rationalskepticism.org

Not as bad as some other habits, especially ones that change your mood. Inhaling smoke is bad no matter the source, and after being diagnosed with mild emphysema I read some papers and it sounds like smoking cigarettes and marijuana combined increases the risk of emphysema over just smoking cigarettes. I had quit cigarettes 5 years before being diagnosed with the emphysema, but could have had the emphysema for years without even knowing because I have asthma and the symptoms are identical. Asthma alone, or with cigarettes is also a risk factor for emphysema. It's not possible for me to tell whether it was the marijuana that caused it, but I quit smoking it the moment they told me about having emphysema. If I had a kid, I'd advise them to not smoke anything, ever. I haven't heard a bad word about taking it with food, and don't have any serious side effects, except for the munchies, which are a lot worse than with smoking. I've gained 30 pounds, which isn't good. But the marijuana isn't making me put food in my mouth, and I'm also on much stronger medication that causes weight gain, again muddying the water.
After quitting, I have never breathed better in my life than right now, and breathing tests give a lung age commensurate with my chronological age. So smoking it was still exacerbating my breathing symptoms even though I couldn't tell at the time.
That's all I can do, tell you about my experience. The act of getting high probably doesn't hurt much, but the smoking definitely hurts at least a little.