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It has long been understood that mood disorders like depression, much like most psychological disorders, are often caused by a combination of genetic and environmental factors. Most likely, there is a nuanced interplay between someone's genetic risk for a disorder and the environmental stressors that trigger it: the more genetically vulnerable you are to a given disorder, the lower the amount of environmental triggers you need for it to come into being, and vice versa.

Now, a new study shows how factors that protect against a disorder may behave differently depending on your level of genetic risk as well. Specifically, this research shows how environmental factors like solid social support can help offset the genetic risk of depression, lending itself to a growing body of evidence that positive social relationships are crucial for mental and physical health, and suggesting that social support may even be the most helpful for those who have a high genetic risk for depression.

The study was led by a team at the University of Michigan whose first author was Jennifer Cleary, M.S., a psychology doctoral student and senior author Srijan Sen, M.D., Ph.D., of the University of Michigan Medical School.

Two groups of people undergoing phases of life traditionally understood to be very stressful were studied: newly minted physicians who were in their most grueling year of training, and adults in later stages of life who were grieving the recent loss of a spouse. Interestingly, both groups tended to have somewhat different changes in their social support during their stressful times. While physicians in their first year of residency may have typically been more isolated from friends and family than they were before, recently bereaved spouses often had an uptick in social support—even if temporary—as friends and family circled around them in order to support them in their grief.

Study participants, who numbered more than 1,000 physicians and more than 400 bereaved spouses, were assessed for their genetic risk of depression using what's called a polygenic risk score, which takes into account small variations in several genes that have been tied to the risk of depression. Social support was assessed using self-report measures.

In both groups, depression significantly increased during stressful times. But a striking interaction between social support and genetic risk for depression was found. Specifically, those who had a higher genetic risk for depression had higher rates of depression after losing social support but also lower rates of depression when social support was gained, even as compared to those with a lower genetic risk for depression.

This suggests that when people carry a biological predisposition toward depression, it is anything but a guarantee that they will develop it—and, in fact, they can be most helped by the environmental factor of social support.

Though this study was correlational in nature, meaning that we can't be certain that social support was the cause of the lowered depression, or the sole cause, the association was striking. And though further research is needed to solidify this potential causation, the research suggests two important ideas: that those with high genetic risk for depression may also get greater gains from those factors that protect against it, and that social support in stressful times can potentially have tremendous beneficial effects—even for those thought to be genetically "destined" for depression.

Both notions bring a lot of hope, especially in a time of increased self-reported depression, stress, and loneliness.