Challenging behavior and co-morbid psychopathology in adults withintellectual disability and autism spectrum disorders

Jane McCarthy a, Colin Hemmings a, Eugenia Kravariti b, Katharina Dworzynski c,Geraldine Holt a, Nick Bouras a, Elias Tsakanikos a,*a Estia Centre, Institute of Psychiatry, King’s College London, UKb NIHR Biomedical Research Centre, Institute of Psychiatry, King’s College London, UKc Child and Adolescent Psychiatry, Institute of Psychiatry, King’s College London, UK

1. Introduction

Intellectual disability (ID) and autism spectrum disorders (ASDs) often co-occur at high rates and the relationshipbetween the two conditions is complex (Berney, 2004; Matson & Shoemaker, 2009). The study of co-morbidpsychopathology in ID and ASD has recently received increased attention (Bradley, Summers, Wood, & Bryson, 2004;Brereton, Tonge, & Einfeld, 2006; La Malfa et al., 2007; LoVullo & Matson, 2009; Melville et al., 2008; Tsakanikos et al., 2006)highlighting the need for understanding mental health and associated risk factors in this population. Despite the fact thatadults with ID and ASD often present challenging behaviors (Matson, Kiely, & Bamburg, 1997; Murphy et al., 2005) therelationship between challenging behavior and co-morbid psychopathology in people with ASD remains poorly understood.

Severity of ID and presence of ASD are independently associated with presence of challenging behaviors (Dawson,Matson, & Cherry, 1998; O’Brien & Pearson, 2004; Reese, Richman, Belmont, & Morse, 2005). These behavioral problems canbe viewed either as ‘behavioral equivalents’ of mental health problems (Clarke & Gomez, 1999) or as relatively independentconditions (Hemmings, Gravestock, Pickard, & Bouras, 2006; Hill & Furniss, 2006) which persist over time (Murphy et al.,2005).

Research in Developmental Disabilities 31 (2010) 362–366

A R T I C L E I N F O

Article history:

Received 23 September 2009

Accepted 1 October 2009

Keywords:

Autism spectrum disorders

Pervasive developmental disorder

Challenging behavior

Intellectual disabilities

Psychopathology

A B S T R A C T

We investigated the relationship between challenging behavior and co-morbid

psychopathology in adults with intellectual disability (ID) and autism spectrum disorders

(ASDs) (N = 124) as compared to adults with ID only (N = 562). All participants were first

time referrals to specialist mental health services and were living in community settings.

Clinical diagnoses were based on ICD-10 criteria and presence of challenging behavior was

assessed with the Disability Assessment Schedule (DAS-B). The analyses showed that ASD

diagnosis was significantly associated with male gender, younger age and lower level of ID.

Challenging behavior was about four times more likely in adults with ASD as compared to

non-ASD adults. In those with challenging behavior, there were significant differences in

co-morbid psychopathology between ASD and non-ASD adults. However, after controlling

for level of ID, gender and age, there was no association between co-morbid

psychopathology and presence of challenging behavior. Overall, the results suggest that

presence of challenging behavior is independent from co-morbid psychopathology in

adults with ID and ASD.

� 2009 Elsevier Ltd. All rights reserved.

* Corresponding author. Tel.: +44 0 20 3228 9745.

E-mail address: elias.tsakanikos@kcl.ac.uk (E. Tsakanikos).

Contents lists available at ScienceDirect

Research in Developmental Disabilities

0891-4222/$ – see front matter � 2009 Elsevier Ltd. All rights reserved.

doi:10.1016/j.ridd.2009.10.009

The presence of challenging behaviors may hinder diagnosis of co-morbid psychopathology in those with ASD or mayincrease the prevalence rates of specific mental health problems as a result of psychological and social interacting factors.However, there is little evidence on the relationship between challenging behaviors and the presence of co-morbidpsychopathology in adults with ID and ASD. Therefore, the present study examined whether the presence of challengingbehavior in adults with ID and ASD would be associated with increased or decreased rates of co-morbid psychopathology ascompared to adults with ID only.

2. Methods

2.1. Participants

Participants were 124 adults with ID who were clinically diagnosed with ASD and 562 adults with ID only. The age rangewas between 18 and 65, 60% were males (Table 1). All participants were consecutive referrals for assessment to a SpecialistMental Heath Service of South-East London. Referrals came 41.6% from Social Services, 36.9% from Primary Care and 21.5%from Generic Mental Health Services. Two psychiatrists both specialists in ID and mental health agreed on the diagnosispervasive developmental disorder and/or psychiatric disorder by applying ICD-10 clinical criteria using information gainedfrom interviews with key informants and the patients. The interviews were undertaken as part of the clinical assessment andincluded historical details from past medical and other records.

2.2. Data recording

Psychiatric diagnosis was coded according to the following major ICD-10 categories: schizophrenia spectrum disorder(F20-27), personality disorder (F60-69), anxiety (F40-48), depressive disorder (F32-39), adjustment reaction (F43), anddementia (F00-03). Other recorded variables were: age, gender, epilepsy and degree of ID. The degree of ID was coded on ICD-criteria into mild (F70), moderate (F71) or severe (F72-73) using information available on adaptive and intellectualfunctioning.

2.3. Assessment of challenging behavior

Challenging behavior was assessed through the DAS behavioral problems scale (DAS-B) as included in DisabilityAssessment Schedule (DAS) (Holmes, Shah, & Wing, 1983), which was developed to evaluate the level of functioning inpeople with intellectual disabilities. In this scale, behavioral problems are defined as any situation when members of staffhave to intervene, causing upset to others, or having marked effect on the social atmosphere. Ratings were completed by keyinformants, such as family and professional carers. DAS-B had good internal reliability (Cronbach’s Alpha = .87) in the presentsample. Challenging behavior was operationally defined as the presence of at least one serious behavioral problem asassessed by DAS-B for at least 3 months (Holmes et al., 1983) with 3 months being considered a sufficient period of time toidentify any significant problems present before the initial clinical assessment.

Table 1

Number and percentages of patients with and without ASD by gender, age, level of intellectual disability (ID) and challenging behavior.

Variable ASD

Yes n (%) No n (%) Total n (%)

Gender

Male 86 (69.3) 328 (58.4) 414 (60.3)

Female 38 (30.6) 234 (41.6) 272 (39.65)

Age (years)

<24 61 (49.19) 173 (30.78) 234 (34.1)

25–34 38 (30.64) 119 (21.17) 157 (22.8)

35–44 15 (12.09) 131 (23.30) 146 (21.3)

45–54 4 (3.22) 77 (13.70) 81 (11.8)

55+ 6 (4.83) 62 (11.03) 68 (9.91)

Level of ID

Mild (F70) 52 (41.9) 381 (67.8) 433 (63.1)

Moderate (F71) 42 (33.9) 116 (20.6) 158 (23.0)

Severe (F72-73) 30 (24.2) 65 (11.6) 95 (13.8)

Challenging behavior

Presence 109 (87.9) 349 (62.1) 458 (66.8)

Absence 15 (12.1) 213 (37.9) 228 (33.2)

J. McCarthy et al. / Research in Developmental Disabilities 31 (2010) 362–366 363

2.4. Data analysis

The Statistical Package for Social Sciences (SPSS 16) was employed. Before the analysis, dummy variables were created foreach variable, coded as presence (1) or absence (0). The obtained categorical data were initially analysed by Chi-square teststo examine statistically significant differences between the ASD and non-ASD group. This was in order to assess separatelyeach variable (in which the previous analysis revealed statistical differences) as an independent predictor of ASD. To explorethe relationship between psychiatric disorders and challenging behavior, binary logistic regression was performed using astepwise forward method. The variables were added successively according to the magnitude of their correlation with thedependent variable, and then were successively removed until the predictive ability of the regression model, indexed by themodel Chi-square, was not significantly improved. A second binary logistic regression was performed to assess the presentvariables as predictors of challenging behavior.

In the first regression analysis, the presence of ASD was the dependent measure. The parameters gender (male 0/female1), age (�35/<35), ID level (severe/non-severe), presence of challenging behavior, as well as the relevant psychiatriccategories (i.e. ‘schizophrenia spectrum disorder’ and ‘absence of psychiatric disorder’), each coded as a binary variable, wereentered in the equation as predictor variables. In the second regression analysis, the presence of challenging behavior wasthe dependent measure.

3. Results

Table 1 presents the proportion of participants with and without ASD by gender, age, and level of ID. Overall, adults withASD were significantly younger (Chi-square = 33.45, df = 4, p< .0001) and were more likely to have moderate or severe ID(Chi-square = 30.18, df = 2, p< .0001). As expected, there were an increased proportion of males among adults with ASD (Chi-square = 5.19, df = 1, p = .02). Moreover, a significantly larger proportion of adults with ASD had challenging behavior (Chi-square = 30.48, df = 1, p< .0001).

The proportion of psychiatric diagnosis by the presence of ASD and challenging behavior is presented in Table 2. In thoseindividuals with challenging behavior there were significant differences in co-morbid psychopathology between the ASDand non-ASD group (Chi-square = 16.78, df = 7, p = .02). Specifically, adults with challenging behavior and ASD were lesslikely to receive a diagnosis of schizophrenia spectrum (Chi-square = 4.87, df = 1, p = .03) than those with challengingbehavior but without ASD and those adults with challenging behavior and ASD were more likely to have no otherdiagnosable disorder (Chi-square = 16.49, df = 1, p< .001) as compared with their non-ASD counterparts with challengingbehavior. Correspondingly, people with ASD but without challenging behavior were more likely to receive a schizophreniaspectrum diagnosis (Chi-square = 5.27, df = 1, p = .02) than their non-ASD counterparts. No other differences reachedstatistical significance (all ps> .10).

3.1. Multi-variate analyses

The previous analyses revealed group differences in terms of age, gender, level of ID and challenging behavior betweenpeople with and without ASD. Furthermore, the presence of challenging behavior revealed some group differences in terms

Table 2

Number and percentages of patients with and without ASD by psychiatric diagnosis and presence of challenging behavior.

ASD

Yes n (%) No n (%) Total n (%)

With challenging behavior

Psychiatric diagnosis

Schizophrenia spectrum (F20-27) 1 (10.1) 67 (19.2) 78 (17.0)

Personality disorder (F60-69) 4 (3.7) 23 (6.6) 27 (5.9)

Anxiety (F40-48) 4 (3.7) 23 (6.6) 27 (5.9)

Depressive disorder (F32-39) 6 (5.5) 31 (8.9) 37 (8.1)

Adjustment reaction (F43) 3 (2.8) 15 (4.3) 18 (3.9)

Dementia (F00-03) 1 (0.9) 8 (2.3) 9 (2.0)

Other diagnosis 3 (2.8) 13 (3.7) 16 (3.5)

No diagnosable disorder 77 (70.6) 169 (48.4) 246 (53.7)

Without challenging behavior

Psychiatric diagnosis

Schizophrenia spectrum (F20-27) 6 (40.0) 35 (16.4) 41 (18.0)

Personality disorder (F60-69) 0 (0.0) 4 (1.9) 4 (1.8)

Anxiety (F40-48) 1 (6.7) 21 (9.9) 22 (9.6)

Depressive disorder (F32-39) 3 (20.0) 38 (17.8) 41 (18.0)

Adjustment reaction (F43) 0 (0.0) 11 (5.2) 11 (4.8)

Dementia (F00-03) 0 (0.0) 6 (2.8) 6 (2.6)

Other diagnosis 0 (0.0) 6 (2.8) 6 (2.6)

No diagnosable disorder 5 (33.3) 92 (43.2) 97 (42.5)

J. McCarthy et al. / Research in Developmental Disabilities 31 (2010) 362–366364

of the presence of schizophrenia spectrum disorder and no diagnosable psychiatric diagnosis. To further examine the abovepattern of results, while controlling for the previously observed differences between the critical variables, a set of forwardlogistic regression analyses (see Section 2.4) was performed. In all regression equations all variables in which there weregroup differences were entered as predictor variables.

The results from the logistic regression analyses are summarized in Table 3. In the first regression analysis, ASD(presence/absence) was entered as the dependent measure. The regression model was significant (x2 = 86.83, df = 4,p< .0001, �2 Log likelihood = 561.49) accounting for about 19% of the variance (Nagelkerke R2). Gender (male), age (�35),level of ID (severe) and presence of challenging behavior were significant independent predictors. In the second logisticanalysis challenging behavior (presence/absence) was entered as the dependent measure. The overall model was significant(x2 = 46.88, df = 2, p< .001, �2 Log likelihood = 825.48) accounting for about 9% of the variance (Nagelkerke R2). Level of ID(severe) and ASD were the only significant individual predictors.

The results from the above multi-variate analyses suggest that in the present sample of adults with ID, those with autismwere more likely to be males of younger age (less then 35) with severe level of ID and challenging behavior. However,challenging behavior per se was equally likely among males and females, among younger and older patients, and amongthose with and without an additional ICD-10 psychiatric diagnosis; only the presence of ASD and severe ID reliably predictedchallenging behavior.

4. Discussion

The study benefited from a large sample of adults with ID with clinical diagnoses made by experienced clinicians usingICD-10 criteria and in which challenging behaviors were rated independently by key informants, such as family andprofessional carers. Challenging behavior was about four times more likely in adults with ASD as compared to non-ASDadults. The logistic regression analysis also demonstrated that those with ASD were younger and more likely to be male inline with other studies (e.g. Brereton et al., 2006). Furthermore, the presence of ASD was associated with severity of ID(Dawson et al., 1998; O’Brien & Pearson, 2004; Reese et al., 2005).

The key finding of this study is that a diagnosis of ASD predicted the presence of challenging behaviors whereas adiagnosis of mental illness did not. Those with ASD and challenging behavior were not more likely to receive a psychiatricdiagnosis than those with ASD but without challenging behaviors and were less likely to receive a schizophrenia spectrumdiagnosis. Other studies to date have shown no increased risk for psychosis in adults with ASD and in fact they are less likelyto receive this diagnosis (Lunsky, Gracey, & Bradley, 2009; Tsakanikos et al., 2006). It may be that experiencing of psychoticsymptoms in an individual with ASD and ID may impact on challenging behaviors or it may be the presence of challengingbehaviors in an individual with ASD may make the diagnosis of psychotic symptoms more difficult.

The study of patterns of behaviors in those with ASD is an area of increasing interest such as repetitive and stereotypedbehaviors (Carcani-Rathwell, Rabe-Hasketh, & Santosh, 2006). Perry, Marston, Hinder, Munden, and Roy (2001) tried toidentify patterns of behavior that may indicate a depressive illness in those with ASD and ID. Association betweenchallenging behavior and psychiatric disorder in specific syndromes such as Down syndrome has been looked at but with nolink found (McCarthy & Boyd, 2001). One of the difficulties is that individuals with ASD vary in their cognitive abilities,adaptive functioning and severity of autistic features. It is not well understood how these differences and factors such asgender and age impact on the presentation and development of psychiatric disorders and challenging behaviors in thosewith ASD.

Over recent years the study of psychopathology in people with ID has moved direction from determining the prevalenceof psychopathology and behavioral problems to understanding risk factors (Dykens, 2001). Variables such as age, gender andlevel of ID have not found to affect the level of overall psychopathology in young people with ASD and ID (Brereton et al.,2006), although it has been suggested that adults with ASD and ID and problem behaviors are less likely to recover over a 2-year period (Cooper, Smiley, Morrison, Williamson, & Allan, 2007). In the current study, severity of ID and presence of ASDwere the only significant predictors of challenging behavior.

Table 3

Regression models for predicting autism and challenging behavior.

Variable B SE Exp (B) 95% CI p

ASD

Gender .53 .23 .59 .38–.92 =.019

Age �1.19 .25 23.26 .19–.49 <.001

ID level .88 .214 2.42 1.59–3.68 <.001

Challenging behavior 1.28 .297 3.55 1.98–6.35 <.001

(Constant) �1.76 .419

Challenging behavior

ID level .622 .184 1.86 1.30–2.67 <.001

ASD 1.353 .292 3.87 2.18–6.86 <.001

(Constant) �1.048 .328

J. McCarthy et al. / Research in Developmental Disabilities 31 (2010) 362–366 365

Some possible limitations in this study should be also pointed out. The diagnosis of ASD during the clinic assessment mayhave overshadowed other psychiatric diagnoses such as attention deficit hyperactive disorder and obsessive compulsivedisorder. For example, Lowry (1997) has proposed the term ‘behavioral overshadowing’ to emphasise the identification ofpsychopathology only as ‘learned behavior’ rather than also as a possible symptom or sign of mental illness. Although theassessors were highly experienced clinicians it is possible that the presence of challenging behaviors complicated thepresentation to such an extent that it reduced the likelihood of them being able to make an additional psychiatric diagnosis.Furthermore, the present findings are based on a referred population so is not an epidemiological study, but health serviceresearch examining service implications in real clinical settings.

Overall, the present findings support the suggestion that challenging behavior and mental health problems are relativelyindependent conditions (Hemmings et al., 2006; Hill & Furniss, 2006). The implications of the study are importantparticularly in view of the recent finding that two commonly used anti-psychotic drugs are no better than placebo inreducing challenging behavior in adults with ID including those with ASD (Tyrer et al., 2008). Therefore, management ofchallenging behavior symptoms in this population when no other mental health problem is identified requires furtherinvestigation of therapeutic approaches and evaluation of treatment options.

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