Long-term use causes the psychedelic part of THC effects to diminish over time. At some point, only a mild depressant effect remains - somewhat similar to chamomile. It does have some effect on intelligence and short-term memory, but if the alternative is to be too stressed to think at all, it might be better to just smoke.

Obviously, if possible, psychotherapy or a prescription from a psychiatrist (or better yet, a change of environment) would be better (in the latter case, it depends on the prescribed drug, of course), but THC is not that bad an alternative where it's legal.