Question: what episode of criminal minds does reid go to rehab?
Answer: In (Season 2, Episode 15) "Revelations", Tobias Hankel (James Van Der Beek), a serial killer with dissociative identity disorder, 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.