People put it in rolling papers to make marijuana cigarettes, smoke it in bongs or pipes, or mix it in baked goods or tea and eat or drink it. The cannabis plant also yields hashish, a stronger form of marijuana, and hash oil, the strongest form that has very high levels of THC, the psychoactive ingredient in cannabis.
Marijuana contains several psychoactive chemicals that act on the brain.
While scientists do not know all of the drug's effects, several studies have established that marijuana interferes with memory and learning. These deficits persisted up to 24 hours after users stopped feeling high. Marijuana also impairs judgment and reaction time. Road tests for marijuana intoxication are not routinely done, but a special study in Memphis, Tennessee, showed that one-third of drivers stopped for reckless driving were high on marijuana. Daily use of from 1 to 3 marijuana cigarettes appears to produce the same lung damage and cancer risk as smoking 5 times as many cigarettes.