Exclusive reliance on OCD diagnosis and clinic samples may be another reason for slow progress. Diagnoses are useful in clinical practice, but in genetic research, could obscure phenotypic and genetic heterogeneity, hide variation in symptom severity among cases, and miss sub-threshold OCD cases11. Clinical samples are slow and expensive to collect. Alternatively, if OCD represents an extreme of obsessive–compulsive (OC) traits widely distributed in the population, then genetic research could focus on quantitative OC trait measures. A quantitative trait-based measure assesses the full range of OC traits (e.g., from extreme difficulty, to complete ease, discarding useless objects) to capture all their variance, which could boost power for genetic studies11,12, especially in general population samples.
