OCD is a common disorder that affects adults, adolescents, and children all over the world. Most people are diagnosed by about age 19, typically with an earlier age of onset in boys than in girls, but onset after age 35 does happen.
The causes of OCD are unknown, but risk factors include:
Twin and family studies have shown that people with first-degree relatives (such as a 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 and may help improve OCD diagnosis and treatment.
Brain Structure and Functioning
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 specific, personalized treatments to treat OCD.
People who have experienced abuse (physical or sexual) in childhood or other trauma are at an increased risk for developing OCD.
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). For more information, please read this fact sheet on PANDAS.