Genetic And Phenotypic Overlap Of Specific Obsessive-Compulsive Subtypes With Tourette Syndrome

BackgroundThe unique phenotypic and genetic aspects of obsessive-compulsive (OCD) and attention-deficit/hyperactivity disorder (ADHD) among individuals with Tourette syndrome (TS) have not been well characterized.MethodsOCD and ADHD symptom patterns were identified among patients with TS and their family members (N=3494) using exploratory factor and latent class analyses; clinical associations and heritability of these factors were examined.ResultsFactor analyses yielded 2- and 8-factor models for ADHD and OCD, respectively. Both ADHD factors (inattention and hyperactivity/impulsiveness) were genetically related to TS, ADHD, and OCD; all OCD factors (related to symmetry/contamination, unusual thoughts, aggressive urges, and hoarding) were genetically related to OCD. The OCD aggressive urges factor was genetically associated with TS and ADHD, the symmetry/exactness and fear of harm factors were associated with TS, and the hoarding factor was associated with ADHD. Latent classes based on OCD and ADHD factor sum scores to examine the relationships between OCD and ADHD symptoms in probands and family members revealed a three-class solution: ADHD; OCD+ADHD; and asymmetry/exactness, hoarding, and ADHD. The majority of participants with TS, ADHD, mood, and anxiety disorders, as well as mothers, fathers, and probands, were classified in the ADHD class. In contrast, the largest percentage of participants with OCD and disruptive behavior disorders were classified in the asymmetry/exactness, hoarding, and ADHD class.ConclusionsSymmetry/exactness, aggressive urges, fear of harm, and hoarding show complex genetic relationships with TS, OCD, and ADHD, and transcend diagnostic boundaries, perhaps representing a failure of top-down cognitive control common to all three disorders.