As datasets get larger, risk prediction will improve as will our ability to characterize the balance and effects of common and rare risk variation. We conjecture that the liability arising from common and rare risk variation likely combines additively to determine risk for individuals diagnosed with OCD, similar to the risk patterns for ASD (36, 37). This knowledge can be translated into a deeper etiological understanding of OCD subtypes and their treatment and, in the future, at better predictors of OCD risk. OCD is a clinically and etiologically heterogeneous condition (38) with a complex symptom structure (39). Studies suggest that the burden of common risk alleles of OCD may differ based on OCD symptom type. For example, although not yet replicated, in one study compulsive symptoms rather than obsessive symptoms showed higher SNP heritability and genetic correlations with OCD (40). However, it is still unclear to what extent rare genetic variation, and the joint effect with common variation, differs between the subtypes of OCD, and how this balance may depend on age of onset and sex. Such findings could encourage
