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Gene Mutation Linked to Obsessive Compulsive Disorder
By Cheryl Simon Silver

A rare mutant, malfunctioning gene gleaned from DNA samples of patients with obsessive compulsive disorder (OCD) appears to contribute to this debilitating neurospychiatric disorder in at least some people.

Researchers have found a mutation that appears to cause OCD in members of two unrelated families. obsessive compulsive disorder is one of the 10 leading causes of disability in the world, and affects an estimated seven million people in the United States. People with OCD are plagued by repetitive unwanted thoughts and behaviors.

This is the first instance where a mutation with a functional effect seems so tightly associated with a specific psychiatric disorder. --Dennis Murphy

The number of individuals identified with the mutation is small but the finding is significant, says Dennis Murphy of the National Institutes of Mental Health, who led the study.

“This is the first instance where a mutation with a functional effect seems so tightly associated with a specific psychiatric disorder,” Murphy says.

Murphy's team, which included Norio Ozaki of Jujita Health University School of Medicine in Japan and other scientists, analyzed DNA from 112 unrelated individuals with OCD and 271 patients with other psychiatric disorders or no disorders at all.

From that large group, they found that two unrelated individuals with OCD possess a mutation in the human serotonin transporter gene, hSERT, which increases the transport of serotonin, a chemical neurotransmitter that affects emotions and drives.

The researchers interviewed family members of the two OCD patients with the gene mutation and studied their DNA. Out of 14 family members, seven do not have the mutation and do not have OCD. The individuals who do have OCD also have other conditions including tic disorder, anorexia nervosa, Asperger's syndrome, alcohol problems, social phobia and depression. This observation suggests that the gene mutations are not specific to OCD, the researchers report in Molecular Psychiatry.

The two original patients and their siblings have another change in hSERT. The fact  that the OCD patients  have two changes in the same gene may explain why their illnesses and those of their siblings have been so severe and resistant to treatment.

“I really think that this could be a substantial advance in psychiatry because it may provide a way to identify a specific cause for a psychiatric disorder,” says Julio Licinio, editor of Molecular Psychiatry. Researchers hope to learn whether the mutation, or a similar mutation, could be common in a number of different psychiatric conditions, he adds.

“This may be the tip of an iceberg, but at least we know there's an iceberg,” Licinio says.

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Murphy, D.L. et al. Serotonin transporter missense mutation associated with a complex neurophychiatric phenotype. Molecular Psychiatry. 8, 933-936 (November 2003).


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