Reaching out to support a person when they're under stress is always a good idea. But a new study suggests that support could be especially important for someone whose genetic makeup makes them more likely to develop depression.

The study shows the importance of social support in buffering the risk of developing depression symptoms in general, using data from two very different groups of people under stress: new doctors in the most intense year of training, and older adults whose spouses recently died. But the largest effect was seen in those who had the most genetic variation that raised the risk of depression.

The paper uses a measure of genetic risk called a polygenic risk score, which is based on decades of research about what tiny variations in specific genes are linked to depression risk.

Compared to individuals in the study who had low depression polygenic risk scores, the doctors and widows with higher risk scores had higher rates of depression after they lost social support, but also had lower rates of depression when they gained social support during stressful times.

The study, published in the American Journal of Psychiatry by a University of Michigan team, suggests that more could be done to target social support to those who can most benefit.

"Our data show wide variability in the level of social support individuals received during these stressful times, and how it changed over time," said first author Jennifer Cleary, M.S., a psychology doctoral student at U-M who is doing her research with senior author Srijan Sen, M.D., PhD, of the U-M Medical School.

"We hope these findings, which incorporate genetic risk scores as well as measures of social support and depressive symptoms, illuminate the gene-environment interactions and specifically the importance of social connection in depression risk."

Sen, who is the director of the Eisenberg Family Depression Center and a professor of psychiatry and neuroscience, adds that even as genetic research reveals more of the DNA variation related to depression vulnerability, learning how that variation leads to depression is crucial.

"Further understanding the different genetic profiles associated with sensitivity to loss of social support, insufficient sleep, excessive work stress and other risk factors could help us develop personalised guidance for depression prevention," he said.

"In the meantime, these findings reaffirm how important social connections, social support and individual sensitivity to the social environment are as factors in well-being and preventing depression."

The new study used data from two long-term studies that both capture genetic, mood, environmental and other data from populations of participating individuals.

One is the Intern Health Study, which enrols first-year medical residents (also called interns) around the United States and beyond, and which Sen directs.

The data for the new paper came from 1,011 interns training at hospitals across the country, nearly half of whom were female, and from 435 recently widowed individuals, 71 pc of them women, who had data available from surveys conducted before and after their spouses died.

In the interns, as Sen and his team have shown in previous work, depressive symptoms increased dramatically (126 pc) during the stressful year of training that includes long and irregular work hours -- often in environments far from friends and family.

In the widows and widowers, depressive symptoms increased by 34 pc over their pre-widowhood scores. This correlates with past research showing loss of a spouse can be one of the biggest stressors in a person's life, Cleary said.