The Longitudinal Course of Mood and Psychosocial Functioning in Youth with Comorbid Bipolar and Autism Spectrum Disorders

Background: Autism Spectrum Disorder (ASD) is often clinically associated with disturbances of mood and emotion. There is growing evidence of elevated rates of comorbidity between ASD and other psychiatric disorders, particularly Bipolar Disorder (BP). The recognition and treatment of comorbid BP in individuals with ASD, despite its clinical importance, has been hampered by a dearth of phenomenological data. A small number of cross-sectional studies suggest increased impairments and a higher prevalence of atypical features, but little is known about the longitudinal course of BP in youths with ASD.

Objectives:   To provide the first longitudinal characterization of mood and psychosocial functioning in youth with comorbid ASD and BP.

Methods:   The Course and Outcome of Bipolar Youth (COBY) study recruited youths ages 7 to 17 years with DSM-IV BPI, II, or operationally-defined BP-NOS. Subjects were comprehensively assessed using structured diagnostic interviews and a wide range of non-overlapping measures covering multiple dimensions of functioning. This study included a total of 368 youths with at least 4 years of follow-up (average ~9 years) using the Longitudinal Interval Follow-up Evaluation. Subgroup analysis was conducted, comparing youth with (BP+ASD) and without ASD on clinical presentation, percentage of time with mood symptomatology, and psychosocial functioning.  

Results:   Thirty youth (~8%) met DSM IV criteria for ASD. Duration of BP symptoms prior to entry into the study was ~4 years for both groups, but BP+ASD youth were, on average, 2 years younger at symptom onset and intake. As is typically observed in clinical cohorts, the male to female ratio was ~1:5 for BP+ASD youth vs 1:1 for BP youth. Additional diagnostic comorbidity was common, with 87% of BP+ASD youth also meeting criteria for ADHD. Similar to previous studies, BP+ASD youth had significantly higher T-scores on several syndrome scales of the intake Child Behavior Checklist including; withdrawn, social, thought, and attention problems. Over time, the proportion of predominantly euthymic youth in both groups increased and episode recurrence decreased. BP+ASD youth spent significantly more time with sub-syndromal mixed symptoms and had worse psychosocial functioning, especially with respect to friendships. Distribution between BP subtypes and lifetime worst episode severity were similar for both groups. BP+ASD youths exhibited typical BP mood symptoms but were found to have a higher prevalence of social withdrawal, poor mood reactivity (activity-related transient improvements in negative mood), and a broad range of manic symptoms (e.g. grandiosity, elated and labile mood, distractibility, and motoric activation). Differences between BP and BP+ASD youth on most factors were most prominent during the first few years and decreased over time.

Conclusions:   Youth with comorbid BP and ASD exhibited typical BP mood symptoms but earlier onset, mixed symptom presentation, and additive functional impairments. Significant amelioration of clinical symptoms and psychosocial impairment occurs over time, suggesting that early recognition and treatment of mood disorders in youth with ASD may improve clinical outcomes.