What is, overall, safer for your body: alcohol or marijuana?

Does acid (LSD) have a detrimental affect on women who use the birth control pill? Is it possible for a woman to be impregnated by pre-ejaculatory fluids four days after the menstrual cycle after unprotected sex?

My girlfriend tells me she uses marijuana to calm herself if she is having a stressful day. She has been doing this for many years. She says smoking pot is like self-medicating — it is better than using anti-depressants. She also claims smoking pot helps with depression because of how it helps produce serotonin in the body. What is serotonin and how does it help depression? Does smoking pot really help with managing your anxiety, depression, etc.?

I want to know what it is when you spontaneously trip without dropping tabs or anything. I've never had any drugs except marijuana. It is weird. I know that tripping is an induced psychosis, so am I psychotic or what? I was seeing a shrink and will be going back into treatment next semester. I think substance use is boring and a complete copout on life. I've made a lot of discoveries without needing to trip. Why does this happen? Tell me what you know.

I have a history of "experimentation" (infrequent or occasional use of ecstasy, 'shrooms, and other drugs — mostly prescription pills). I am completely sober now, but am worried about long-term damage to my brain. I used drugs infrequently (no more than three to five times for each substance), but drank regularly. How worried should I be? Is there anything I can do to combat long-term effects?

Recently, I have heard about a new hallucinogen available called salvia dinorium. Some of my friends have tried it and they tell me it is an incredible experience and that when you hallucinate, you have the perception of being brought back in time. Before I even think about trying this, however, I would like to have a more precise idea of what the effects are and what the possible risks of taking salvia are.