A Brief Review of Exercise as a Treatment for Depression

1.  Introduction

In this chapter, we will review the evidence base for the effectiveness of different forms of exercise as treatments for clinical depression and related conditions.

The standard care approach for clinical depression is psychotherapy or antidepressant medication, either alone or in combination. Every year, an estimated 30 million Americans are prescribed antidepressant medication, often for prolonged periods. However, antidepressants, like all medicines, have costs and potential undesirable side effects, making the search for cost-effective and tolerable alternatives important for patient care.

There is a strong and growing scientific evidence base for exercise in the treatment of depression itself, and for prevention of depression, reducing anxiety and improving overall well being. Unsurprisingly, inactivity is associated with worse mental health.

2.  Exercise for depression: the evidence

At the time of writing, several thousand research studies have been published on physical activity, exercise, and depression. These studies are of variable quality and therefore importance. Where possible, we have selected articles of the highest quality – i.e., randomized trials — and where not, we have chosen the best from what was available in the published literature, including country guidelines which have undergone extensive peer review.

Highlights from a selection of the most relevant studies and guidelines have demonstrated that exercise is ^1–5:

• Proven to prevent and treat depression
• Effective as a standalone treatment for mild to moderate depression
• Effective as an add-on strategy for both therapy and antidepressant medication treatment for depression
• As effective as psychotherapy or antidepressant medication
• Even at lower levels, physical activity is enough for improving mood
• Associated with higher patient satisfaction and lower numbers of dropouts compared to standard treatments.

How much exercise is enough? The UK’s National Institute for Health and Care Excellence (NICE) recommends that people with mild to moderate depression take part in about 3 sessions a week, lasting about 45 minutes to 1 hour, over 10 to 14 weeks.

How long before the effects are apparent? These same guidelines further suggest exercising for a minimum of 9 -12 weeks, although the optimal time period is unknown. It is also unclear how long it may take for the mental health benefits of exercise to become evident.

Does exercise work for everyone? Naturally, some people may respond positively, others may find it doesn’t improve their mood much, and some may experience only a modest benefit in the short term.

What about side effects? No treatment, including exercise, is without adverse effects and risks. The main adverse effects are physical: muscle soreness, injury, and fatigue. Studies suggest that exercise has far fewer side effects than medication.

Nonetheless, on balance, guidelines and researchers continue to advise that the beneficial effects of exercise on physical and mental health outweigh the risks.

3.  Cardio/AEROBIC EXERCISE for depression

“Cardio” exercise is a broad term referring to any form of exercise increasing the heart rate. Aerobic exercise is any form of exercise that uses oxygen. However, while “aerobic” and “cardio” are used interchangeably, they are technically different while are occurring simultaneously.

Cardiorespiratory fitness is a known protective factor against depression and cardiovascular mortality ⁶. For example, a large 5-year study in the Netherlands found a strong link between higher preexisting cardiorespiratory fitness and lower levels of depressive symptoms: moderate or high fitness halved the risk of developing depressive symptoms. In this study even lower intensity exercise was protective against depressive symptoms ⁷.

Cardio exercise has a strong evidence base for the effective treatment of depression, including in a Cochrane review ⁸ and meta-analysis ². The Cochrane review included 39 trials of exercise in 2,326 people with depression. Overall, the authors found that exercise was beneficial for depression compared with no treatment or other control intervention. However, differences between the studies meant the results were not necessarily robust.

The more recent Morres et al. systematic review and meta-analysis (2019) included 11 high-quality trials of 455 adults with depression, who were both inpatients and outpatients. They found that aerobic exercise had a moderate-to-large effect on depression. Interestingly, similar effects were found in subgroup analyses, including depression severity, use of exercise equipment, individual or in group exercise, and exercise performed in hospital or not.

4 RESISTANCE training for depression

Resistance training improves mood and reduces depressive symptoms. A large study published in JAMA Psychiatry combined the findings of 33 randomized trials of resistance training for depression involving nearly 2,000 subjects ⁹. Resistance training was defined as exercises designed to increase strength, endurance, and muscle mass.

The authors found that people with mild to moderate depression who performed resistance training on two or more days a week saw significant reductions in their depressive symptoms, compared with people who did not. The findings also suggested that resistance exercises may be even more beneficial for those with more severe depressive symptoms. In addition, resistance training elevated patients’ moods, regardless of the frequency of the training, whether they got stronger or not, or their underlying health status.

A subsequent systematic review of supervised resistance training found conflicting results with half of the included studies showing an effect, and the remainder showing no effect on depression or depressive symptoms ¹⁰. The authors recommended further high-quality randomized trials of resistance training for depression.

5.  HIIT (High intensity interval training) for depression

HIIT is an increasingly popular form of exercise involving short bursts of high intensity exercise alternating with rest or low intensity exercise. HIIT improves physical and mental health in healthy people, and in people with various conditions like metabolic and cardiovascular disease. HIIT improves important measures like inflammation, blood pressure, blood glucose, and cardiovascular fitness ¹¹.

Unfortunately, the science to date does not provide a definitive answer on HIIT as a treatment for clinical depression. Results are mixed, despite a positive meta-analysis comparing HIIT with moderate intensity training in patients with severe mental illness, including depression. This study found that both forms of training improved depressive and fitness measures, with only a moderate difference between HIIT and ¹² continuous exercise ¹³.

A recent study during the Pandemic of home-based HIIT versus moderate intensity exercise (for 40 minutes a day on 6 days a week) revealed that both exercises reduced self-rated depression, anxiety, and stress scores ¹⁴.

Overall, HIIT improves physical health measures, but it’s effects on clinical depression are not yet well-established.

6.  ConclusionS

Exercise is an evidence-based option for the treatment of clinical depression. Exercise is also protective against developing depression. It has minimal side effects, is well-tolerated, and is readily available at low cost.

Exercise is included in a number of clinical guidelines for depression and is increasingly being prescribed with other treatments. Current guidelines recommend at least 30 minutes of exercise for three to five days a week.

However, there is insufficient research to match patients to the optimal type, duration, and frequency of exercise for their needs. Given the known positive effects on well being, cardiovascular fitness, and longevity; and the protective effects against mental illness, cancers, and cardiac disease, clinicians should consider exercise prescriptions for depressed patients. Additionally, healthcare systems should be encouraging exercise in the wider population.

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