This just an observation without any study backing it. But people who do more physical labour as opposed to sitting at the couch really do have less rates of OCD. Why this association of physical work with OCD's?
By OCD, I mean Obsessive Compulsive Disorder.
Here's a study backing up the exercise and its positive effects on reduction of OCD, https://www.ncbi.nlm.nih.gov/m/pubmed/17568300/