What causes obsessive-compulsive disorder (OCD)?

Low levels of serotonin and high levels of dopamine seem to play a role in some cases of obsessive-compulsive disorder (OCD). One study found that 10% to 20% of people with this disorder responded to selective serotonin reuptake inhibitors (SSRIs), which increase serotonin levels in the brain. However, it's unlikely that the serotonin and dopamine systems are solely responsible for OCD, because many patients don't respond favorably to any of the drugs that affect these neurotransmitters. In fact, some become worse.

OCD may be related to a common type of infectious disease -- the group A beta-hemolytic streptococcal infections, which include strep throat and scarlet fever. Antibodies recruited by the immune system to defeat these bacteria can attack the body's own tissues, damaging the heart and inflaming the joints. There are signs that, especially in children, these antibodies can also infiltrate the brain -- the basal ganglia, in particular -- causing what is awkwardly named "pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections," or PANDAS. The symptoms of this controversial diagnosis include obsessive thinking and compulsive behavior.

There is additional evidence that these symptoms can appear soon after a streptococcus infection. In a study of children ages 4 to 13 that compared healthy children with those who had OCD, Tourette syndrome, and tic disorders, researchers found a high rate of strep infections in the three months before symptoms of these conditions appeared. A child who suffered several infections of the group A beta-hemolytic streptococcal type had nearly 14 times the average risk of developing OCD or related disorders in the following year.

In some people, OCD is a complication of encephalitis or a head trauma. In such cases, the disorder can be temporary or permanent. It's also common among adults with other anxiety disorders, major depression, and eating disorders. In children, it may be linked to learning disorders. It's likely that these disorders share many of the same neurobiological roots.
The causes of obsessive compulsive disorder are murky at best, but Wayne Goodman, MD, chairman of the Department of Psychiatry at the Mount Sinai School of Medicine, says one risk factor is family history. Find out more in this video.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.