the typically developing population, it seems that certain symptoms of psychopathology are likely to be associated with the ID population. Many of these associations can seemingly be explained by disorders which require
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significant impairments in multiple domains of psychopathology (e.g., schizoaffective disorder, bipolar disorder). On the other hand, some relationships may be indicative of true comorbid conditions in addition to the presence of ID. Future research should explore actual diagnoses within the ID population with respect to comorbidity. Additionally, since comorbid elevations were most common on the Impulse subscale in addition to the Mood, Mania, and Anxiety subscales, those engaging in frequent challenging behaviors may need to be analyzed separately as a means of clarifying the diagnostic picture in these individuals. References American Psychiatric Association. (2000). Diagnostic and statistical manual of mental disorders (4th ed. – text revision). Washington, DC: American Psychiatric Association. Armando, M., Nelson, B., Yung, A. R., Ross, M., Birchwood, M., Girardi, P., et al. (2010). Psychotic-like experiences and correlation with distress and depressive symptoms in a community sample of adolescents and young adults. Schizophrenia Research, 119, 258–265. Ashworth, M., Hirdes, J. P., & Martin, L. (2009). The social and recreational characteristics of adults with intellectual disability and pica living in institutions. Research in Developmental Disabilities, 30, 512–520. Bamburg, J. W., Cherry, K. E., Matson, J. L., & Penn, D. L. (2001). Assessment of schizophrenia in persons with severe and profound mental retardation using the Diagnostic Assessment for the Severely Handicapped (DASH II). Journal of Developmental and Physical Disabilities, 13, 319–332. Canitano, R., & Vivanti, G. (2007). Tics and Tourette syndrome in autism spectrum disorders. Autism, 11, 19–28. Deb, S., Thomas, M., & Bright, C. (2001). Mental disorder in adults with intellectual disability. I. 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Comorbid anxiety and mood disorders among persons with social anxiety disorder. Behaviour Research and Therapy, 40, 19–35. Fidler, D. J., & Jameson, J. S. (2008). Intellectual disability. Encyclopedia of Infant and Early Childhood Development, 154–164. Grant, B., Stinson, F., Dawson, D., Chou, P., Dufour, M., Compton, W., et al. (2004). Prevalence and co-occurrence of substance use disorders and independent mood and anxiety disorders. Archives of General Psychiatry, 61, 807–816. Hastings, R. P., Beck, A., Daley, D., & Hill, C. (2005). Symptoms of ADHD and their correlates in children with intellectual disabilities. Research in Developmental Disabilities, 26, 456–468. Holden, B., & Gitlesen, J. P. (2006). A total population study of challenging behaviour in the county of Hedmark. Norway: Prevalence, and risk markers. Research in Developmental Disabilities, 27, 456–465. Hollander, E., & Wong, C. M. (1995). Body dysmorphic disorder, pathological gambling, and sexual compulsions. Journal of Clinical Psychiatry, 56, 7–12. Kessler, R. C., Berglund, P., & Demler, O. (2005). Lifetime prevalence and age-of-onset distributions of DSM-IV disorders in the National Comorbidity Survey Replication. Archives of General Psychiatry, 62, 593–602. Kovacs, M., Paulauskas, S., Gatsonis, C., & Richards, C. (1988). Depressive disorders in childhood III. A longitudinal study of comorbidity with and risk for conduct disorders. Journal of Affective Disorders, 15, 205–217. Lauter, H., & Dame, S. (1991). Depressive disorders and dementia: The clinical view. Acta Psychiatrica Scandinavica, 83, 40–46. LoVullo, S. V., & Matson, J. L. (2009). Comorbid psychopathology in adults with Autism Spectrum Disorders and intellectual disabilities. Research in Developmental Disabilities, 30, 1288–1296. Lowe, K., Allen, D., Jones, E., Brophy, S., Moore, K., & James, W. (2007). Challenging behaviours: Prevalence and topographies. Journal of Intellectual Disability Research, 51, 625–636. MacDonald, R., Green, G., Mansfield, R., Geckeler, A., Gardenier, N., Anderson, J., et al. (2007). Stereotypy in young children with autism and typically developing children. Research in Developmental Disabilities, 28, 266–277. Matson, J. L. (1995). The Diagnostic Assessment for the Severely Handicapped-II. Baton Rouge, LA: Scientific Publishers Inc. Matson, J. L., & Nebel-Schwalm, M. S. (2007). Comorbid psychopathology with autism spectrum disorder in children: An overview. Research in Developmental Disabilities, 28, 341–352. Matson, J. L., & Shoemaker, M. (2009). Intellectual disability and its relationship to autism spectrum disorders. Research in Developmental Disabilities, 30, 1107– 1114. Matson, J. L., & Smiroldo, B. B. (1997). Validity of the mania subscale of the Diagnostic Assessment for the Severely Handicapped. Research in Developmental Disabilities, 18, 221–225. Matson, J. L., Smiroldo, B. B., & Hastings, T. L. (1997). Validity of the autism/pervasive developmental disorder subscale of the Diagnostic Assessment for the Severely Handicapped-II. Journal of Autism and Developmental Disorders, 28, 77–81. Matson, J. L., Terlonge, C., Gonza´lez, M. L., & Rivet, T. (2006). An evaluation of social and adaptive skills in adults with bipolar disorder and severe/profound intellectual disability. Research in Developmental Disabilities, 27, 681–687. McCarthy, J., Hemmings, C., Kravariti, E., Dworzynski, K., Holt, G., Bouras, N., et al. (2010). Challenging behavior and co-morbid psychopathology in adults with intellectual disability and autism spectrum disorders. Research in Developmental Disabilities, 31, 362–366. McGuire, D. E., & Chicoine, B. A. (1996). Depressive disorders in adults with Down syndrome. Habilitative Mental Healthcare Newsletter, 12, 26–27. Naragon-Gainey, K. (2010). Meta-analysis of the relations of anxiety sensitivity to depressive and anxiety disorders. Psychological Bulletin, 136, 128–150. Olatunji, B. O., Cisler, J. M., & Tolin, D. F. (2010). A meta-analysis of the influence of comorbidity on treatment outcome in the anxiety disorders. Clinical Psychology Review, 30, 642–654. Rojahn, J., Borthwick-Duffy, S. A., & Jacobson, J. W. (1993). The association between psychiatric diagnoses and severe behavior problems in mental retardation. Annals of Clinical Psychiatry, 5, 163–170. Ross, E., & Oliver, C. (2003). The assessment of mood in adults who have severe or profound mental retardation. Clinical Psychology Review, 23, 225–245. Sevin, J. A., Matson, J. L., Williams, D., & Kirkpatrick-Sanchez, S. (1995). Reliability of emotional problems with the Diagnostic Assessment for the Severely Handicapped (DASH-II). British Journal of Clinical Psychology, 34, 93–94. Smith, K. R. M., & Matson, J. L. (2010). Behavior problems: Differences among intellectually disabled adults with co-morbid autism spectrum disorders and epilepsy. Research in Developmental Disabilities, 31, 1062–1069. 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Contents lists available at ScienceDirect
Research in Developmental Disabilities
The relationship between psychopathology symptom clusters and the presence of comorbid psychopathology in individuals with severe to profound intellectual disability Alison M. Kozlowski a, Johnny L. Matson a,*, Megan Sipes a, Megan A. Hattier a, Jay W. Bamburg b a b
Department of Psychology, Louisiana State University, Baton Rouge, LA 70803, United States Pinecrest Supports and Services Center, Pineville, LA, United States
A R T I C L E I N F O
A B S T R A C T
Article history: Received 18 December 2010 Accepted 19 January 2011 Available online 4 March 2011
In the typically developing population, comorbid psychopathology refers to the cooccurrence of two different psychopathologies other than cognitive impairments. With respect to individuals with intellectual disability, comorbidity is often described as cognitive deficits and one additional psychopathology manifesting together. However, just as within the typically developing population, individuals with intellectual disability may also present with symptoms of two or more additional disorders. The presentation of these symptom clusters may similarly correlate. Therefore, the current study used the Diagnostic Assessment for the Severely Handicapped—II in order to examine relationships between psychopathological symptom clusters in adults with severe to profound intellectual disability. Additionally, we assessed comorbid presentation of disorders other than cognitive impairments in these same adults. Several symptom clusters were identified as being related with moderate to strong positive correlations. Furthermore, elevations on the Impulse subscale were noted to be the most prevalent in the current sample, with comorbid elevations most commonly occurring along the Mood, Mania, and Anxiety subscales. The significance of these findings is discussed. ß 2011 Elsevier Ltd. All rights reserved.
Keywords: Intellectual disability Mental retardation Comorbid psychopathology DASH-II
1. Introduction Individuals with intellectual disabilities (IDs) experience cognitive deficits as well as impairments in adaptive and social skills (Ashworth, Hirdes, & Martin, 2009; Soenen, VanBerckelaer-Onnes, & Scholte, 2009). In addition, challenging behaviors such as physical aggression, self-injurious behavior, and pica are fairly common in those with ID (Duncan, Matson, Bamburg, Cherry, & Buckley, 1999; Emerson et al., 2001). In many cases, aside from these challenging behaviors, individuals with ID also exhibit symptoms of comorbid psychopathology (Duncan et al., 1999; McCarthy et al., 2010; Smith & Matson, 2010; Sturmey, Laud, Cooper, Matson, & Fodstad, 2010a, 2010b). Estimates suggest that up to 4–40% of those with ID exhibit comorbidity which makes the topic an important area to investigate (Deb, Thomas, & Bright, 2001; Dekker & Koot, 2003; Rojahn, Borthwick-Duffy, Jacobson, 1993). In those with ID, some of the commonly seen mental health disorders include depression, attention-deficit/hyperactivity disorder, and anxiety disorders, among others (Deb et al., 2001; Dekker & Koot, 2003; Hastings, Beck, Daley, & Hill, 2005).
* Corresponding author. E-mail address: [email protected] (J.L. Matson). 0891-4222/$ – see front matter ß 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.ridd.2011.02.004
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While researchers have begun to explore comorbid diagnoses in people with ID, the definition of comorbidity is often in reference to the presence of ID along with one other form of psychopathology (Fidler & Jameson, 2008; LoVullo & Matson, 2009). For example, autism spectrum disorders (ASDs) and ID are commonly researched as the two have high rates of comorbidity (LoVullo & Matson, 2009; Matson & Nebel-Schwalm, 2007; Matson & Shoemaker, 2009). However, researchers have not yet investigated thoroughly the relationships between two different forms of psychopathology in addition to ID. This type of research is seen commonly in the typically developing population. For instance, a large body of literature examines the interaction between mood and anxiety disorders in those with normal cognitive functioning (Erwin, Heimberg, Juster, & Mindlin, 2002; Naragon-Gainey, 2010; Olatunji, Cisler, & Tolin, 2010). The interactions of other symptom classes have also been supported in the literature, such as substance use disorders and anxiety disorders (Grant et al., 2004), psychotic disorders and mood disorders (Armando et al., 2010), and mood disorders and conduct disorder (Kovacs, Paulauskas, Gatsonis, & Richards, 1988). Evidence supports the presence of one disorder or class of symptoms will affect the likelihood of other disorders and symptoms. As mentioned above, while the literature examining the influence of different types of comorbid symptoms is strong, this research using samples with ID is lacking. For example, it is unknown if elevations in one symptom category are likely to result in elevations of other symptoms related to a different type of psychopathology. However, some research has shown that in general, the presence of two or more disorders in addition to ID resulted in greater impairments in daily functioning (Dekker & Koot, 2003), which suggests that the interactions between symptom clusters is important. Therefore, the purpose of the current study was to examine the relationship between different symptoms of psychopathology in those with ID as well as the possibility of comorbid psychopathology in these individuals as defined in the typically developing population. 2. Method 2.1. Participants Seventy-six residents of a state-run developmental center in Louisiana served as the sample for this study. Participants ranged in age from 20 to 89 years with a mean age of 52.66 years (SD = 14.98). Since the DASH-II, which is described below, is designed for both individuals with severe and profound intellectual disability, all participants included in this study had prior diagnoses of either of these two. In regard to gender, 55.3% of the sample was male. The ethnicity of the participants was recorded as Caucasian (69.7%), African American (23.7%), or Unidentified (6.6%). 2.2. Measure The Diagnostic Assessment for the Severely Handicapped—II (DASH-II): The DASH-II is an informant-based assessment which screens psychopathological symptoms in individuals with severe to profound intellectual disability (Matson, 1995). The 84 questions which make up the DASH-II are divided into the following 13 subscales: Anxiety, Depression, Mania, PDD/Autism, Schizophrenia, Stereotypies/Tics, Self-Injurious Behavior, Elimination Disorders, Eating Disorders, Sleep Disorders, Sexual Disorders, Organic Problems, and Impulse Control and Miscellaneous Behavior Problems. This broad-based instrument measures the frequency, duration, and severity of these symptoms on a 0–2 scale. With respect to these indices, a 0 indicates no occurrence, less than 1 month, and no disruption or damages, respectively. A score of 1 corresponds to a frequency between 1 and 10 times, duration of 1–12 months, and a behavior that has not caused damage but has interrupted the activities of others. Meanwhile, a score of 2 along each index indicates an occurrence over 10 times, duration over 12 months, and causing injury or property damage, respectively. Interrater reliability of the DASH-II has been well established with percent agreement estimates for the frequency, duration, and severity dimensions as .86, .85, and .95, respectively (Sevin, Matson, Williams, & Kirkpatrick-Sanchez, 1995). In regard to test–retest reliability, percent agreement estimates across all items was .84 for both frequency and duration and .91 for severity. Validity for some individual subscales has also been established including the Mania (Matson & Smiroldo, 1997), Autism/PDD (Matson, Smiroldo, & Hastings, 1997), and Schizophrenia (Bamburg, Cherry, Matson, & Penn, 2001) subscales. For eight of the subscales (i.e., Impulse, Organic, Anxiety, Mood, Mania, Autism/PDD, Schizophrenia, and Stereotypies), cutoff scores have been indicated as those receiving a total frequency score at least one standard deviation above the mean (Matson & Smiroldo, 1997). For the remaining five subscales, severity scores are used to determine cutoffs. 2.3. Procedure Employees with at least a master’s level degree in psychology administered the DASH-II by clinical interview with a direct care staff familiar with the individual and knowledgeable of their behaviors. In order for the direct care staff to be qualified to serve as the informant, they must have known and worked with the individual being assessed for at least six months. The interviewer read the instructions, each item of the DASH-II, and possible response choices to the informant. 2.4. Statistical analysis For the current study, only the eight aforementioned subscales for which there have been statistically defined cutoff criteria were included (i.e., Impulse, Organic, Anxiety, Mood, Mania, PDD/Autism, Schizophrenia, and Stereotypies).
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1612 Table 1 Multiple bivariate correlations. Impulse Organic Pearson’s r p-value Anxiety Pearson’s r p-value Mood Pearson’s r p-value Mania Pearson’s r p-value PDD Pearson’s r p-value Schizophrenia Pearson’s r p-value Stereotypies Pearson’s r p-value *
Organic
Anxiety
Mood
Mania
PDD
Schizophrenia
.236 .040 .400 .000*
.242 .035
.330 .004
.735 .000*
.259 .024
.307 .007
.895 .000*
.258 .025
.697 .000*
.438 .000*
.218 .059
.145 .211
.186 .108
.240 .037
.256 .025
.379 .001*
.180 .119
.444 .000*
.381 .001*
.027 .814
.296 .009
.126 .280
.071 .540
.091 .432
.146 .208
.812 .000*
.064 .581
Clinically significant at .001 level.
Additionally, due to the small number of items on each subscale, participants missing any data were excluded from the analyses. Furthermore, inclusion criteria required the participant to have met cutoff on at least one of the eight subscales. This criterion was put in place to avoid significant correlations being noted due to zero or near-zero endorsements of all behaviors on the DASH-II. In order to determine whether or not there were relationships between comorbid psychopathology elevations on the DASH-II, two-tailed multiple bivariate correlations were computed with each subscale entered as the variables. To control for inflation of Type I error, a significance level of .05 divided by the number of simultaneous tests (n = 28) was chosen. Therefore, a significance level of .001 was used for all correlations. Next, concurrent frequency of clinically significant elevations on DASH-II subscales was explored to identify which clusters of psychopathology most commonly occurred together. 3. Results Of the 28 correlations analyzed, eight were found to be clinically significant. Symptom endorsements on the Impulse subscale were significantly positively correlated with elevations on the Anxiety (r = .400, p = .000) and PDD/Autism (r = .438, p = .000) subscales. Elevations on the Schizophrenia subscale were positively significantly correlated with those on the Organic (r = .379, p = .001), Mood (r = .444, p = .000), and Mania (r = .381, p = .001) subscales. Additionally, symptom endorsements on the Organic subscale were significantly positively correlated with elevations on the Mood subscale (r = .735, p = .000), those on the Mood subscale were significantly positively correlated with elevations on the Mania subscale (r = .697, p = .000), and elevations on the PDD/Autism subscale were significantly positively correlated with endorsements on the Stereotypies subscale (r = .812, p = .000). Please see Table 1 for a breakdown of correlation coefficients and associated significance levels for all correlations assessed. Next, a frequency count of all clinically significant subscale elevations on the DASH-II was compiled to identify those subscales which commonly co-occurred. Those individuals demonstrating only one clinically significant elevation on the DASHII comprised 38.2% of the total sample. The remaining 61.8% of the sample had clinically significant elevations on two or more subscales of the DASH-II. The most common clinically significant elevations were on the Impulse subscale (51.3%), followed by the Mania (40.8%) and Mood (39.5%) subscales. Individuals with two or three concurrent clinical elevations comprised 35.5% of the total sample and were investigated further with respect to the most common co-occurring clinically significant elevations. All participants with more than three clinically significant elevations were excluded because it was believed that these individuals displayed complex diagnostic pictures that did not demonstrate clear patterns with regard to comorbid psychopathologies. Of those individuals with two or three clinical elevations, 62.96% had elevations along the Impulse subscale. These individuals most commonly had concurrent elevations on the Anxiety, Mood, and/or Mania subscales. 4. Discussion The aim of the current study was to address the possibility of co-occurring psychopathological disorders within the ID population. Although ID co-occurring with another disorder is considered to be a comorbid diagnosis in and of itself (Duncan et al., 1999; McCarthy et al., 2010), comorbidity within the typically developing population is defined as two different psychopathologies other than cognitive impairments manifesting together. However, by this definition, this type of
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comorbidity within the ID population has yet to be explored extensively. Since comorbid psychopathology within the typically developing population is prevalent and of critical importance when designing treatment regimens (Olatunji et al., 2010), it appears appropriate that equal attention be given to this topic within those with ID. Several significant correlations were found between symptom clusters on the DASH-II. The three comorbid elevations for which there were the largest correlations (i.e., Organic and Mood, Mood and Mania, and PDD/Autism and Stereotypies) can be partially explained by an overlap in items on the subscales related to symptoms in each domain. The Organic and Mood subscales as well as the Mood and Mania subscales shared two identical items each, while there were four overlapping items between the PDD/Autism and Stereotypies subscales. However, the Organic and Mania subscales also have one overlapping item when no significant correlation was found between the two subscales. As such, though these overlapping items most certainly play a role in the significant correlations found, it is not suspected that they explain the full relationship. With respect to the correlation between the Mood and Mania subscales, an examination of bipolar disorder as described in the Diagnostic and statistical manual of mental disorders, 4th ed. – text revision (DSM-IV-TR; APA, 2000) exemplifies how there may be an expected relationship between endorsements on these two subscales. Bipolar disorder, which includes symptoms of mania and also often depression, has been found to occur in those with severe to profound ID (Matson, Terlonge, Gonza´lez, & Rivet, 2006; Ross & Oliver, 2003). Therefore in applied settings, a relationship between these two subscales would be expected and significant elevations on them concurrently may suggest that more extensive assessment for bipolar disorder be conducted. In regard to the significant relationship between the PDD/Autism and Stereotypies subscales, four of the items overlapped. Although this inherently increases the probability of finding a significant correlation between these subscales, this is not without good reason. Restricted and/or repetitive behaviors are subsumed under the third diagnostic criteria for a diagnosis of autistic disorder, which indicates that these individuals must present with either restrictive and/or repetitive behaviors, interests, or routines (APA, 2000). The co-occurrence of ASD symptoms and motor and vocal stereotypies has been well documented in the literature (MacDonald et al., 2007), thereby supporting the relation between these two variables. Furthermore, Tourette syndrome, which is characterized by multiple motor and vocal tics, has also been documented to cooccur with ASD (Canitano & Vivanti, 2007). The strongest correlations between symptom clusters were between the Organic and Mood subscales on the DASH-II. In the typically developing population, dementia and mood disorders have been noted to co-occur (Lauter & Dame, 1991). The same association has been found in those with ID (McGuire & Chicoine, 1996). Furthermore, the symptoms of dementia may present differently in those with ID so that they may more closely resemble symptoms of a mood disorder and as a result be more difficult to differentiate (McGuire & Chicoine, 1996). Several moderate correlations were found between subscales on the DASH-II. Interestingly, the Schizophrenia subscale was found to have moderate correlations with three other subscales – the Organic, Mood, and Mania subscales. Though these relationships appear less obvious at first glance, the diagnostic criteria for schizoaffective disorder may assist in explaining the relationship between these subscales. Such a diagnosis requires an individual to present with schizophrenia while also exhibiting periods of time during which diagnostic criteria are met for either mania or major depression (i.e., a mood disorder) (APA, 2000). As such, it is possible that a relationship exists between the Schizophrenia subscale and aforementioned subscales because of the increased possibility of receiving a schizoaffective disorder diagnosis when presenting with these symptoms. Lastly, the Impulse subscale was found to moderately correlate with both the PDD/Autism and Anxiety subscales. ASD symptomatology can be likened to difficulties with impulse control as impulse control problems may contribute to challenging behaviors (e.g., aggression, self-injurious behavior), which are commonly found to occur in the ASD population (Duncan et al., 1999; Emerson et al., 2001). Similarly, impulse control difficulties can be seen in some anxiety disorders such as obsessive compulsive disorder in which individuals may have difficulty inhibiting their compulsive behaviors (Hollander & Wong, 1995). Therefore, a correlation describing these relationships appears appropriate. Overall, within the current sample, it was found that 61.8% of participants had significant elevations on at least two of the eight subscales. The reader should be reminded, however, that in order to be included in the sample, participants needed to have at least one significant elevation on any one subscale. Therefore, this is not to say that 61.8% of all individuals with ID have two or more significant elevations on psychopathology symptoms. Furthermore, the DASH-II is only a screening tool for psychopathology, so that elevations do not necessarily indicate that diagnoses would be warranted. However, this does demonstrate that significant impairments across multiple domains of psychopathology occur relatively frequently within the ID population, much as they do in the typically developing population (Kessler, Berglund, & Demler, 2005). It was also found that the Impulse subscale was the most common to be significantly elevated across participants. Since impulse control difficulties may often be linked to the presence of challenging behaviors, which occur at a rate of 10–20% in the ID population (Emerson et al., 2001; Holden & Gitlesen, 2006; Lowe et al., 2007), this significant elevation appears appropriate. The significantly high proportion of individuals within the sample reaching clinical significance on this subscale is further explained when taking into consideration that the sample for this study came from a developmental center, suggesting that the participants likely exhibited behavioral difficulties interfering with their placement in the community. In regard to the subscale elevations that co-occurred with the Impulse subscale (i.e., Mood, Mania, and Anxiety), further investigation is needed to decipher whether or not this is due to true comorbid conditions or rather the presence of challenging behaviors affecting psychopathological symptom presentation. In sum, just as in the typically developing population, it seems that certain symptoms of psychopathology are likely to be associated with the ID population. Many of these associations can seemingly be explained by disorders which require
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significant impairments in multiple domains of psychopathology (e.g., schizoaffective disorder, bipolar disorder). On the other hand, some relationships may be indicative of true comorbid conditions in addition to the presence of ID. Future research should explore actual diagnoses within the ID population with respect to comorbidity. Additionally, since comorbid elevations were most common on the Impulse subscale in addition to the Mood, Mania, and Anxiety subscales, those engaging in frequent challenging behaviors may need to be analyzed separately as a means of clarifying the diagnostic picture in these individuals. References American Psychiatric Association. (2000). Diagnostic and statistical manual of mental disorders (4th ed. – text revision). Washington, DC: American Psychiatric Association. Armando, M., Nelson, B., Yung, A. R., Ross, M., Birchwood, M., Girardi, P., et al. (2010). 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