Question: what episode of criminal minds do they find out about reid's drug addiction?
Answer: Drug Addiction In (Season 2, Episode 15) "Revelations", Tobias Hankel (James Van Der Beek), a psychotic serial killer kidnaps Reid, drugging and torturing him over the course of two days before he is rescued. Reid is so traumatized that he develops an addiction to the narcotic painkiller Dilaudid.