Factors that affect depression risk

The study suggests that social support can be an important factor in preventing depression. filadendron / E+ via Getty Images

Depression is a common, serious mood disorder. Everyone feels sad or lonely sometimes. But if you have depression, these feelings go on for long periods of time. You may feel hopeless or pessimistic, irritable, or have decreased energy or fatigue. You might stop enjoying your hobbies and normal activities and have difficulty concentrating, remembering things, or making decisions.

Experiencing trauma early in life and having certain genes can put you at higher risk for depression. But there are actions that can help protect against depression, such as eating a healthy diet and getting enough sleep and physical activity.

A research team led by Drs. Karmel W. Choi and Jordan W. Smoller at Massachusetts General Hospital and Harvard University analyzed 106 factors in people’s daily lives to see whether they could find other factors that affect depression risk. The work was funded in part by NIH’s National Institute of Mental Health (NIMH). Results were published on August 14, 2020 in the American Journal of Psychiatry.

The team applied a novel, two-stage approach to identify factors that can affect the risk of developing depression. In the first stage, they screened a wide range of lifestyle and environmental factors for links with depression in more than 112,000 older British adults. They looked at behaviors and social factors that people are able to change, including exercise, sleep, TV and computer use, diet, social activities, and social support. Environmental factors included how much green space and noise or air pollution the people lived around. Depression was assessed in the participants at a follow-up survey about six to eight years later.

The researchers found 18 factors linked with lower chances of depression and 11 with higher chances. Those that showed the greatest protection included confiding in others, sleep duration, engaging in exercises like swimming or cycling, a faster walking pace, being part of a sports club or gym, and eating cereal. Factors that had the highest associations with depression were daytime napping; how much time people spent using the computer, watching television, or a cell phone; and eating a healthy diet inconsistently.

To find out which actions might be most helpful for people at high risk of depression, researchers divided the participants into three groups: those with genetic risk factors for depression; those who experienced early life trauma; and those without these known risk factors for depression.

For people with genetic risk factors for depression, frequency of confiding in others and sleep duration were the most protective. How much time they spent on the computer and how much salt they consumed showed the highest increase in risk for depression.

For those who’d experienced traumatic life events, frequency of confiding in others, engaging in exercises like swimming or cycling, and sleep duration showed the most protective effects. The factor that most increased risk of depression was how much television they watched.

For the second stage of the study, the team used a method called Mendelian randomization to narrow down the list to those factors with a causal connection to depression risk. Confiding in others appeared to have the strongest protective effect on depression across all three groups. Visiting with family and friends also appeared to have a protective effect, suggesting that social interactions may be key to reducing risk of depression. Television use increased risk the most.

“Depression takes an enormous toll on individuals, families, and society, yet we still know very little about how to prevent it,” Smoller says. “We’ve shown that it’s now possible to address these questions of broad public health significance through a large-scale, data-based approach that wasn’t available even a few years ago. We hope this work will motivate further efforts to develop actionable strategies for preventing depression.”

More research is needed to determine how the factors identified in this study might contribute to depression. Controlled clinical trials will be needed to test whether changing these factors can help prevent depression.

—by Tianna Hicklin, Ph.D.