High prevalence of bipolar disorder comorbidity in adolescents and young adults with high-functioning autism spectrum disorder: a preliminary study of 44 outpatients.

BACKGROUND Psychiatric comorbidity of autism spectrum disorder (ASD) has not been well examined. METHODS 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 Sixteen patients (36.4%) were diagnosed with mood disorder. Of these 16 patients, four were diagnosed as having major depressive disorder, two patients as bipolar I disorder, six patients as bipolar II disorder, and four patients as bipolar disorder not otherwise specified. Bipolar disorder accounted for 75% of cases. Twelve patients had Asperger disorder and four 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. CONCLUSIONS 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.