For lots of people, the New Year means taking up running or joining a gym in the hope that this will help them shed the kilos they’ve piled on over Christmas and the long months of COVID that came before.
I won’t be joining them, because I hate the gym and I find that going for a run is nothing but pain, followed by relief when I stop. But I will continue to do brisk walks outdoors and sessions on my bike because I know they’re good for my overall health and may also cut my chances of developing depression.
A few years ago I saw a study in the journal JAMA Psychiatry where researchers from Massachusetts General Hospital in the US analysed the health records of nearly 8,000 volunteers for a project called the Partners Healthcare Biobank. When they were first enrolled they were genetically tested, and also filled in a survey about their lifestyle habits, which included their level of physical activity.
The researchers found that, over time, people who had a higher genetic risk of depression were indeed more likely to become depressed. But the people who were more physically active, whether they had the higher genetic risk or not, were far less likely to develop the condition compared with those who were less active.
The researchers calculated that doing four hours of exercise each week (that is about 35 minutes a day) cuts your risk of becoming depressed by about 17 per cent. And that’s regardless of genetic status. The researchers didn’t go into why they thought this might be happening, but I wondered when I first read it if at least some of the volunteers were getting a surge in their endocannabinoids, which can contribute to ‘runner’s high’.
Endocannabinoids are naturally occurring substances produced by your body that are known to have a major impact on sleep, appetite, pain, memory and mood.
A couple of years ago, for the BBC series Trust Me, I’m A Doctor, I took part in an experiment with Prof Saoirse O’Sullivan, from Nottingham University, where we looked at the impact of exercise on endocannabinoids. For our experiment, O’Sullivan and her team measured blood levels of endocannabinoids in a small number of volunteers before and after a 30-minute run. They found that the run did indeed boost their levels for several hours afterwards.
I was particularly struck by one of our participants, who said she suffered from severe depression, and found that one of the best ways to control it was with regular runs.
Sadly, when they tested me, there was no surge at all in my endocannabinoid levels after exercising. Which could explain my aversion to running. Despite that, I will keep exercising, but don’t expect me to smile.
- This article first appeared in issue 372 of BBC Science Focus Magazine – find out how to subscribe here
Read more from Michael Mosley:
- How deep breathing can soothe anxiety, help you sleep and more
- The Mediterranean diet is great for your gut (even if it makes you fart)
- How cold showers could boost your immune system
- Do CBD products really offer health benefits?