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Letter From the Director

Image of a marijuana plantWhat is Marijuana? Marijuana— also called weed, herb, pot, grass, bud, ganja, Mary Jane, and a vast number of other slang terms— is a greenish-gray mixture of the dried, shredded leaves and flowers of Cannabis sativa— the hemp plant.

Changes in marijuana policies across states legalizing marijuana for medical and/or recreational use suggest that marijuana is gaining greater acceptance in our society. Thus, it is particularly important for people to understand what is known about both the adverse health effects and the potential therapeutic benefits linked to marijuana.

Because marijuana impairs short-term memory and judgment and distorts perception, it can impair performance in school or at work and make it dangerous to drive an automobile. It also affects brain systems that are still maturing through young adulthood, so regular use by teens may have a negative and long-lasting effect on their cognitive development, putting them at a competitive disadvantage and possibly interfering with their well-being in other ways. Also, contrary to popular belief, marijuana can be addictive, and its use during adolescence may make other forms of drug abuse or addiction more likely.

Whether smoking or otherwise consuming marijuana has therapeutic benefits that outweigh its health risks is still an open question that science has not resolved. Although many states now permit dispensing marijuana for medicinal purposes and there is mounting anecdotal evidence for the efficacy of marijuana-derived compounds, there are currently no FDA-approved indications for “medical marijuana.” However, safe medicines based on cannabinoid chemicals derived from the marijuana plant have been available for decades and more are being developed.

This Research Report is intended as a useful summary of what the most up-to-date science has to say about marijuana and its effects on those who use it — both young and old.

Nora D. Volkow, M.D.
National Institute on Drug Abuse

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This page was last updated April 2015

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