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 Psychiatryexamined which psychiatric disorders are more frequently associated with higher functioning ASD. The authors conducted a systematic literature search to identify clinical studies that assessed psychiatric comorbidities in individuals with high functioning autism ASD. They also searched references from recent reviews and other reports identified by this search strategy, and selected those we judged relevant.
Internalizing Problems
Several studies reported an association between ASD 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 ASD and a higher rate of autistic traits has been reported in youths with mood and anxiety disorders. Another study showed that individuals with ASD displayed more social anxiety symptoms compared to healthy control individuals, even if these symptoms were clinically overlapping with the characteristic social problems typical of ASD. Research also suggests that adolescents and young adults with ASD 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 ASD and found that adolescents and young adults with ASD show a higher prevalence of bipolar disorders as compared to controls.
Externalizing Problems
An association between ASD 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 ASD 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 ASD 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 with ASD found that the most common disorder was ADHD. Although the previous DSM-IV-TR hierarchical rules prohibited 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.
Other Comorbidities
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 ASD 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 ASD may present with characteristics that could lead to a misdiagnosis of schizophrenia and other psychotic disorders.
Conclusion
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
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.
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