Does exercise actually help depression?

These trials compared exercise with medication in people starting treatment. None of them tested stopping medication and replacing it with exercise. Antidepressants should never be stopped or reduced without the prescriber who started them — discontinuation has its own risks, and doing it alone is how people get hurt.

The SMILE studies (Blumenthal et al.) — not to be confused with the SMILES diet trial covered on the Food & Mood page, a completely different study by a different team.

• 1999 (Archives of Internal Medicine): older adults with major depression; aerobic exercise, sertraline, or both; 16 weeks; comparable outcomes across all three arms.
• SMILE-II, 2007 (Psychosomatic Medicine): 202 adults randomized to supervised group exercise, home-based exercise, sertraline (50–200 mg), or placebo pill, 16 weeks. Exercise and sertraline produced comparable improvement, both greater than placebo.
• Babyak et al. (2000), 10-month follow-up: the exercise group showed lower relapse than the medication group.

Well-supported. These were specific samples — largely middle-aged and older adults with major depression, not a general claim covering everyone on medication.

Noetel et al., BMJ 2024;384:e075847 — a network meta-analysis of 218 studies, 495 arms, 14,170 participants. Compared with active controls:

Effects were proportional to prescribed intensity. Strength training and yoga had the best adherence.

What the numbers mean, plainly: Hedges' g is an effect size — roughly, how big the improvement was compared with people who didn't do that activity. As a rough guide, 0.2 is a small effect, 0.5 is moderate, 0.8 is large. Every modality in the table lands in the small-to-moderate range, and the "95% credible interval" is the range the true effect probably falls in — none of these intervals cross zero, meaning the improvement itself is real, even though the exact size is uncertain.

The caveat, in the same breath, not buried: only one of the 218 studies met Cochrane's criteria for low risk of bias, and the review's own confidence grading was low for walking/jogging and very low for everything else. Nobody can be blinded to whether they're exercising, so expectancy effects are unresolved by design — the authors say this themselves.

The honest answer is less exciting than the internet's. The review above already ranks the major modalities, and high-intensity interval training did not emerge as a separate winner — the headline is that differences between modalities are smaller than the gap between doing something and doing nothing.

Effects scaled with prescribed intensity, but strength training and yoga had the best adherence. Those two findings pull against each other, and naming the tension is the useful part: the hardest session you'll quit loses to the moderate one you'll repeat.

Resistance training and anxiety have their own meta-analytic support (Gordon et al., 2017) Well-supported — worth naming on its own, since resistance training is under-represented in mental-health advice compared to cardio.

Interval training is efficient for cardiorespiratory fitness, but for depression specifically it hasn't outperformed steadier work, and it has the worst adherence profile in most trials. The steadier option here is easy aerobic effort you can hold a conversation through.

The practical close: the answer is the one you'll do twice next week. See the habit tracker for building that repeatably.

Harvey et al. (2018), the HUNT cohort — modest regular activity was associated with lower incidence of later depression. Promising (a cohort study, not a randomized trial, so it can't establish direction on its own).

Single bouts of exercise show acute mood and anxiety benefits in the shorter-term literature, alongside the resistance-training finding above. See Stress and Anxiety for the fuller pictures those pages build.

Different question, different evidence — this is about longevity and physical outcomes, not mood, kept to one section on purpose.

• Cardiorespiratory fitness and all-cause mortality (Mandsager et al., JAMA Network Open, 2018).
• Resistance training and mortality (Momma et al., BJSM, 2022).
• Grip strength as a mortality correlate — an association, not a lever; squeezing harder isn't an intervention.
• Exercise and hippocampal volume or executive function in older adults. Promising — early effect sizes have shrunk under replication.

The takeaway: across several large studies, people who are fitter or stay active tend to live longer and keep sharper thinking as they age. None of this proves exercise causes longevity on its own — fitter people may simply be healthier to begin with — but it's a consistent, independent reason to move, separate from anything about mood.

Not a training programme. The honest finding is that effects scale with intensity and that adherence beats intensity — the walk you'll repeat outperforms the session you'll abandon. Build it with the habit tracker, one small repeatable step rather than an ambitious plan.