Depression Risk in the Genes

(Ivanhoe Newswire) -- Why do some people become depressed after a stressful event while others don’t? New research suggests it could be a specific version of a gene.

Researchers from Wisconsin and London followed more than 800 participants from birth into adulthood. Seventeen percent of the participants carried two copies of a short version of the serotonin transporter gene, about 30 percent carried two copies of a long version of the gene, and about 50 percent carried one copy of each version of the gene.

Results of the study show more than 40 percent of the participants carrying two short genes suffered from depression following a traumatic life event. Less than 20 percent of those with long genes developed depression after a stressful event. Researchers define a “stressful event” as losing a job, having a loved-one die, being diagnosed with a serious illness, or experiencing a break-up or divorce.

Terrie Moffitt, Ph.D., from the University of Wisconsin and King’s College in London, says, “We found the connection [between the gene version and depression] because we looked at the study members’ stress history.”

Everyone inherits two copies of the serotonin transporter gene, one copy from each parent. Each version of the gene functions differently. The short version makes less protein, resulting in increased levels of serotonin. Researchers say this may be why it appears less efficient at stopping unwanted messages.

Participants with the short genes who had experienced four or more life stresses accounted for nearly one quarter of the cases of depression. Among those with four or more life stresses who developed depression, more than 40 percent had two copies of the short gene compared to 17 percent with two copies of the long version of the gene.

Researchers say more research is needed to confirm their findings.

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SOURCE: Science, 2003;301:386-389