The 2003 findings were heralded far and wide, despite the fact that they had not been verified by other research.
"For an initial study that hadn't been replicated, it was published to much acclaim," Merikangas said. "If it had been replicated, it was an important finding [but] geneticists have been uniformly skeptical from the beginning."
Mental health professionals have been less skeptical, maybe because, Young pointed out, "it was really the first time that people had seen a gene-environment interaction."
Merikangas and her team conducted a "meta-analysis" of 14 existing studies involving 14,250 participants, 1,769 with depression and 12,481 without the disease.
People with previous stressful life events had a 41 percent increased chance of developing depression, but the analysis turned up no association between stressful events and this gene mutation, either in men or women.
"I was surprised by this [but] I haven't give up yet on this particular allele [mutation] as having an effect. It just may be that it's not as big an effect as we thought," said Young, who's also with the VA Center of Excellence for Research on Returning War Veterans at Central Texas Veterans Health Care System.
Young has conducted two experiments, both of which showed that this mutation had an effect on brain structure. But it's still difficult to untangle how this effect arose.
The authors of the new study warned that a research strategy that tries to tie genes with environmental factors may be fraught with danger, but that scientists should be looking at both environmental and genetic factors in trying to account for mental illness.
"We have to work in both directions," Merikangas said.
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