Does marijuana produce serotonin?

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.?


How many times a day do people typically get erections?

Should a normal man's penis become erect for a certain number of times throughout one day (without any external stimulus)? Or, do these erections occur only while a man is sleeping? I have been masturbating once every day or every other day, and I have noticed that I rarely get any of those spontaneous erections during the day at all. Plus, I have been waking up with no morning erection during the past week. Have I been masturbating too much?