Preliminary studies have shown chronic lung disease in some marijuana users. There are more known cancer-causing agents in marijuana smoke than in cigarette smoke. In fact, because marijuana smokers try to hold the smoke in their lungs as long as possible, one marijuana cigarette can be as damaging to the lungs as four tobacco cigarettes.

Even small doses of marijuana can impair memory function, distort perceptions, hamper judgment, and diminish motor skills. Health effects also include accelerated heartbeart and, in some persons, increased blood pressure. These changes pose health risks for anyone, but particularly for people with abnormal heart and circulatory conditions, such as high blood pressure and hardening of the arteries.

More importantly, there is increasing concern about how marijuana use by children and adolescents may affect both their short-and long-term development. Mood changes occur with the first use. Observers in clinical settings have noted increased apathy, loss of ambition, loss of effectiveness, diminished ability to carry out long-term plans, difficulty in concentrating, and a decline in school or work performance. Many teenagers who end up in drug treatment programs started using marijuana at early age.

Driving under the influence of marijuana is especially dangerous. Marijuana impairs driving skills for at least 4 to 6 hours after smoking a single cigarette. When marijuana is used in combination with alcohol, driving skills become even more impaired.