My son is 13 and has ocd.would giving him the supplement"seratonin" from a gnc store help him?

Maybe, but...: Maybe, but that is not the best option. It is impossible to know the dosing and purity of those compounds. He should see a doctor for a prescription, and will probably need counseling. Good luck.

UnknowN: Possible but would depend what is in it and if the products are good.

Mental Health: Please. Be cautious. A thirteen year old's brain is still developing. I would not advise any product unless specifically recommended by the physician managing and monitoring your son's care.