Exercise and mental health

ecently, I have had several friends suffer through mental health issues and made me wonder and dig a bit deeper into the benefits that exercise provides for such circumstances. In Australia, around one million people have depression while one in five between the ages of 16-85 experience a mental illness in any year.

Traditionally, medication and psychotherapy have been the main forms of treatment for issues such as anxiety, depression, or stress (which has its benefits), however exercise has also been shown to be a great treatment option and is continually gaining momentum through research, news outlets, social media, etc.

Mechanisms

Physical activity/exercise brings about several physiological, psychological, and immunological changes as shown in the below diagram. For the purpose of this blog we will elaborate on one mechanism from each.

Endorphin Hypothesis

The main function of endorphins is to aid the body in times of prolonged pain and stress. A common feeling reported by athletes is the “runners high” where a feeling of euphoria is experienced during exercise. The endorphin hypothesis predicts that exercise has a positive effect on depression due to an increased release of endorphins following exercise which are related to a positive mood and an enhanced sense of well-being (Craft and Perna, 2004). In fact, it has been shown that just 20-40 minutes of aerobic exercise can improve anxiety and mood for several hours afterwards (Paluska and Schwenk, 2000).

Distraction hypothesis

Distracting oneself from negative and worrying thoughts is a technique used to help cope with depression. The distraction hypothesis suggests that rather than the physiological change produced by exercise, the effort and physicality of the exercise task itself is enough to elicit a mental “time out”. This theory was first tested about 40 years ago where a study was undertaken on three groups, each given a different mental “time out” being exercise, meditation, and resting quietly in a chair. Each group showed similar reductions in anxiety and stress, suggesting the distraction hypothesis contributes to improved mental health (Bahrke and Morgan, 1978).

Exercise and cytokines

Cytokines are secreted proteins released by cells of the immune system. Chronic inflammation caused by cytokines has been identified as a contributor to depression and poor mental health and there is increasing evidence that the immune system plays a vital role in the development of mental health disorders. There are anti and pro-inflammatory cytokines in the immune system that interact which is beyond the scope of this blog, however what we do know is that exercise has an anti-inflammatory effect which may be attributed to one of the mechanisms being a change in cytokine release in the immune system. A recent study by Paolucci et al., (2018) suggested that moderate intensity exercise may be optimal in improving mental health by decreasing TNF-a which is a pro-inflammatory cytokine.

Type of exercise

In terms of improving mental health and well-being, the mode of exercise may not be necessarily important. Aerobic exercise has traditionally been the most researched type of exercise because of its practicality, however resistance training, yoga, pilates and so on is also proven to be of benefit. In the largest and most extensive study of its kind, an analysis of 33,908 Norwegian adults over 11 years had their levels of exercise and symptoms of anxiety and depression measured. It was found that 12% of cases of depression could have been prevented with just one hour of any exercise per week.

References

• Bahrke M and Morgan W (1978) Anxiety reduction following exercise and meditation. Cognitive Therapy and Research, 2(4), 323-333.
• Craft L and Perna F (2004) The benefits of exercise for the clinically depressed. The Primary Care Companion to The Journal of Clinical Psychiatry, 06(03), 104-111.
• Harvey S, Øverland S and Hatch S et al. (2018) Exercise and the Prevention of Depression: Results of the HUNT Cohort Study. American Journal of Psychiatry, 175(1), 28-36.
• Paluska S and Schwenk T (2000) Physical activity and mental health. Sports Medicine, 29(3), 167-180.
• Paolucci E, Loukov D and Bowdish D et al. (2018) Exercise reduces depression and inflammation but intensity matters. Biological Psychology, 133, 79-84.