The Assessment of and Differences among Intellectually Disabled Adults with Comorbid Autism Spectrum Disorders and Epilepsy

Background: Adults with intellectual disabilities (ID) often have comorbid Autism Spectrum Disorders (ASD) and neurological conditions such as epilepsy. Previous studies indicating of this comorbidity tend to stop short of addressing these disorders’ impact on the full range of psychosocial issues, particularly in adult samples. Although psychopathology, behavior problems, and impaired social behaviors are common among those who live in institutional settings; identifying differences among adults with a single disorder or concomitant disorders has not been explored.

Objectives: The goal of this study was to systematically examine the interactions of ID, ASD, and epilepsy in an adult population through a detailed exploration of the characteristics which these disorders present in the areas of psychopathology, behavior problems, and impaired social behavior. Assessments of psychopathology, behavior problems, and social behavior were made with the ASD-Comorbidity-Adult Version and ASD-Behavior Problems-Adult Version batteries and the Matson Evaluation of Social Skills for Individuals with Severe Retardation.

Methods: Participants were residents at two state-run facilities located in the Southeastern region of the. An on-site licensed psychologist diagnosed all ID participants using DSM-IV-TR criteria (APA, 2000). Selection of participants with and without ASD in this study was based on DSM-IV-TR and ICD-10 diagnostic criteria for Autistic Disorder and PDDNOS. Inter-rater agreement within a multidisciplinary team was required in order for a classification of ASD to be made. Diagnosis of epilepsy was made by a licensed neurologist who determined classification of seizure type based on the ILAE criteria, clinical presentation, and available medical information. Ninety-two participants with ID were matched and compared across four groups, ID (n=23), epilepsy (n=23), ASD (n=23), and combined ASD and epilepsy (n=23). Participants’ ages ranged from 27-78 years (mean=47.75 years, SD= 11.02 years). There were 56 males and 36 females with moderate (n=2), profound (n=88), and unspecified (n=2) ID.

Results: When controlling for age, gender, race, and level of ID, no significant differences were found across groups on measures of psychopathology. However, significant differences were found across groups on measures of behavior problems (p<.02) and social skills (p<.001). The ASD group was significantly more likely to exhibit stereotypy than the epilepsy (p<.004) and ID (p<.002) group. On measures of social behavior, the ID (p<.02) and epilepsy (p<.04) group had significantly more positive verbal behavior than the combined ASD and epilepsy group. The ID (p<.001) and epilepsy (p<.001) group had significantly more constructive nonverbal behavior than the combined ASD and epilepsy group. Lastly, the ID group had significantly more positive general aspects of behavior than the ASD (p<.01) and combined ASD and epilepsy (p<.001) group.

Conclusions: These data suggest that there are critical significant differences among ID participants expressing ID alone or ID and epilepsy from those with comorbid ASD. Specifically, individuals with ASD and combined ASD and epilepsy differ significantly on scales of stereotypy and pro-social behavior. Implications of these findings elucidate the nature and impact of these disorders.