Study: High-Intensity Exercise Greatly Improves Mental Health in Adults

April 17, 2023

High-intensity physical activity greatly improves mental health symptoms in adults across clinical conditions, according to a meta-analysis recently published in the British Journal of Sports Medicine. Vigorous and short-duration exercises were found to be most effective in improving mild-to-moderate symptoms of depression and anxiety, compared to usual care.¹

Higher-intensity workouts were found to be most effective at improving symptoms of depression and anxiety — the comorbid conditions that most commonly occur alongside ADHD. Short-term interventions lasting 12 weeks or less were more effective at improving symptoms than were longer-term exercise programs. Outcomes were measured through self-reports or clinical assessments.

Healthy adults, adults with mental health disorders, and adults with chronic diseases were included across 97 systematic reviews. The study found mental-health benefits associated with all modes of physical activity, including strength-based exercises; mixed mode exercises; stretching, yoga, and mind-body modalities; and aerobic exercise.

Exercise, Depression & Anxiety

While positive effects spanned all groups, the clinical effects of different modes of physical activity varied. Researchers found that resistance or strength training had the largest beneficial impact on depressive symptoms.

“Physical activity improves depression through various neuromolecular mechanisms including increased expression of neurotrophic factors, increased availability of serotonin and norepinephrine, regulation of hypothalamic–pituitary–adrenal axis activity and reduced systemic inflammation,” the researchers wrote.

For symptoms of anxiety, mind-body modalities like yoga had the greatest impact.

“Physical activity (PA) on depression and anxiety are due to a combination of various psychological, neurophysiological, and social mechanisms,” the researchers said. “Different modes of PA stimulate different physiological and psychosocial effects, and this was supported by our findings.”

High-intensity exercise has also been associated with improvements in sleep — thought to be closely connected to mental health.² For middle-aged or older adults, the long-term effects of too much sleep (more than 8 hours) or too little (less than 6 hours) can lead to death by various causes, including cardiovascular disease. Exercise can help to negate those mortality risks. In a recent U.K.-based population cohort, adults who exercised often greatly lowered their sleep-duration-related mortality risk. That risk was nearly non-existent when adults went beyond the WHO’s recommendation of 150 minutes of moderate to intense physical activity per week.³

In the current study, the adults who benefited most from physical activity included generally healthy adults; pregnant or postpartum women; adults with depression; and adults with HIV or kidney disease. Participants included adults aged 18 and older.

Exercise and ADHD

Exercise was rated very highly by people with ADHD in ADDitude’s treatment survey conducted in 2017. More than half of the 1,563 adult respondents rated exercise as “extremely” or “very” effective in managing their ADHD symptoms — which may coexist with and become exacerbated by symptoms of mood disorders like depression.

Exercise was one of the top-rated treatment options among adults in the survey, but only 17% said that exercise came at the recommendation of their doctor. Though it received lower patient ratings, medication was more often used to treat symptoms; patients said they believed medication would have more “immediate” and “consistent” effects. Though exercise promises to lessen some of the commonly reported side effects of ADHD medication — like sleep disturbances and irritability — only 37% of ADDitude survey respondents said physical activity was included in their treatment plan.

The current meta-analysis found that “effect size reductions in symptoms of depression (−0.43) and anxiety (−0.42) are comparable to or slightly greater than the effects observed for psychotherapy and pharmacotherapy.”

Limitations & Future Research

The growing body of research on exercise and mental health is promising, but not without its flaws.

Though researchers from the present analysis “applied stringent criteria regarding the design of the component randomized controlled trials to ensure that effects could be confidently attributed to PA,” AMSTAR 2 ratings were a limitation. Of the 97 systematic reviews, 77 received a clinically low score. Those studies were identified as having more than one critical flaw, and three or more non-critical weaknesses.

A meta-analysis published in Nature found many short trial durations, small sample sizes, variable outcome measures, and other potential biases or inconsistencies in studying exercise and cognition.^{4 5} That’s not to say exercise is without cognitive (or social, or physical) benefits, but the research on mental health and exercise requires more validation.

“Organizations committed to public health, such as the World Health Organization or the National Institutes of Health, currently recommend regular exercise as a means to maintain a healthy cognitive state, which based on our findings cannot be affirmed,” they wrote.

The current study acknowledges this, stating: “Patient resistance, the difficulty of prescribing and monitoring PA in clinical settings, as well as the huge volume of largely incommensurable studies, have probably impeded a wider take-up in practice.”

Future research should reflect these limitations and consider ways to integrate conclusive findings into the clinician-patient setting.

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