My friend is suffering from stage 2 schizophrenia.his doctor stated, its because of weed he use to smoke daily since a year. is weed that harmfull?

Unlikely: To my knowledge, there is no definitive research that supports this conclusion. More likely is that genetics influenced the development of schizophrenia. It's possible that heavy marijuana use sped up the process. Also likely he was in the prodromal stage of schizophrenia and was using marijuana to mask the symptoms he was having. Your friend will need your support. Good luck to you both.