Gene More Than Doubles Risk of Depression (cont.)
Although carriers of the short variant who experienced four or more life stresses represented only 10 percent of the study participants, they accounted for nearly one quarter of the 133 cases of depression. Among those with four or more life stresses, 33 percent with either one or two copies of the short variant - and 43 percent of those with two copies of the short variant - developed depression, compared to 17 percent of those with two copies of the long variant.
The stressful life events led to onset of new depression among people with one or two copies of the short gene variant who didn't have depression before the events happened. The events failed to predict a diagnosis of new depression among those with two copies of the long variant. Among those who had experienced multiple stressful events, 11 percent with the short variant thought about or attempted suicide, compared to 4 percent with two copies of the long variant. These self-reports were corroborated by reports from participants' loved ones.
The researchers suggest that effects of genes in complex disorders like psychiatric illnesses are most likely to be uncovered when such life stresses are measured, since a gene's effects may only be expressed, or turned on, in people exposed to the requisite environmental risks.
Also participating in the study were: Karen Sugden, Alan Taylor, Dr. Ian Craig, Joseph McClay, Jonathan Mill, King's College London; Dr. Honalee Harrington, University of Wisconsin; Judy Martin, Dr. Richie Poulton, Dunedin School of Medicine; Dr. Antony Braithwaite, University of Otago.
In addition to NIMH, the research was also supported by the University of
Wisconsin Graduate School, United Kingdom Medical Research Council, Health
Research Council of New Zealand, William T. Grant Foundation, Royal
Society-Wolfson Research Merit Award.
Last Editorial Review: 11/5/2004