Twin and family studies have shown that people with first-degree relatives (parent, sibling, or child) who have OCD are at a higher risk for developing OCD themselves. The risk is higher if the first-degree relative developed OCD as a child or teen. Ongoing research continues to explore the connection between genetics and OCD .

Imaging studies have shown differences in the frontal cortex and subcortical structures of the brain in patients with OCD. There appears to be a connection between the OCD symptoms and abnormalities in certain areas of the brain, but that connection is not clear. Research is still underway. Understanding the causes will help determine personalized treatments to treat OCD.

An association between childhood trauma and obsessive-compulsive symptoms has been reported in some studies. More research is needed to understand this relationship better. In some cases, children may develop OCD or OCD symptoms following a streptococcal infection—this is called Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections (PANDAS)