The study showed that exercise caused lower depression risk, but depression was not linked to less exercise.
Just 15 minutes of running per day is enough to significantly reduce depression risk, a genetic analysis concludes.
Alternatively, around one hour of moderate activity will do the same job.
However, any activity at all — including housework and gardening — is better than none for reducing depression risk.
The conclusions come from a genetic analysis of almost half a million people.
Dr Karmel Choi, the study’s first author, explained the key result:
“On average, doing more physical activity appears to protect against developing depression.
Any activity appears to be better than none; our rough calculations suggest that replacing sitting with 15 minutes of a heart-pumping activity like running, or with an hour of moderately vigorous activity, is enough to produce the average increase in accelerometer data that was linked to a lower depression risk.”
While more exercise has frequently been linked to lower depression risk, it is hard to determine cause and effect.
The difficulty is that people who are depressed may move around less.
So, does depression cause less exercise or is more exercise the cause of less depression?
To resolve this problem, the new study used a different method based on genetics.
Dr Karmel Choi, the study’s first author, said:
“Using genetic data, we found evidence that higher levels of physical activity may causally reduce risk for depression.
Knowing whether an associated factor actually causes an outcome is important, because we want to invest in preventive strategies that really work.”
The new conclusions are based on data from almost half-a-million people, 91,000 of whom wore wrist bands that measured their physical activity.
The study showed that exercise caused lower depression risk, but depression was not linked to less exercise.
Dr Choi and colleagues will now go on to look at who might benefit from exercise the most:
“We currently are looking at whether and how much physical activity can benefit different at-risk groups, such as people who are genetically vulnerable to depression or those going through stressful situations and hope to develop a better understanding of physical activity to promote resilience to depression.”
The study was published in the journal JAMA Psychiatry (Choi et al., 2018).
