The immediate effects of taking marijuana include rapid heart beat, disorientation, lack of physical coordination, often followed by depression or sleepiness. Some users suffer panic attacks or anxiety. But the problem does not end there. According to scientific studies, the active ingredient in cannabis, THC, remains in the body for weeks or even months. Marijuana smoke contains 50% to 70% more cancer-causing substances than tobacco smoke.24 One major research study reported that a single cannabis joint could cause as much damage to the lungs as up to five regular cigarettes smoked one after another.