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In the United States, around 17.3 million adults had at least one major depressive episode in 2017, according to the National Institute of Mental Health.
Globally, the World Health Organization (WHO) say depression is a leading cause of disability, and estimate more than 264 million people suffer from the condition.
Therefore, a major priority is to identify environmental and lifestyle factors that people can change to reduce their risk of developing the condition.
Now, researchers at Massachusetts General Hospital in Boston have become the latest team to attempt this. They analyzed data on more than 100,000 participants in the UK Biobank, a research program that has been monitoring the health and wellbeing of half a million volunteers in the United Kingdom since 2006.
“Our study provides the most comprehensive picture to date of modifiable factors that could impact depression risk,” says lead author Karmel Choi, Ph.D., a psychiatry researcher at Massachusetts General Hospital and the Harvard T.H. Chan School of Public Health.
Choi and her colleagues focused on 106 modifiable factors that might affect people’s risk of depression. These fell into three categories:
- Lifestyle, including exercise, sleep patterns, media use, and diet.
- Social, including support networks and social engagement.
- Environmental, including pollution and access to green spaces.
The researchers first singled out participants who were already at risk of depression due to their genetics or trauma in their childhood.
They then carried out an “exposure-wide association scan” of the database to identify which of the 106 modifiable factors were associated with the development of depression during the follow-up period.
Finally, they used a statistical technique called Mendelian randomization to further narrow the field to factors most likely to have caused or prevented depression in participants, rather than simply correlating with it.
Mendelian randomization assumes the random inheritance of specific genes, such as those that influence a person’s risk of depression. It uses this to determine how likely it is that other factors have caused a disease or problem.
From this, several modifiable factors appear to protect against depression.
“Far and away the most prominent of these factors was the frequency of confiding in others, but also visits with family and friends, all of which highlights the important protective effect of social connection and social cohesion,” says senior author Jordan Smoller, MD, a psychiatry researcher at Massachusetts General Hospital.
“These factors are more relevant now than ever at a time of social distancing and separation from friends and family,” he adds.
According to the study, confiding in others appears to reduce the risk of depression by 24%.
Social connection even provides some protection in people who were already at higher risk of depression due to their genetics or early life trauma.
The research is published in The American Journal of Psychiatry.
The study also found daytime napping and spending lots of time watching television appear to increase people’s risk of depression by 34% and 9%, respectively.
However, the scientists note further research is needed to determine whether watching television and napping directly raise the risk of depression, or if they simply reflect someone’s sedentary lifestyle.
Physical exercise is a proven way to prevent and treat depression.
“Depression takes an enormous toll on individuals, families, and society, yet we still know very little about how to prevent it. 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.”
– Jordan Smoller
