IMPULSIVITY AND COMPULSIVITY: TRANSLATIONAL APPROACHES TO COMPULSIVITY IN AUTISM SPECTRUM DISORDERS

Abstract

abstract Background Restricted and repetitive behaviors in Autism Spectrum Disorder (ASD) are heterogeneous, which has prompted attempts to classify repetitive behaviors into subtypes. We performed a factor analysis of repetitive behaviors in ASD that yielded four factors: obsessions, higher order behaviors, lower order repetitive behaviors, and hoarding. The “insistence on sameness” domain of symptoms is an understudied, yet significant, domain because its severity appears to be positively correlated with quality of life. Behaviors in this domain are manifested in behavioral and cognitive rigidity, likely due to difficulty adapting to change. Although several outcome measures assess compulsivity and repetitive behaviors in ASD, none specifically capture the inflexibility commonly exhibited. We developed the Montefiore-Einstein Rigidity Scales (MERS), a semi-structured interview, which focuses solely on changes in cognitive and behavioral rigidity over the course of time. Methods Factor analysis of repetitive behaviors using both clinician rated scales, the MERS and Yale-Brown Obsessive Compulsive Scale (Y-BOCS), and caregiver rated scales, Repetitive Behavior Scale –Revised (RBS-R) and Social Responsiveness Scale (SRS). Data from these scales was collected during two separate ASD treatment studies of children aged 5 to 17, and adults aged 17 to 35. Results In Study 1 (TSO in Adults with ASD) subjects had significant improvements in cognitive/behavioral flexibility on the MERS; and significant improvements on Y-BOCS Compulsive Behavior subscale; SRS Repetitive Behavior subscale and RBS-R Sameness subscale. The Y-BOCs, SRS and RBS-R did not do an adequate job of capturing behavioral and cognitive rigidity. The Y-BOCS does not capture improvements in rigidity; it focuses on compulsive behaviors commonly exhibited in OCD. The SRS-Repetitive Behavior Subscale assesses stereotypic behaviors and restricted interests. The RBS-R Sameness subscale consists of specific examples of inflexible behaviors and therefore does not tap into many possible rigid behaviors. In Study 2 (Hyperthermia in Children with ASD) subjects had significant improvements on the SRS Repetitive Behavior subscale and RBS-R Compulsive Behavior subscale. Neither the SRS nor the RBS-R did an adequate job of capturing behavioral and cognitive rigidity. The SRS-Repetitive Behavior Subscale assesses stereotypic behaviors and restricted interests, while the RBS-R Compulsive Scale assesses more compulsive behaviors. Conclusion Both studies utilized novel treatment approaches in different age populations and significant improvements in repetitive behaviors were found on treatment versus placebo. Symptoms in the Rigidity-Insistence on Sameness domain emerged as responsive to treatment. This domain appears to be associated with quality of life measures, is linked to gene and chromosomal regions, and there is evidence of familiarity (2-4). We have developed and have refined the MERS to better understand and assess cognitive and behavioral rigidity and inflexibility in ASD, and to help track changes with treatment. The MERS measures 1. Degree of Behavioral Rigidity, 2. Degree of Cognitive Rigidity, 3. Interference associated with rigidity, and 4. Distress associated with Rigidity. Since this domain of symptoms may have a unique neurobiological origin and differential treatment response, we recommended future ASD studies utilize this measure to stratify patients into more homogeneous groups and/or as an outcome measure to track changes in rigid behaviors.