Individuals with genetic variants that increase the likelihood of being physically active are protected from depression.

“Moreover these findings have a stronger case for causality thanks to a technique called Mendelian randomization Mendelian randomization treats natural genetic variation like a randomized experiment it is science individuals to higher or lower mean levels of an environmental exposure which in this case is physical activity this type of genetic study is able to establish causality in a way that observational studies cannot but only to the extent that these genetic variants influence depression directly through physical activity and not some other unknown mechanism”