Evidence suggests that marijuana use during pregnancy may be sufficient to produce permanent fetal abnormalities, and if combined with other drug use, inadequate prenatal care or malnourishment, harm to the fetus may increase greatly. Marijuana also produces inability to complete psychomotor tasks. Driving performance is impaired, due to altered perception of space and time, and reduced ability to make quick decisions. Marijuana intoxication interferes with other skills such as communicating, or recalling verbal or graphic material from short-term memory. The degree of impairment depends on the dose and potency of the drug, the individual's tolerance, and the complexity of the task.
Many feelings experienced by marijuana users are subjective in nature.
Feelings may include euphoria, relaxation and hilarity, and negative psychological reactions include panic attacks, anxiety and hallucinations. Although it is difficult to measure objectively, researchers have expressed concern over marijuana's effects on motivation. A picture has emerged of amotivational syndrome , which can be described as a massive and persistent loss of ambition that is replaced by chronic apathy and passivity toward goals and the future. Amotivational syndrome is seen most frequently in heavy marijuana users. Tolerance to a drug develops when increasing doses of a drug are required to produce the same effect.