If a little bit of something is good, then a lot of it must be great, right? When it comes to exercise — as with drugs, food, video games, porn, and all manner of other things that make us feel good — it turns out this is probably not true.
In a paper published Wednesday in The Lancet Psychiatry, a team of psychiatry, data, and health researchers examined data from 1.2 million people over a 4-year period and found that people who exercise regularly had about 1.5 fewer days of poor mental health a month than their non-exercising peers who were otherwise similar to them in terms of economic, demographic, and mental health factors. They found that the association between exercise and better mental health was the strongest for people who exercised 60 to 90 minutes three to five times a week, but even people who engaged in mild exercise like walking for 45 minutes three times a week saw benefits.
Surprisingly, they also found that more exercise isn’t necessarily better. People who exercised more than 23 times a month or longer than 90 minutes at a time reported worse mental health outcomes.
“People who walked three times a week seemed to have better mental health than people who did nothing,” Adam Chekroud, Ph.D., an assistant professor of psychiatry at Yale University and one of the authors on the new study, told Inverse. “So really it’s not a case where you need to go out and do crazy resistance training or body sculpting or intense workouts. It seems like these benefits were happening just from relatively low amounts of regular exercise.”
He also points out, though, that since this is just a cross-sectional study, it doesn’t necessarily indicate whether exercise improves mental health or whether better mental health motivates people to exercise more.
“There’s a clear association, we just maybe don’t know which way it goes,” said Chekroud. “In fact there’s actually evidence suggesting that it goes both ways: People who exercise do seem to have better mental health, but people who have worse mental health are also less likely to exercise, so there’s definitely a two-way relationship.”
Of course, when it comes to people for whom excessive exercise is associated with poorer mental health, this two-way relationship could also be at play. In addition to the stereotype of someone whose obsession with fitness leads them to exercise excessively, Chekroud points out that high levels of exercise itself could contribute to worse mental health.
“If you do a high volume of exercise, you are stressing your body out, and maybe that’s leading to things like inflammation, which is already associated with things like depression as well,” he said. That being said, the new study doesn’t really dig into these answers, so currently, all we can do is speculate based on what we already know about fitness and mental health. But Chekroud, who recently co-founded a mental health startup called Spring Health, hopes that these data will provide a foundation for personalized exercise programs to optimize depression treatment.
“The goal will be to use large datasets and all this information that we have and mine that to come up with personalized plans so that you could just do a quick assessment and then it will recommend for you personally what kind of exercise is best for your mental health,” he said.
For now, just know that some exercise is better than no exercise.