14 DAY TRIAL // The whole fad was started by a 2003 scientific study, which held that there must be a gene variant that made some people sail through life all depressed and sad, while others did so without any kind of second thoughts, and always enjoying the moment. The theory seemed solid, because it would have explained some differences between groups of people that were and are still very difficult for scientists to sort out. However, a recent investigation failed to find evidence of the gene variant.
In the 2003 research, published in the journal Science, scientists focused their efforts on the brain chemical serotonin, which seems to, indeed, play a role in the onset of depression symptoms in most people. The investigation revealed that, if people had the short version (allele) of the serotonin transporter gene, they were more likely to become depressive.
The substance is currently one of the main targets of existing or planned anti-depression drugs. The study was, at the time, conducted on 847 people, and was led by Psychologist Avshalom Caspi, now at the Duke University in Durham, North Carolina, ScienceNow informs.
“Everybody was excited about this at the time. It was very widely embraced,” National Institute of Mental Health Genetic Epidemiologist Kathleen Merikangas, from the institution's headquarters in Bethseda, Maryland, explains now. She has been one of the leaders of the new research, together with University of California in San Francisco (UCSF) Geneticist Neil Rish. The team led by the two looked at the 2003 research, and also analyzed 13 other studies that came after it, searching for signs to validate them, or for the alleged gene variant itself.
Reporting in the June 16th issue of the prestigious Journal of the American Medical Association, the team said that, of the studies they reviewed, only three were able to accurately replicate the finds made by the first one. In all, more than 12,500 individuals were included in the new analysis, and the bottom line is that there seems to be no gene variant that could cause depression in people.
However, Caspi and Terrie Moffit, the co-author of the research that started it all, believe that the new analysis is skewed by the fact that it ignored what they say is a large body of scientific pieces of evidence. They argue that Merikangas and Rish also let aside results obtained in the lab, showing that people with the allele serotonin gene were more prone to experiencing stress in controlled conditions.