I mean, they're all just different kinds of chemical imbalances in the brain, not something physical. Something firing when it shouldn't or not firing when it should. A good amount of people in my family have various mental disorders: bipolar, schizophrenia etc. I don't have those but I do have a mild-moderate stutter and other random ticks/obsessions (OCD things like counting, something needing to be even in number like I previously mentioned, etc). Makes me think they're all related in some general way. Like a family with 1st cousins, 2nd, 3rd etc. edit spelling