Social Connections Mitigate Genetic Risk for Depression

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New research published earlier this month by Zhao and colleagues in Nature Mental Health reveals that factors which contribute to a healthy lifestyle strongly reduce the risk for depression, with social connections being one of the strongest protectors.

The onset of depression is associated with many factors, which can be behavioral, genetic, neurological, and biological in nature. Because the causes of depression are so varied, so too are the strategies we may use for prevention and treatment. While our genetic and neurological risks for depression are fixed, our behaviors are more easily modifiable. Therefore, Zhao et al. aimed to identify lifestyle factors which could be changed to reduce the risk of depression, as well as the neurobiological mechanisms which might respond to these lifestyle changes.

Methodology

The researchers used a large sample of 287,282 participants from the UK Biobank and assessed the medical records of these individuals over a nine-year period. In addition to medical records, the researchers also tracked lifestyle factors such as smoking, exercise, alcohol use, sleep, diet, sedentary behavior, and social connections. For each lifestyle facet, behaviors were coded as healthy or unhealthy. For example, never smoking, engaging in regular exercise, consuming moderate amounts of alcohol, eating a healthy diet, getting 7-9 hours of sleep per night, and sitting at a computer or watching a screen for 0-4 hours per day were considered “healthy.” Social connections were assessed using the Social Isolation Index which assesses the number of people living in a participant’s household, the frequency of visiting with friends and family members, and participating in social and leisure activities.

Depression diagnoses, brain imaging, and genetic information were obtained through medical records with the participants’ consent. The average age of respondents was 57 years old and 50.7% of respondents identified as female. Of the 287,282 participants, 12,916 (4.5%) were diagnosed with a depressive event at least once during the nine-year period of the study.

Results

The researchers found that each of the seven lifestyle factors independently reduced the risk for depression. Healthy sleep had the strongest protective effect on depression (reducing the risk by 22%), followed by never smoking (20%), and social connections (18%). Regular exercise, (14%), less sedentary behavior (13%), moderate alcohol consumption (11%), and a healthy diet (6%) also substantially reduced the risk for depression. Furthermore, although healthy sleep had the strongest impact on preventing a single depression diagnosis, strong social connections had the strongest impact on preventing recurrent episodes of depression. Combining healthy lifestyle factors together further reduced the risk for depression.

Importantly, a healthy lifestyle decreased the risk for depression even when controlling for an individual’s genetic predisposition for depression. Although participants with low genetic risk and more favorable lifestyles showed the greatest decreases in depression diagnoses, those “participants with high genetic risk but favorable lifestyle had a lower risk of depression than those with intermediate or low genetic risk but unfavorable lifestyle.”

The brain imaging results indicated that a healthier lifestyle was associated with larger brain volume “in cortical structures such as the superior prefrontal cortex, orbitofrontal cortex, precentral cortex and insula, and subcortical structures including the pallidum, thalamus, amygdala, and hippocampus…which might suggest improved cognitive control and emotion regulation.”

Limitations

The authors noted that in the current study lifestyle factors were assessed via self-report, rather than more objective measurements such as actigraphy data. The authors also acknowledged that the sample did not include many participants who were from ethnic minority groups and that the participants involved in the study tended to be healthier than the general population.

Conclusions

The authors concluded that “favorable lifestyle plays a strongly protective role in the prevention of depression across a population with different polygenetic risk.” Furthermore, the authors noted that a healthy lifestyle encourages both physical and neurological health. The authors recommend a healthy lifestyle including an optimal amount of sleep and frequent social connection to help prevent depression.