Im sure your lungs will thank you later.
Smoking anything, of course, is detrimental
to your
lungs. Second, Marijuana abuse alone does NOT cause any physical abnomalities to your brain, so the answer to question number two is "no scan". Marijauna/THC acts as a Serotonin reuptake inhibitor, allowing you to have higher serotonin levels. Serotonin is a feel good chemical. Antidepressants that fall into the SSR catagory do the same thing.