Marijuana can cause panic attacks in some people. Mainly in people who have been smoking for a long time, however, I suffered panic attacks after only 4 months of smoking. Marijuana stimulates the pleasure cells in your brain. If you wan't a scientific answer do a web search. Personally, marijuana affects on me were : increased taste, increased hunger, increased sense of hearing, increased sexual pleasure, increased interest in simple or mundane activities, increased paranoia, and sedation.