In summary, while comorbidities are often seen clinically and are the most common management currency for clinicians, they have not been consistently considered in phenomenology and etiology studies. Taken together, our results extend the previously reported heritability analyses based on latent classes in TS families, now examining parent-offspring concordance for OCD and ADHD and genetic and environmental correlations between individual diagnoses35. While further research is clearly needed into the complex relationships, both genetic and environmental, between TS, OCD, and ADHD, for the present, our studies suggest that in genetic studies of TS, OCD could also be appropriately considered as a relevant phenotype, (either as an alternate phenotype or as a more genetically homogenous subgroup within the TS phenotype) while ADHD should not. Similarly, clinicians should be aware that TS and OCD share genetic susceptibility factors, and thus that offspring of TS families may be at increased risk for either TS or OCD or for the combination.
