Children with ASD frequently have co-occurring (comorbid) psychiatric conditions, with estimates as high as 70 to 84 percent. A Comorbid disorder is defined as a disorder that co-exists or co-occurs with another diagnosis so that both share a primary focus of clinical and educational attention. Research indicates that children with ASD have a high risk for meeting criteria for other disorders, such as Attention Deficit/Hyperactivity Disorder (ADHD), disruptive behavior disorders, mood, and anxiety disorders, all which contribute to overall impairment.
A study published in the Annals of General Psychiatry examined which psychiatric disorders are more frequently associated with higher functioning ASD. The authors conducted a systematic literature search to identify clinical studies from January, 2000 to December, 2011 that assessed psychiatric comorbidities in individuals with Asperger syndrome (AS) or high functioning autism (HFA). They also searched references from recent reviews and other reports identified by this search strategy, and selected those we judged relevant.
Several studies reported an association between AS/HFA and internalizing symptoms, in particular, anxiety, depression, and bipolar disorder. A bidirectional association has been identified between internalizing disorders and autistic symptoms. For example, both a higher prevalence of anxiety disorders has been found in AS and a higher rate of autistic traits has been reported in youths with mood and anxiety disorders. Another study showed that individuals with AS displayed more social anxiety symptoms compared to healthy control individuals, even if these symptoms were clinically overlapping with the characteristic social problems typical of AS. Research also suggests that adolescents and young adults with HFA show a higher prevalence of bipolar disorders as compared to controls.
Depression is one of the most common comorbid syndromes observed in individuals with ASD, particularly higher functioning youth. An evaluation of psychiatric comorbidity in young adults with AS revealed that 70% had experienced at least one episode of major depression and 50% reported recurrent major depression. Although another documented association is with Obsessive-Compulsive Disorder (OCD), it is difficult to determine whether observed obsessive-repetitive behaviors are an expression of a separate, comorbid OCD, or an integral part of the core symptoms of AS. An additional study investigated the presence of DSM-IV- defined bipolar disorder in adolescents and young adults with HFA and found that adolescents and young adults with HFA show a higher prevalence of bipolar disorders as compared to controls.
An association between AS/HFA and Attention-Deficit Hyperactivity Disorder (ADHD) and other externalizing disorders such as disruptive behavior and conduct disorders has been reported. For example, a study of comorbid psychiatric disorders in children with AS/HFA found that approximately 71% of cases had a least one comorbid psychiatric disorder, with the most common comorbidities being social anxiety (29%), ADHD (28%), and Oppositional Defiant Disorder (28%). One of the most controversial comorbidities in children with AS/HFA is the co-occurrence of Attention Deficit Hyperactivity Disorder (ADHD). Although there continues to a debate about ADHD comorbidity in ASD, research, practice and theoretical models suggest that comorbidity between these disorders is relevant and occurs frequently. For example, a study comparing the rate and type of psychiatric comorbidity in children and adolescents HFA/AS found that the most common disorder in both groups was ADHD. Although the DSM-IV-TR hierarchical rules prohibit the concurrent diagnosis of ASD/PDD and ADHD, there is a relatively high frequency of impulsivity and inattention in children with higher functioning ASD. In fact, ADHD is a relatively common initial diagnosis in young children with ASD. Some researchers have suggested that a subgroup of individuals on the autism spectrum also has ADHD.
Tourette Syndrome (TS) and other tic disorders have been found to be a comorbid condition in many children with ASD. A Swedish study showed that 20% of all school-age children with AS met the full criteria for TS. Although the association between autism and seizure disorder is not as yet firmly established, there appears to be a higher incidence of seizures in children with autism compared to the general population. The comorbidity of ASD and psychotic disorders has also been examined. A study of children with ASD who were referred for psychotic behavior and given a diagnosis of schizophrenia showed that when psychotic behaviors were the presenting symptoms, depression and not schizophrenia, was the likely diagnosis. Thus, individuals with AS and HFA may present with characteristics that could lead to a misdiagnosis of schizophrenia and other psychotic disorders.
The environmental context deferentially affects individuals with AS/HFA and may be considered a factor that influences the onset, expression and severity of a comorbid psychiatric disorder. Parents of children with AS/HFA have been shown to have an impaired sense of well being, and to display a lower quality of life when compared to parents of children with other psychiatric and neurological disorders, such as cerebral palsy or mental retardation. Moreover, mothers of children with ASD were found to perceive a higher level of stress than fathers which was shown to be related to peculiar behavioral characteristics of the child, such as higher hyperactivity and conduct problems. Other studies have also reported elevated rates of anxiety-related personality traits among the relatives of AS/HFA participants. Elevated anxiety and stress levels in the parents of children with ASD can be considered as an important environmental factor that might serve to trigger a genetic predisposition for a comorbid anxiety or depressive disorder. Therefore, investigating the psychiatric family history may inform about the comorbidity risk.
Assessment of co-occurring behavior/emotional problems is challenging, because we have no specific autism-specific tools designed for this purpose. Although various psychometric instruments, such as clinical interviews, self-report questionnaires and checklists, are widely used to assist in diagnosis, these diagnostic tools are designed and standardized to identify psychopathological symptoms in the general population, and may not be appropriate and valid for use with AS/HFA. Likewise, their administration may be problematic in that individuals with AS/HFA may have difficulties in sustaining a reciprocal conversation, reporting events, and lack an understanding and empathy for the feeling of others. When assessment tools are adapted to evaluate psychiatric comorbidity in persons with ASD, they result in several obvious limitations. The aforementioned studies illustrate the need for psychometric tools specifically designed to assess psychiatric disorders in the ASD population.
Children and youth with ASD frequently have comorbid psychiatric conditions, with rates significantly higher than would be expected from the general population. The most common co-occurring diagnoses are anxiety and depression, attention problems, and disruptive behavior disorders. The core symptoms of ASD can often mask the symptoms of a comorbid condition. Thus, the current challenge for practitioners is to determine if the symptoms observed in ASD are part of the same dimension (e.g., the autism spectrum) or whether they represent another psychiatric disorder. Further research should include longitudinal studies to examine whether individuals with ASD have an increased risk or a constitutive predisposition to develop psychiatric disorders or whether the incidence of onset is similar to normal population. Although assessment tools are limited, comorbid problems should be assessed whenever significant behavioral issues (e.g., inattention, mood instability, anxiety, sleep disturbance, aggression) become evident or when major changes in behavior are reported. Coexisting disorders should also be carefully investigated when severe or worsening symptoms are present that are not responding to traditional methods of intervention.
Mazzone et al.: Psychiatric comorbidities in asperger syndrome and high functioning autism: diagnostic challenges. Annals of General Psychiatry 2012 11:16. doi:10.1186/1744-859X-11-16
Wilkinson, L. A. (2010). A best practice guide to assessment and intervention for autism and Asperger syndrome in schools. London: Jessica Kingsley Publishers.
Lee A. Wilkinson, PhD, CCBT, NCSP is author of the award-winning book, A Best Practice Guide to Assessment and Intervention for Autism and Asperger Syndrome in Schools, published by Jessica Kingsley Publishers. He is also editor of a text in the APA School Psychology Book Series, Autism Spectrum Disorder in Children and Adolescents: Evidence-Based Assessment and Intervention in Schools and author of the book, Overcoming Anxiety and Depression on the Autism Spectrum: A Self-Help Guide Using CBT. His latest book is A Best Practice Guide to Assessment and Intervention for Autism Spectrum Disorder in Schools (2nd Ed.).
© Lee A. Wilkinson, PhD