Induced Paranoia

What if there were a group of close knit friends. two of whom had mental illnesses, that were not yet diagnosed, the other was a completely healthy person. then over time, the third friend started going crazy, not because he was predisposed to mental illness, but constant exposure to his crazy friends triggered a chemical imbalance in his brain that rendered him completely insane? what if psychosis can be passed on through chemical functions in the brain to others? how do girls periods' all synchronize to be around the same time? with the scent. perhaps crazies have a scent that slowly degenerates the brain. 

maybe a short story will come of this!