Systematic Review: Convergence and Divergence Between Autism Spectrum Disorder and Obsessive-Compulsive Disorder: Genetic, Neuroimaging, and Cognitive Findings.

OBJECTIVE: Autism spectrum disorder (ASD) and obsessive-compulsive disorder (OCD), albeit distinct diagnoses, overlap in presentation and frequently co-occur. However, the relationship between them remains poorly understood. We reviewed comparative studies of ASD and OCD to identify patterns of convergence and divergence across these diagnoses at cognitive, neurobiological, and genetic levels.

METHOD: We searched MEDLINE, Web of Science, and PsycInfo databases. The systematic review was registered on PROSPERO (ID: CRD42023395895). Studies that compared individuals with ASD and OCD regarding cognition, neurobiology, or genetics were included. Articles were screened in 2 phases: (1) for relevancy, and (2) based on exclusion and inclusion criteria. We conducted a qualitative synthesis of the results.

RESULTS: The search yielded 2,009 articles. After excluding irrelevant articles (n = 1,623), including studies examining compulsivity without an OCD scale (n = 71), nonempirical reports (n = 97), nonhuman studies (n = 42), studies that were out of scope (n = 6), duplicates (n = 7), and studies with fewer than 20 participants in any comparator group (n = 111), 50 articles remained and were included in the qualitative synthesis.

CONCLUSION: At a genetic level, ASD and OCD share heritability, but studies of polygenic risk are limited. At a neuroimaging level, both diagnoses are associated with reduced cortical thickness in the temporal lobe, but ASD is specifically associated with increased frontal cortical thickness. At a cognitive level, inflexibility may be characteristic of both conditions, but performance in facial emotion processing and sustained attention may differ. The literature is limited by heterogeneity and reduced focus on quantitative traits. Future studies are needed to clarify these relationships.

PLAIN LANGUAGE SUMMARY: Autism spectrum disorder (ASD) and obsessive-compulsive disorder (OCD) are different diagnoses, but both involve repetitive behavior, and children with ASD are much more likely than neurotypical children to be diagnosed with OCD. But the connection between ASD and OCD is not well understood. This systematic review examined the relationships of ASD and OCD at three levels: genetic, neurobiological, and cognitive. Similarities and differences were identified at all levels, though existing studies have some limitations. Future work is needed to better understand the relationships between these diagnoses.

STUDY REGISTRATION INFORMATION: Comparison of Genetic, Neurobiological, and Cognitive Underpinnings of Autism Spectrum Disorder and Obsessive-Compulsive Disorder: A Systematic Review; https://www.crd.york.ac.uk/PROSPERO/view/CRD42023395895.