Previous research has found that an unhealthy lifestyle can influence depression risk by increasing inflammation.fizkes/iStockPhoto / Getty Images
There’s increasing interest in how lifestyle factors, traditionally linked to physical health, may also be related to mental health.
Eating a healthy diet, being physically active, getting proper sleep and not smoking, for example, have all been tied to a lower risk of depression.
Now, new study findings add to growing evidence that healthy lifestyle habits help guard against depression. And the more of them you engage in, the greater the protection.
The latest research
The study, published online Sept. 11 in the journal Nature Mental Health, aimed to investigate the combined effect of a range of lifestyle factors on the risk of depression.
To do so, an international team of researchers examined data from 287,282 UK BioBank participants, including 13,000 who had depression. Individuals were followed for nine years.
The UK Biobank is a large-scale biomedical database and research resource that includes genetic, brain imaging, physical and lifestyle information collected from 500,000 individuals across the United Kingdom.
The researchers identified seven healthy lifestyle factors associated with a lower risk of depression – healthy diet, regular physical activity (150 minutes of moderate physical activity a week), healthy sleep (seven to nine hours a night), moderate alcohol consumption, never smoking, low-to-moderate sedentary behaviour (less than four hours a day) and frequent social connection.
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A healthy diet was defined as consuming at least four of seven food groups: fruits (at least three servings a day), vegetables (at least three servings a day), fish (at least twice weekly), processed meats (no more than one serving a week), unprocessed red meat (no more than 1.5 servings a week), whole grains (at least three servings a day) and refined grains (no more than 1.5 servings a day).
Among these seven lifestyle factors, healthy sleep offered the strongest protection against depression. Compared to people who didn’t get seven to nine hours a night, those who did were 22 per cent less likely to have depression, including single depressive episodes and treatment-resistant depression.
As for recurrent depression, frequent social connection was the most protective lifestyle factor.
‘Favourable’ lifestyle strongly protective
To examine the combined effect of lifestyle factors on depression risk, the researchers scored participants (zero to seven) based on the number of healthy lifestyle habits they followed.
Participants were then assigned to one of three groups: favourable (score of five to seven), intermediate (two to four) or unfavourable (zero to one) lifestyle.
Compared to people with an unfavourable lifestyle, those with a favourable and intermediate lifestyle had a 57 and 41 per cent lower risk of depression, respectfully.
The findings also revealed that a favourable lifestyle played a strong protective role regardless of a person’s genetic risk for depression.
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The possible ways in which lifestyle factors can influence the risk of depression are complex and dependent on many factors.
After examining the MRI brain scans of 32,839 participants, the researchers found that higher lifestyle scores were correlated with larger brain volumes in a number of brain regions. These larger brain structures were associated with a lower risk of depressive symptoms.
Participants’ blood biochemistry was also assessed. Certain blood markers were identified that suggest an unfavourable lifestyle affects the immune system and metabolism, which in turn can increase the risk of depression.
Previous research has found that an unhealthy lifestyle can influence depression risk by increasing inflammation. Regular exercise, a Mediterranean diet, optimal sleep and quitting smoking have all been shown to have anti-inflammatory effects.
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Experimental evidence has also demonstrated that feeding healthy volunteers meals high in saturated fat and refined carbohydrates increased depressive symptoms and inflammatory blood markers.
A sedentary lifestyle may increase the risk of depression by suppressing the body’s stress response. Psychological stress is associated with heightened inflammation in the body.
Unhealthy lifestyle choices can also lead to the development of obesity, Type 2 diabetes and cardiovascular disease, chronic diseases which themselves can negatively affect mental health.
Takeaways
This new study is not without limitations, including the use of self-report questionnaires to assess lifestyle, which can be prone to error.
Among the study’s strong points is its large sample size. As well, the researchers defined healthy lifestyle factors based on validated national guidelines.
Finally, the study was able to identify underlying ways in which lifestyle factors may protect against depression by assessing the relationship between lifestyle, genetics, brain structure and blood biochemistry.
The present findings strongly suggest that modifying lifestyle behaviours can play a protective role against depression. Just as a healthy lifestyle is important for our physical health, it’s also important for our mental health.
Leslie Beck, a Toronto-based private practice dietitian, is director of food and nutrition at Medcan. Follow her on Twitter @LeslieBeckRD