I have a bad back, its like the muscles are overstrained and it gets knotted sometimes. I constantly twist and turn or push and whatnot to crack my back and when I smoke it gets a bit more tense. I don't know if it has to do with stress, but most people report that marijuana helps there pain, in my case it seems to worsen it. I get tired when I smoke as well. I may just need to get myself in shape, but this is what I feel.
Aside from that, it's something that passes the time, and also makes me forget about most problems and relax.
If anyone else experiences symptoms like my own, with the back pain and such, please post.