Common problem with loci presumed to have psychological or behavioral effects, Report on Gene for Depression Is Now Faulted:
The original finding, published in 2003, created a sensation among scientists and the public because it offered the first specific, plausible explanation of why some people bounce back after a stressful life event while others plunge into lasting despair. The new report, by several of the most prominent researchers in the field, does not imply that interactions between genes and life experience are trivial; they are almost certainly fundamental, experts agree. ... Since then, researchers have tried to replicate the gene finding in more than a dozen studies. Some found similar results; others did not. In the new study, being published Wednesday in The Journal of the American Medical Association, Neil Risch of the University of California, San Francisco, and Dr. Merikangas led a coalition of researchers who identified 14 studies that gathered the same kinds of data as the original study. The authors reanalyzed the data and found "no evidence of an association between the serotonin gene and the risk of depression," no matter what people's life experience was, Dr. Merikangas said. By contrast, she said, a major stressful event, like divorce, in itself raised the risk of depression by 40 percent.
This is the lot of genes which are implicated in traits of great interest, such as IQ. Science is naturally provisional, but some science makes better initial copy. Here's the original paper, Influence of Life Stress on Depression: Moderation by a Polymorphism in the 5-HTT Gene:
In a prospective-longitudinal study of a representative birth cohort, we tested why stressful experiences lead to depression in some people but not in others. A functional polymorphism in the promoter region of the serotonin transporter (5-HT T) gene was found to moderate the influence of stressful life events on depression. Individuals with one or two copies of the short allele of the 5-HT T promoter polymorphism exhibited more depressive symptoms, diagnosable depression, and suicidality in relation to stressful life events than individuals homozygous for the long allele. This epidemiological study thus provides evidence of a gene-by-environment interaction, in which an individual's response to environmental insults is moderated by his or her genetic makeup.