Multiple genetic variations can predict depression collectively

For nearly a decade, researchers have studied how single genes contribute to an individual’s risk for depression. A new study, however, looks at how five different common genetic variations related to the serotonin system, combined with interpersonal stress, might be able to predict depression.

“It has the potential to help us understand pathways to depression more thoroughly,” said UNCG Assistant Professor Suzanne Vrshek-Schallhorn. “We also want to work toward being able to detect those who are at the highest risk.”

Ultimately, work that builds from this study may be able to support development of new antidepressants and depression treatments and could eventually allow a psychologist or family doctor to intervene and reach high-risk individuals before depression sets in.

Vrshek-Schallhorn and researchers from the Williams College, Northwestern University and University of California – Los Angeles, followed two samples of adolescents to see how five different genetic variations work together to predict depression if triggered by interpersonal stress. Interpersonal stress could be the death of a loved one, a significant romantic breakup or a loved one’s cancer diagnosis, or any event that impacts the number or quality of relationships in one’s life.

“The innovation is that we’ve looked at these different genetic variations collectively,” Vrshek-Schallhorn said.

The research, she added, shows the collective effect of different markers working together.

As hypothesized, the researchers found that across both samples, those with higher-risk gene factors were more likely to become depressed if the individual went through an interpersonal stress event.

“But it’s more complex than we initially predicted,” she added.

Those same genetic markers that raised the likelihood of depression if triggered by stress also lowered the likelihood of depression under less stressful circumstances. It appears that these genetic variations are simply sensitive to the environment. Under better conditions, the genetic markers are more beneficial to those who have them.

“The protective finding falls in line with other research that shows that some genetic variations confer greater sensitivity to one’s circumstances, regardless whether they are good or bad,” Vrshek-Schallhorn said. “To illustrate this notion, others have used an analogy of the orchid and the dandelion. The orchid thrives with good circumstances, but also struggles in poor circumstances. The dandelion ‘gets by’ regardless of its circumstances.”

The full study, titled “Additive Genetic Risk from Five Serotonin System Polymorphisms Interacts with Interpersonal Stress to Predict Depression,” will be included in the November 2015 issue of Journal of Abnormal Psychology.

Vrshek-Schallhorn, along with Catherine (Kate) B. Stroud of Williams College; Susan Mineka, Richard Zinbarg, Emma K. Adam and Eva E. Redei and Northwestern University; and Constance Hammen and Michelle G. Craske of the University of California, Los Angeles, contributed to the study and paper.

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