Shared Affective Instability in Autism Spectrum Disorder and Bipolar Disorder

Background: A subset of children with autism spectrum disorder (ASD) present with emotional dysregulation that resembles the affective instability (AI) symptoms observed in bipolar disorder (BD). A growing literature suggests co-occurring disorders and possible morbidity or etiologic overlap between ASD and BD. However, this overlap has not been well defined. A better description of AI may help elucidate symptom and etiological similarities between BD and ASD and facilitate the identification of potential biomarkers and treatment targets.

Objectives: To use K-SADS variables to study AI symptoms in children with ASD and children with BD thus delineating a domain of affective instability.

Methods: Children between 7 and 13 years with either DSM-IV ASD or BD, recruited for separate studies, received assessments including: Kiddie-Schedule for Affective Disorders and Schizophrenia (K-SADS), the Autism Diagnostic Interview (ADI-R), and the DSM-IV Asperger’s/Autism Checklist. Nineteen symptoms from the K-SADS were selected as representative of AI based on face validity. The ASD and BD groups were compared for the frequency of these AI symptoms.

Results: As expected, K-SADS symptoms of AI were more prevalent in the BD group. However, a subset of the ASD group also demonstrated a high frequency of AI symptoms. A cluster of eight symptoms displaying the greatest overlap between the two groups including acts before thinking, distractibility, depressed affect, grandiosity, inappropriate affect, decreased sleep, elated mood, and flight of ideas had an average frequency of 47% in the BD group, 26% in the ASD group, and 3% in the control group. Symptoms of AI were extreme enough in 13% of children with ASD to warrant a secondary lifetime diagnosis of BD.

Conclusions: A subset of children with ASD has significant AI resembling BD. Biomarker research may help identify overlapping etiopathogenesis of AI across DSM disorders.