OCD is an evolutionary adaptation, but it's not what evolutionary psychologists think. While it's true that obsessions have evolutionary underpinning, it's not true that they cause the OCD. Those obsessions, even though central to OCD, are completely irrelevant to its cause. Well, what I am talking here?

OCD is caused by a gene-environmental mismatch in one or more areas that forbid the expression of natural drive. For example, wild lions who hunt for all their lives. One day, you put them in cages with no social contact. Soon, they'll start obsessively licking themselves. While you can argue that licking (grooming) has evolutionary roots, you CAN'T say that it causes OCD!

Personally, my OCD is always triggered when I am in an environment where I can't compete. I'm fiercely competitive. So, if you put me in a typical American classroom where professors' pets get the best grades, not those who know most, then I begin to worry whether I have HIV, whether my hands are clean enough, whether I shower enough and stuff like that. Once I shifted to online coding competitions to satisfy my competitive drive, I no longer have OCD. No SSRIs. No Exposure and Response Prevention Therapy required.