March 31, 2006 -- Scientists report that a certain gene variation is nearly twice as common in people with obsessive-compulsive disorder (OCD) as in people without OCD.
The gene variation "exerts a moderate effect on risk of OCD," write Xian-Zhang Hu, MD, PhD, and colleagues in The American Journal of Human Genetics.
But there's more to OCD than a single gene variation. Inheriting that gene variation is "insufficient to produce OCD" by itself, Hu's team notes.
The researchers put their findings in perspective by stating that the gene variation probably has less effect on OCD risk than having a first-degree relative (mother, father, brother, or sister) with OCD.
Hu is a research scientist in the neurogenetics lab of the National Institute on Alcohol Abuse and Alcoholism (NIAAA).
Fourth Most Common Psychiatric Disorder
Hu's study describes OCD as a "chronic and disabling disorder" with these hallmarks:
- Recurrent, intrusive thoughts that cause distress and interfere with function.
- Repetitive behaviors or mental acts performed in response to obsession.
About 2% of the U.S. population has OCD, making OCD the nation's fourth most common psychiatric disorder, the study states.
The exact cause of OCD isn't known. Cognitive behavior therapy and selective serotonin reuptake inhibitor (SSRI) drugs are "partially effective" in treating OCD, write Hu and colleagues.
They studied 169 U.S. whites with OCD and 253 without OCD, looking for genetic patterns in the serotonin transporter (SERT) gene, which SSRIs target.
Gene Variation Stood Out
A particular SERT gene variation was nearly twice as common in people with OCD, Hu's team found.
The researchers got similar results in studying 86 Canadian families in which a child had OCD and the parents didn't have OCD. Among kids with OCD, almost twice as many had the gene variation, the study shows.
The gene variation appears to boost SERT activity, notes David Goldman, MD, chief of the NIAAA's neurogenetics lab, who worked on the study.
"Whereas most genetic diseases are caused by variations that lead to reduced gene function, we found that a common SERT variant that increases SERT activity also increases the risk for OCD," Goldman says in an NIAAA news release.
More work lies ahead, but learning more about the genetics of OCD may one day lead to new OCD treatments, the researchers write.