University of Michigan Health System researchers say that genes determine susceptibility to depression. Their findings challenge a 2009 study that called the genetic link into question and add support to previous research that revealed this link.
In 2003, scientists reported that they had discovered a connection between a gene that regulates the neurotransmitter serotonin and an individual’s ability to rebound from serious emotional trauma such as childhood physical or sexual abuse. In 2009, however, the research was called into question by investigators who examined results from 14 studies.
For their research the U-M team examined 54 studies dating from 2001 to 2010 and encompassing nearly 41,000 participants. Details of their analysis are published in the online edition of the Archives of General Psychiatry in a paper titled “The Serotonin Transporter Promoter Variant (5-HTTLPR), Stress, and Depression Meta-analysis Revisited.”
Srijan Sen, M.D., Ph.D, an assistant professor of psychiatry at the University of Michigan Medical School, says, “When we included all the relevant studies, we found that an individual’s genetic make-up does make a difference in how he or she responds to stress.”
When the U-M team restricted their analysis to the 14 studies included in the 2009 JAMA paper, they failed to find a genetic link. The scientists note that this suggests that the scope of the analysis, not the methodology, was responsible for the new findings.
The U-M analysis supports previous findings that individuals who had a short allele of the serotonin transporter promoter polymorphism 5-HTTLPR had a harder time bouncing back from trauma than those with long alleles. In particular, the U-M analysis found robust support for the link between sensitivity to stress and a short allele in those who had been mistreated as children and in people suffering with specific, severe medical conditions.
Only a marginal relationship was found in those who had undergone stressful life events. For instance, Dr. Sen explains, there is no reason to think that the effects of divorce at a biological level would be similar to the effects of losing your home or being physically assaulted.
Dr. Sen cautions that additional susceptibility from having a short allele is only one factor among many that determine how an individual responds to stress. Additional research will help to map an individual’s genetic profile for depression.
“This brings us one step closer to being able to identify individuals who might benefit from early interventions or to tailor treatments to specific individuals,” Dr. Sen notes.