Smoking before your body and brain are done developing might not be a great idea either, even if you don't have a family history of mental illness. But again, there has been very little research done in this area. That's a problem with the laws: because it's a Schedule I drug, it's difficult to do good research, so we're all left stumbling in the dark wondering about stuff that we could figure out if only the laws would allow the research.

I doubt it's completely harmless, but few things are completely harmless if you do them too much. On the other hand, taken in moderation, if you're past puberty and have no history or predisposition toward mental illness, I doubt it does much harm. I've smoked on and off for 27 years now, and other than temporarily degrading my vocabulary, I've noticed no bad effects myself -- but I smoke in moderation now, and haven't smoked what I would call heavily for quite some time.

If you're smoking to enhance your life, that's fine. If you're smoking to escape reality, that's when there's a problem. The problem isn't the pot, it's the attempt to escape reality. That always comes back to bite you in the ass.