Background: Psychiatric comorbidity of autism spectrum disorder (ASD) has not been well examined.
Method: Mood disorders in 44 consecutive outpatients with high-functioning ASD were examined at a university hospital according to DSM-IV. Inclusion criteria were an IQ of 70 or higher on the Wechsler Intelligence Scale and age of 12 years or over.
Results: 16 patients (36.4%) were diagnosed with mood disorder. Of these 16 patients, 4 were diagnosed as having major depressive disorder, two patients as bipolar I disorder, 6 patients as bipolar II disorder, and 4 patients as bipolar disorder not otherwise specified. Bipolar disorder accounted for 75% of cases. 12 patients had Asperger disorder and 4 patients had pervasive developmental disorder not otherwise specified. None of the patients had autistic disorder.
Limitations: The sample size was small. We could not use ‘Autism Diagnostic Interview—Revised’. Referral bias could not be avoided in this study.
Conclusion: The major comorbid mood disorder in patients with high-functioning ASD is bipolar disorder and not major depressive disorder. The autistic spectrum may share common vulnerability genes with the bipolar spectrum.
[Keywords: adolescent, autism spectrum disorder, bipolar disorder, comorbidity, young adult]