It has been shown that marijuana users are six times more likely to develop schizophrenia than are non-users. Marijuana use is associated with the development of Amotivational Syndrome. Often the relationship of impairments and symptoms to marijuana use becomes evident only when the user is persuaded to stop, shows clear-cut improvement in mood and behavior, and describes a feeling of coming out of a fog. Memory defects may persist six weeks after last use. Marijuana causes both dependence and addiction.
Addictive use is defined by compulsive, repeated use in spite of adverse consequences.
Marijuanas effects include tolerance, leading to dependence, and then inability to cease use. In many parts of the country, there are more people admitted to drug treatment centers because of marijuana addiction than heroin addiction. The effects of marijuana, which is fat-soluble, persist much longer than the effects of alcohol, which is water soluble. An experiment on pilots, using a computerized flight simulator, showed that their ability to land a plane was still impaired 24 hours after smoking a single marijuana cigarette. The use of marijuana during pregnancy is associated with babies of low birth weight.