3) 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.
4) If it doesn't kill brain cells, how does it get you `high'?
Killing brain cells is not a pre-requisite for getting `high.' Marijuana contains a chemical which substitutes for a natural brain chemical, with a few differences. This chemical touches special `buttons' on brain cells called `receptors.' Essentially, marijuana `tickles' brain cells. The legal drug alcohol also tickles brain cells, but it will damage and kill them by producing toxins (poisons) and sometimes mini-seizures. Also, some drugs will wear out the buttons which they push, but marijuana does not.
5) Don't people die from smoking pot?
Nobody has ever overdosed. For any given substance, there are bound to be some people who have allergic reactions. With marijuana this is extremely rare, but it could happen with anything from apples to pop-tarts. Not one death has ever been directly linked to marijuana itself. In contrast, many legal drugs cause hundreds to hundreds of thousands of deaths per year, foremost among them are alcohol, nicotine, valium, aspirin, and caffiene. The biggest danger with marijuana is that it is illegal, and someone may mix it with another drug like PCP.
Marijuana is so safe that it would be almost impossible to overdose on it. Doctors determine how safe a drug is by measuring how much it takes to kill a person (they call this the LD50) and comparing it to the amount of the drug which is usually taken (ED50). This makes marijuana hundreds of times safer than alcohol, tobacco, or caffiene. According to a DEA Judge "marijuana is the safest therapeutically active substance known to mankind.''
6) I forgot, does marijuana cause short-term memory impairment?
The effect of marijuana on memory is its most dramatic and the easiest to notice. Many inexperienced marijuana users find that they have very strange, sudden and unexpected memory lapses. These usually take the form of completely forgetting what you were talking about when you were right in the middle of saying something important. However, these symptoms only occur while a person is `high'. They do not carry over or become permanent, and examinations of extremely heavy users has not shown any memory or thinking problems. More experienced marijuana users seem to be able to remember about as well as they do when they are not `high.'
Studies which have claimed to show short-term memory impairment have not stood up to scrutiny and have not been duplicated. Newer studies show that marijuana does not impair simple, real-world memory processes. Marijuana does slow reaction time slightly, and this effect has sometimes been misconstrued as a memory problem. To put things in perspective, one group of researchers made a control group hold their breath, like marijuana smokers do. Marijuana itself only produced about twice as many effects on test scores as breath holding. Many people use marijuana to study. Other people cannot, for some reason, use marijuana and do anything that involves deep thought. Nobody knows what makes the difference.
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. If marijuana use were truly a causative factor for schizophrenia, the United States likely would have seen a large increase in cases of schizophrenia in the last 30 years as a result of increased use in the 1960s and 1970s. However, a review of epidemiological evidence up to 1990 failed to show these results, suggesting the relationship between marijuana use and psychiatric illness is not completely direct (Thornicroft 1990).
I can go on forever showing studies that disprove this myth.