Is too much exercise bad for your mental health?

Thursday, August 23, 2018. Author Dr. Haran Sivapalan

Is too much exercise bad for your mental health?

The more exercise the better.

In terms of physical health outcomes, it’s easy to see why many of us may be sceptical of this claim. Excessive exercise can lead to fatigue, overtraining syndrome and an increased risk of injury. Skip those all-important rest days, and your body will soon tell you something is wrong.

When it comes to mental health, however, we might not be so quick to dismiss such a claim. Several studies demonstrate an inverse relationship between physical activity performed in leisure-time and poor mental health outcomes – that is, the more you exercise, the less likely you are to suffer mental illnesses such as depression, anxiety and PTSD (Post-Traumatic Stress Disorder). Moreover, exercise not only cuts your risk of developing illness, but can also be used to treat mental health conditions, in much the same way as a drug or psychological therapy. For example, the majority of studies suggest that exercise, either alone or as part of another therapy, can help to treat mild and moderate depression. 

Furthermore, in randomized controlled trials comparing different ‘dosages’ of exercise, the highest ‘doses’ (i.e. the longest and most frequent amounts of exercise) are found to produce the most favourable outcomes for mental health.  

So, the more exercise, the better your mental health, right?

According to a new study, the largest of its kind to date, the answer seems to be “not necessarily”. In fact, the best mental health benefits seem to be linked to exercise that lasts 30 to 60 minutes per session, 3 to 5 times per week.

What did the study show?

The study, published in the journal Lancet Psychiatry, analysed the data of 1,237,194 people across the USA between 2011 and 2015.  These people were surveyed about their exercise habits over the past month. They were also asked the following question, “Now thinking about your mental health, which includes stress, depression and problems with emotions, for how many days during the past 30 days was your mental health not good?”

As with lots of other things in health and fitness, the relationship between time spent exercising and days of poor mental health wasn’t simple and linear. Rather, it followed a ‘U-shaped’ curve (see diagram).

U shaped curve A simplified version of the U-shaped relationship between exercise duration/frequency and mental health burden.

The U-shaped curve explained

Exercising up to about 30 minutes per session and 3 times per week was linked to fewer days of poor mental health in the previous month. This corresponds to the descending, left-hand limb of the ‘U’ – a region where doing more exercise does seem to bring more mental health benefits.

Keep moving left on the graph, to the bottom-most bend of the ‘U’, and there is an ‘optimal dose’ of exercise that is associated with the fewest days of poor mental health. As mentioned earlier, this optimal dose coincided with exercise sessions between 30 and 60 minutes long and with an exercise frequency of 3-5 times per week.

Doing more exercise than this, however, starts to produce less mental benefits. This corresponds to the ascending, right-hand limb of the ‘U’. Compared to the optimal dose (30-60mins, 3-5 days a week), exercising for more than 90 minutes per session or over 5 times per week, while still good for you, is associated with more days of poor mental health.  

To be clear, doing some exercise is generally better than doing nothing at all!  Overall, those who exercised had 43% fewer days of poor mental health compared to respondents who did no exercise at all. That said, very lengthy exercise sessions, in excess of 3 hours, were linked to poorer mental health.

Am I exercising too much?

The above study's findings may make uneasy reading for some of us. As someone currently in the throes of marathon training, and therefore running for periods way in excess of 60 minutes, should I cut down for the sake of my mental health? If you’re following our Build Muscle Prophecy Plan, and working out more than 5 days a week, should you reign it in for a healthier mind? 

The short is answer is: no - this is not what the study shows.

It’s important to note that this study was an example of a cross-sectional study. This means the researchers looked at a population at a specific point in time. What they didn’t do, however, is follow subjects over a long period and explore whether changes in exercise duration led to changes in mental health. As such, the study was not designed to tease apart causation from correlation. It could easily be the case that people who have poor mental health have a tendency to over- (or under-) exercise. In this scenario, exercising too little or too often may be a symptom of (rather than a contributor to) poor mental health.  

When it comes to the amount and intensity of exercise you do, the most important thing is to listen to your own body. If you’re constantly feeling fatigued, you feel your performance is impaired, or you’re suffering from disturbed sleep and a loss of appetite, then it may be time to take an extra rest day and give your body time to recover.

It’s also imperative to remember that exercise, while helpful, is not a panacea for mental illness. If you are suffering from mental health issues, it is recommended to consult a health professional for appropriate support and treatment.

I hope you enjoyed this blog.  Please read my other articles and let me know if you have any questions.

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