Depression is a burdensome condition affecting approximately one in five of us across our lifetime. In addition to the profound individual impact on our lives, health and wellbeing, it is major contributor to taking time off work and even early death. Whilst genetic predisposition partially contributes, it is estimated, the bulk of the cases of depression are developed due to our experiences and our behaviours (which can protect or make us more susceptible).
One of the lifestyle behaviours we have looked at to protect from depression is physical activity. In a seminal study including over 260,000 people, we found that across all age groups, genders and geographical regions, being more active was associated with 15% less risk of developing depression in the future (in 7.5 years in our study). The greatest protection against depression equating to 30%, was evident when people engaged in 150 minutes of moderate physical activity per week.
What gives further strength to these observational studies are Mendelian randomization studies which have consistently shown that higher physical activity protects against depression, including our own recent study. My favorite study of this kind assessed the physical activity levels of people with genetic increased risk of depression and concluded that physical activity can help prevent new cases of depression.
We have also been interested in can having a higher fitness levels also prevent new cases of depression? In a well-publicized paper including over 1 million adults, we demonstrated that higher levels of cardiorespiratory fitness can protect against future depression in adults. More recently, we sought to understand if cardiorespiratory fitness or muscular strength both had a role in protecting from depression. The answer is that having good heart and muscle strength both appear to play an important role, but the protection offered is greatest when we have good heart and muscle fitness.
In summary, the evidence does suggest that physical activity and fitness can help protect against depression. However, depression is a complex and multifactorial condition – often influenced by multiple factors over time (or sometimes in the short term if there is a traumatic event). So, it is not that simple to say that you can exercise and prevent depression. There will be many people who have several stressful or difficult things happen in their life and no amount of exercise will keep the depression away. However, by being active and keeping ourselves fit, on average we can reduce our risk but not eliminate this completely.
If you are interested in the science and application of exercise for mental health, check out the Courses section.
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