Ritalin is very popular for ADD/ADHD
. Celexa is an SSRI which is used for depression and can also be used to treat OCD.
Once again, I am no doctor, but I would recommend getting a second opinion, maybe more thorough. How many times did your son see the psychiatrist? If he made all those diagnosis on a single visit, I would a little hesitant. I have learned to always question doctors until you find one you are comfortable with and trust.