- A large review found that people with better cardiorespiratory fitness were less likely to develop depression, dementia and psychotic disorders.
- Even small gains in fitness were linked to lower risk, suggesting the benefits are not limited to highly athletic people.
- The findings are promising, but they do not prove that improving fitness alone will prevent mental illness or dementia.
Researchers reviewed 27 prospective studies involving more than 4 million people.
All participants were free of mental or neurocognitive disorders at the start, then followed over time.
The question was simple.
Did fitter people go on to develop fewer mental health problems?
Overall, the answer appeared to be yes.
Higher cardiorespiratory fitness was linked to a 36% lower risk of depression, a 39% lower risk of dementia and a 29% lower risk of psychotic disorders.
There was also a possible link with lower anxiety risk, but that result was weaker and not statistically convincing.
One of the more useful findings was that the benefit did not seem to require dramatic changes.
A one-MET increase in fitness, which is a fairly modest improvement, was linked to a roughly 5% lower risk of depression and a 19% lower risk of dementia.
That matters because it suggests the potential gains are not just for runners or gym enthusiasts.
They may be relevant at population level.
This is also a stronger type of evidence than the usual cross-sectional study, because the researchers looked at prospective cohorts.
- Metformin may mimic some exercise-related metabolic effects in prostate cancer care
- Mid-life movement and sleep patterns may hint at lifespan
- Inactivity may drive up to 10% of major type 2 diabetes complications
Even so, it is still observational evidence.
That means it cannot prove that low fitness causes these conditions, or that raising fitness will definitely prevent them.
But the overall message is still important.
Cardiorespiratory fitness looks like a meaningful, measurable and modifiable marker that may have a role in mental health and brain health prevention.
