The most prominent researcher in LSD therapy was Stan Grof. Look up his books - they are the definitive material for psychiatric work using psychedelics. There are experiences in the books that will blow your mind. I believe he was head of the psychiatry department at Johns Hopkins, before this research was shut down.

However, it is interesting that he now appears to be a proponent of meditation and other methods, as far as I know. He teaches an interesting technique called holotropic breathing which aims to replicate the benefits without the risk.

I think a prominent meditation teacher summed it up best when he said that psychedelics can lead to a powerful opening, but they are not a path.