Doesn't Marijuana cause brain damage?

The short answer: No.

The long answer: The reason why you ask this is because you
probably heard or read somewhere that marijuana damages
brain cells, or makes you stupid. These claims are untrue.

The first one -- marijuana kills brain cells -- is based on
research done during the second Reefer Madness Movement. A
study attempted to show that marijuana smoking damaged brain
structures in monkeys. However, the study was poorly
performed and it was severely criticized by a medical review
board. Studies done afterwards failed to show any brain
damage, in fact a very recent study on Rhesus monkeys used
technology so sensitive that scientists could actually see
the effect of learning on brain cells, and it found no
damage.

But this was Reefer Madness II, and the prohibitionists were
looking around for anything they could find to keep the
marijuana legalization movement in check, so this study was
widely used in anti-marijuana propaganda. It was recanted
later.

(To this day, the radical anti-drug groups, like P.R.I.D.E.
and Dr. Gabriel Nahas, still use it -- In fact, America's
most popular drug education program, Drug Abuse Resistance
Education, claims that marijuana ``can impair memory
perception & judgement by destroying brain cells.'' When
police and teachers read this and believe it, our job gets
really tough, since it takes a long time to explain to
children how Ms. Jones and Officer Bob were wrong.)

The truth is, no study has ever demonstrated cellular
damage, stupidity, mental impairment, or insanity brought on
specifically by marijuana use -- even heavy marijuana use.
This is not to say that it cannot be abused, however.