Obsessive-compulsive disorder (OCD) is a chronic psychiatric illness that affects 1–3% of the population1 and is characterized by obsessions and compulsions that vary in type and severity, and over time. OCD is responsible for profound personal and societal costs2, including increased risk of suicide3 and overall mortality4. OCD is moderately heritable; twin-based heritability estimates range between 27–47% in adults and between 45–65% in children5–8, with SNP-based heritability estimates between 28–37%9–11.
