Ten years of data confirm that exercise is a powerful tool against depression

Ten years of data confirm that exercise is a powerful tool against depression

A new onePLOS oneThe study provides an updated review of how exercise affects depression in otherwise healthy adults.

How does physical activity improve mental health?

The World Health Organization (WHO) considers physical inactivity to be the fourth most important risk factor affecting mortality, in addition to its role in increasing the incidence of many non-communicable diseases. Regular physical activity is strongly associated with positive health outcomes, including improved mental health by reducing the risk of anxiety and cognitive impairment.

Mental illnesses such as depression can significantly impact an individual's quality of life. Although cognitive behavioral therapy (CBT) and pharmacological strategies are commonly prescribed to treat mental disorders, these strategies have numerous limitations. For example, pharmacological treatment of depression can result in drug-related side effects such as constipation, headache, diarrhea, insomnia, nausea, and sleepiness, while CBT is associated with moderate effectiveness.

Previously, researchers have reported that over 50% of individuals with depression do not respond to first-line antidepressants, of whom approximately 30% have no improvement in their symptoms with currently available treatments. Given the higher global prevalence of depression and low effectiveness of available treatments, cost-effective treatment of depressive disorders is urgently needed.

About the study

In 2014 the researchers of the youngestPLOS oneThe study published a meta-analysis showing that exercise had a moderate overall effect size (ES) on depression. Here, the overall score of physical exercise for depression was 0.56, which is similar to that of pharmacological or psychotherapeutic treatments for depression.

Relevant studies published after 2014 were obtained from PubMed, CINAHL Complete, Psycinfo, PSYNDEX, SOCINDEX, and SportDiscus databases for meta-analysis to update their previous analysis with more recent data.

Eleven studies met all eligibility criteria and were included in the final meta-analysis. The study included 229 randomized controlled trials (RCTs), controlled trials, cluster RCTs and longitudinal studies with 16,255 participants.

Depression levels were measured using the Hamilton Depression Scale (HAM-D), the Beck Depression Inventory (BDI), and the Hamilton Depression Rating Scale (HAM-D).

Physical activity and exercise as an intervention for the treatment of depression

Over the past decade, researchers have continually reported that both exercise and physical activity can reduce depressive symptoms and improve the quality of life for people with depression. These benefits cannot be attributed to a single, isolated mechanism and are likely due to an interplay of multiple psychological and neurobiological mechanisms.

Although many studies use physical activity and exercise interchangeably, it is important to note that exercise is always physical, but physical activity is not necessarily considered exercise. This is because exercise is more structured and planned, while physical activity includes anything that causes skeletal muscle contraction and results in a significant increase in calorie expenditure compared to energy expenditure.

Recent studies have reported that the effect of physical activity/exercise on depressive symptoms varies depending on type, intensity, and minimum duration. Compared to no intervention, exercise may have a moderate to large impact on alleviating depressive symptoms. Exercise also appears to be more beneficial than usual care, such as placebo pills or waitlist control conditions.

Training relieves depressive symptoms for both men and women. In particular, exercise, psychosocial interventions and relaxation strategies were found to have comparable effects. Nevertheless, existing studies emphasize that the trainer positively influences patients' reactions to treatment.

In particular, aerobic exercise such as swimming, running, jogging and walking had a stronger antidepressant effect than psychological treatments or antidepressants. Moderate-intensity interventions with a shorter weekly duration provided a more beneficial effect than high-intensity interventions.

Neurobiological explanations and future prospects

Depressive disorders arise due to dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis, reduced responsiveness to glucocorticoids, increased secretion of corticotropin release (CRH), and increased size and activity of pituitary glands. Even ten years after their original meta-analysis, the specific neurobiological changes involved in the anti-pressure effects of exercise and physical activity remain unclear.

Researchers have suggested that the effects of exercise and physical activity can be attributed to physiological changes in hypothalamic-pituitary-adrenal axis function, monoamine metabolism, neurotrophic factors and neuroinflammation. These hypotheses are supported by many systemic reviews that have similarly reported the effects of physical activity on the serotonergic system and the HPA axis.

To optimize the antidepressant effects of physical activity, biomarkers of depressive disorders need to be monitored regularly. The optimal dose-response relationship also needs to be determined to provide clinicians with clear guidelines for prescribing this strategy to treat depression symptoms.

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