Epilepsy and Repetitive Behaviors in ASD

Background: Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder with a variable phenotype. Approximately 8-21% of individuals with ASD have epilepsy. Differentiating the complex ASD phenotype based on co-occurring symptom patterns may provide meaningful subgroups. Epilepsy and repetitive behaviors are present in ASD and may yield meaningful subgroups when examined in tandem. Understanding the ASD-epilepsy relationship has implications for identifying a genetic etiology of ASD and improving care.

Objectives: To determine whether repetitive behavior profiles among individuals with ASD are associated with frequency of epilepsy.

Methods: This is a cross-sectional study of symptom patterns of individuals with ASD from the Simons Simplex Collection (SSC). The SSC is a well-characterized collection of individuals with ASD from simplex families (i.e., one individual with ASD in the family). Data were collected at multiple clinics across the US using standard procedures. Our dataset consisted of 2683 participants with ASD from the SSC.

Participants were between 4-18 years of age at enrollment. The sample was predominantly male (86%) and white (79%). All procedures were approved by the respective local institutional review boards. The primary measures were derived from the Autism Diagnostic Interview-Revised (ADI-R), a semi-structured caregiver interview that assesses ASD symptoms, and medical history. Our analyses used 13 ADI-R items, which assess repetitive behaviors (RRBs) common to ASD (e.g., repetitive use of objects) and a measure of epilepsy from the ADI-R and medical history.

Results: We identified 145 (5.4%) individuals with epilepsy using previously published criteria. Across individual RRB items the frequency of epilepsy ranged from 5.1%-6.7%. For four RRB items, compulsions, unusual sensory interests, hand and finger mannerisms, and unusual attachments, the frequency of epilepsy was significantly higher among those with these RRB. Using a two-step clustering approach with previously identified RRB factors (Repetitive Sensory Motor Behavior, Insistence on Sameness) as inputs, we identified four high quality clusters of individuals. Among these clusters, the frequency of epilepsy ranged from 4.2% to 7.2%. While these differences were not statistically significant (p = 0.13), the group with the highest frequency of epilepsy was the most socially and behaviorally impaired. 

Conclusions: The frequency of epilepsy is ASD does not differ significantly among groups of individuals with different RRB profiles. However, at the item level, epilepsy was more frequent among individuals with compulsions and hand and finger mannerisms.  Further study is needed to develop subtypes among individuals with ASD for genetic studies.