Causes of OCD Remain a Mystery

Second in a five-part series about children and obsessive-compulsive disorder.

The cause of obsessive-compulsive disorder (OCD) remains elusive. Yet research shows it is an organic disorder, which although it usually begins in childhood is not caused by family problems, bad parenting or attitudes learned at an early age.

Brain imaging studies using positron emission tomography (PET) have compared people with and without OCD. Those with OCD have brain activity different from people with other or no mental illness. These scans also show that behavioral and drug therapy help change biochemistry in the brain.

A genetic component contributes to OCD. However, just because a child may have a genetic predisposition for OCD doesn't mean the disorder will develop. About 20 percent of children with OCD have a relative with OCD, according the Anxiety Disorders Association of America.

In a small number of children suffering from obsessions and compulsive behaviors typical of OCD and tic disorders, symptoms worsen after an infection with strep throat, says Susan E. Swedo, M.D., chief of the Pediatric and Developmental Neuropsychiatry Branch of the National Institute of Mental Health (NIMH) who among others is studying such a possible connection.

Some evidence points to an autoimmune response to the infection in which antibodies attack healthy and infected cells, leading to inflammation in the brain's basal ganglia, an area involving movement and motor control. The syndrome known as Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections (PANDAS) usually occurs in young children and has a dramatic, sudden onset or worsening of symptoms both during and after strep infections. The NIMH is investigating this area.

However, strep-triggered mental disorders are extremely rare. "Strep infection doesn't account for all the cases," says Mark Wellek, M.D., past president of the American Society for Adolescent Psychiatry, says, and treatment remains the same.

Other evidence points to changing hormones as a possible factor, and to further confound researchers, OCD in rare cases can co-exist with tic disorders associated with Tourette's.

"If we do find out what causes it, we hope we can cure it," says Monica Marshall, director of child mental health for the National Mental Health Association.

Learn the signs in part three of a five-part series of children with OCD.

Sources:

Centers for Disease Control and Prevention

The American Society for Adolescent Psychiatry

Anxiety Disorders Association of America

The National Institute of Mental Health

The National Alliance for the Mentally Ill

The American Academy of Child and Adolescent Psychiatry

The American Academy of Pediatrics

The American Academy of Family Physicians

The Obsessive Compulsive Foundation

The Madison Institute of Medicine

This article was reviewed and updated June 2007.