Summary: moderate exercise interventions are not only preventative, but have now been shown to actively treat depressive symptoms, and should be accepted as an evidence-based treatment method within psychological care. This could help ease the massive strain on global mental health infrastructure.
It all started with an Instagram reel.
It was early 2023 and I was depressed and scrolling. I came across a video that said: the act of contracting your muscles releases a hormone associated with hope. Honestly, I thought it was BS. I have a degree in clinical psychology, and have struggled with depression for 8 years - it’s just not that easy. I passed it off as social media blowing up a dodgy research finding to get views.
Eureka on the Treadmill
But the idea just wouldn’t let me go. It nagged at me. A month later, to test it out, I signed up for my first ever gym membership. The results blew me away. For years I’ve tried psychotherapy, CBT, medications, ADHD training — but none of those had as fast and as reliable an effect on my thoughts as exercise. Running for 5 minutes, the negative thoughts were gone. After 10, they had magically been replaced by positive thoughts. This was a radical, highly unexpected outcome.
The Hope Molecule
This reel that ended up changing my life was based on research from the University of Basel, popularized by Stanford’s Kelly McGonigal. They discovered a new protein released into the bloodstream during skeletal muscle contraction, called Myokines. Since their discovery, they have been labeled the “hope molecule”, as they are able to cross the blood-brain barrier and impact mood, acting as an anti-depressant, lowering anxiety, and improving ability to learn.[1]
A Molecular Cascade
Myokines are a part of a broader umbrella phenomenon called “muscle-brain cross-talk” that describes the molecular cascade of neurotransmitters released by the contraction of muscles. Dopamine, noradrenaline, and serotonin, all of which are crucial to mood regulation and motivation. Endorphins and oxytocin, which act as powerful bonding chemicals, making you feel more connected to those around you. All of which not only reduce negative emotion but amplify wellbeing.
Prevention or Cure?
These wide-ranging effects have usually been framed as preventative: good for avoiding of mental illness, but not powerful enough to use as a curative treatment. However, a recent large-scale meta-analysis of studies investigating the effect of exercise interventions on depressed patients gives a very different view.[2]
Largest Meta-Analysis to Date
Combining the results of 41 studies, and nearly 2300 participants, Heissel et al.’s 2023 analysis was the largest synthesis study to date, and the results are astounding. Moderate exercise interventions are shown to cause a significant reduction in depressive symptoms across the 2300 patients (SMD = 0.775, p<.001) which puts it on par with traditional psychotherapy (0.75), and far greater than anti-depressants (0.42). Medication tends to require more trial and error to get right, while exercise seems much more predictable. These numbers suggest exercise is at the very least comparable in effect as more traditional treatments.
Hyper-effective for light symptoms
Exercise worked especially well for those with lighter symptoms. The effect on those merely showing depressive symptoms was high (0.951, p<.001), and 1.7x higher than those fully diagnosed with Major Depressive Disorder (0.567, p=.003). This is the exact opposite pattern to anti-depressants, which tend to be much more effective in severe cases, leaving a treatment gap for mild cases.
Solution for Light-Case Overload?
Interestingly, this effect was even further amplified in cases where the individual was already on a waitlist for psychological care, (1.315, p<.001). This suggests it could be an especially effective intervention for those with less severe symptoms in the run-up to treatment. A possible solution for the saturation issue currently plaguing psychological treatment, where waitlists are filled with a high number of lighter symptom cases, leaving inadequate care for severe cases.
Better Together
The analysis helps us paint a detailed picture of what effective interventions could look like. Factors that were significant were group training over individual exercise (0.646 vs. 0.330), aerobic over resistance exercise (0.891 vs 0.508), and supervision over no supervision (0.769 vs. 0.119). Age did not have a significant effect on results. This gives one possible picture of what effective interventions could look like: supervised group sessions that focus on aerobic training, for individuals with less severe symptoms, open to all age groups.
Policy Blunder
While these findings received some publicity, and made their way into policy in the UK, the resulting policy grossly misinterpreted the findings. The policy created in response allowed psychiatric doctors to prescribe ‘going for a walk’, or ‘going outside’. At best this is a severe watering down, and at worst a gross misunderstanding of the research findings.
The Missed Dose-Effect
The study clearly shows a very strong dose-effect for exercise, with light exercise having much less effect (0.293, p=.383) on symptom reduction than moderate exercise (0.775, p<.001). A light walk is far less likely to have an impact than moderate exercise, and falls far below traditional methods.
Policy has missed the target by interpreting the study as “any exercise is good for wellbeing” (which is of course true) but ignore the data shows that moderate exercise is far better for reducing symptoms. Moderate and intense exercise are the only interventions that are on par with traditional methods, and therefore “should be offered as an evidence-based treatment.”
Obvious but Neglected
This might seem common sense, but a majority of the public does not put it into action. According to the WHO, only 19% of the world's adolescents meet their daily recommended physical activity needs. [3]In the UK's adult population, it's 40%. Even in the Netherlands, which ranked first in Ipsos’ 2021 report on most active nations, this figure is just 47%. [4] All the while, both the UK and NL are witnessing an ever-growing demand on mental healthcare, and public health systems failing to keep up [5]
I think accepting moderate exercise interventions as valid psychological treatment, increasing their availability, and funding research awareness around them would lead to a low-cost, scaleable, and effective way to reduce the current demand for mild symptom cases.
Conclusion:
Given these findings, moderate exercise should be considered not just preventative, but an evidence-based treatment for depression. With effects on-par or greater than the main treatments at the moment, it is currently a neglected yet effective solution to an urgent problem.
I talk from personal experience when I say, it has the potential to be not only prevent, but cure. To quote Nita Sweeney's autobiography title: "Depression hates a moving target."
Schnyder S, Handschin C. Skeletal muscle as an endocrine organ: PGC-1α, myokines and exercise. Bone. 2015 Nov;80:115-125. doi: 10.1016/j.bone.2015.02.008. PMID: 26453501; PMCID: PMC4657151.
Heissel A, Heinen D, Brokmeier LL, et al. Exercise as medicine for depressive symptoms? A systematic review and meta-analysis with meta-regression. British Journal of Sports Medicine 2023;57:1049-1057.
World Health Organization: WHO. (n.d.). Physical activity. https://www.who.int/news-room/fact-sheets/detail/physical-activity
Ipsos Global Advisor. (2021, August). Global Views On Exercise and Team Sports. https://www.ipsos.com/sites/default/files/ct/news/documents/2021-08/Global%20views%20on%20exercise_v6__1.pdf
Clews, G. (2022, November 24). ‘Startling’ increase in mental health service demand. Nursing Times. https://www.nursingtimes.net/news/mental-health/startling-increase-in-mental-health-service-demand-24-11-2022/
Cover Photo by Kalen Emsley on Unsplash
Nice post, and I like the short snappy sections for quick reading - thanks!
My main reflection is whether this is actually a neglected? Exercise is a huge industry, and I feel the psychological benefits as well as the physical are quite often utilised in marketing and advertising (though I may be biased given I go to the gym quite regularly). Perhaps the specific link to depression is leveraged less, but I feel its there by proxy in a lot of cases.
I guess a fairer question would be: what would need to exist, that doesn't currently, for this to be assessed as not a neglected issue?
Great point! And really appreciate the feedback on the sections - first post so good to know it works!
I totally agree. It’s somewhat of a dichotomy to me too… This massive presence of fitness as industry, and its relative absence when talking about psychological intervention.
Not Explicit Enough. The ‘Neglectedness’ comes for me by the connection not being made explicit enough — or, it’s made explicit by corporate fitness side, but not the therapeutic side. And so it is only administered through market forces, not medical forces. This quite fundamental and medically impactful activity has been left to companies to fulfil. Which also means the infrastructure only exists where it’s profitable to build it.
Institutional Distance. I guess we’ve seen a privatization of exercise. And the body of research that will prove its effects in the treatment field is only gaining traction now. It doesn’t have the robust, well-researched, institutionalised presence that other embodied treatments like mindfulness have gained.
Refined Interventions. Research would refine the interventions through medical-grade testing, something that corporate gyms approximate through popularity I guess. And it would make them available Where the patients are, and where it’s most needed. This is crucial, since I know for me the biggest barrier is always convenience.
Attitude Change. I think we also need to drive a wider change of attitude around exercise. Most of the public narrative around fitness has for decades been so focused on body-image, burning calories, or performance, the denial of pain and emotion, even self-punishment. These narratives can actively exclude those who struggle with any of these aspects. But luckily there are other ways of framing, which as you mentioned are now starting to show up in marketing - longevity benefits, ‘fitness a as feeling’, community etc. Great to see!
Bit long response but loved your question! Hadn’t actually considered this privatisation issue before. Guess state-sponsored exercise has a bit dark connotation - prisons, regimes... or just those lousy playpark gyms. Would be curious what your take is!