РефератыИностранный языкMaMarijuana In Detail Essay Research Paper

Marijuana In Detail Essay Research Paper

Marijuana In Detail Essay, Research Paper


"Marijuana causes long-term changes in the brain similar to those seen with


other drugs of abuse . . ." Back in the 1970s, animal experiments led to


groundless fears that marijuana blew holes in brain tissue. The experiments


organisations like NIDA now fund are more sophisticated but the controversy


still rages. George Koob, an addiction researcher from The Scripps Research


Institute in La Jolla, California, claims the new message from the animals is


simple: "The more we discover about the neurobiology of addiction the more


common elements we’re seeing between THC (tetrahydrocannabinol, the main active


ingredient in cannabis) and other drugs of abuse." And for Koob, one of


these newly discovered "common elements" is marijauna’s ability to


trigger chemical changes in the brain that lead to strong withdrawal symptoms.


In humans, some researchers claim to see clear evidence of insomnia, anxiety and


even flu-like symptoms in heavy cannabis users who abstain. But if there’s a


consensus, it’s that symptoms are mild and variable. By contrast, Koob’s rats


are shivering wrecks. Does this mean marijuana is more addictive than we think?


Not a bit of it, says Roger Pertwee, a university pharmacologist and president


of the Cannabinoid Research Society. That’s because those symptoms aren’t so


much observed as manufactured. The animals are injected with high doses of THC,


then injected with a second chemical to block cannabis receptors in the brain.


Without the block, the sharp withdrawal symptoms can’t be seen because cannabis


clears so slowly that even heavily doped rats are likely to experience a gentle


wind down. Another debate rages over animal studies into the short-term effects


of marijuana on brain chemistry. Heroin, cocaine, alcohol and nicotine all


trigger a surge in the chemical dopamine in a small midbrain structure called


the nucleus accumbens. Many researchers regard this as a hallmark of an


addictive substance. Last year, experiments showed that cannabis presses the


same dopamine button in rats, leading to claims that the drug must be more


addictive than previously thought. To critics, it is just another example of


those old exaggerated fears. What nobody tells you, says John Morgan, a


pharmacologist at City University of New York Medical School, is that rats don’t


like cannabis. It’s easy for them to get hooked on heroin or cocaine — but not


marijuana. Nor, Morgan claims, are researchers exactly open about awkward


observations, such as the fact that there are plenty of nonaddictive drugs that


stimulate dopamine in the brain. It’s easy to understand why biologists want to


find simple chemical traits that are shared by all addictive drugs.


Unfortunately, the differences are as important as the similarities when it


comes to weighing the relative risks and pleasures involved in taking drugs. And


subjectively at least, the intense rush of cocaine and orgasm-like high of


heroin have little in common with dope’s subtler effects. A compound related to


the active ingredient in marijuana may be accumulating in the spinal fluid of


people with schizophrenia. This might explain why many sufferers smoke pot. Many


researchers blame schizophrenia on an overactive dopamine system in the brain.


Daniele Piomelli and colleagues at the University of California at Irvine


already knew that making rats? dopamine receptors hyperactive caused a surge in


anandamide, a lipid that binds to the same receptors in the brain as marijuana.


Now Piomelli?s group has examined cerebrospinal fluid from 10 schizophrenic


patients, taken for diagnostic purposes at the Medical College of Hannover in


Germany. They found that fluid from schizophrenic patients had on average twice


as much anandamide as fluid from people who didn?t have schizophrenia (NeuroReport,


vol 10, p 1665). One explanation for the higher levels in schizophrenics is that


the brain is attempting to compensate for a hyperactive dopamine system. ?It?s


the brain?s response to bring this dopamine activity down,? says Piomelli. But


the brain cannot keep the amount of anandamide high enough to lower dopamine


levels, he says. This might also explain why schizophrenics often smoke


marijuana. The drug?s active agent, THC, and anandamide both bind to the same


receptor, so patients might be treating themselves, he says. But because pot


does not act selectively in the brain, Piomelli does not consider it a useful


treatment for schizophrenia. ?I don?t think the patient wants to be high,? he


says. ?I think the patient wants to feel better.? One weakness in the data so


far is that five of the patients were taking medication for their symptoms and


three others were using marijuana daily. The effects of these drugs on


endogenous cannabinoid levels is not known. ?It is imperative to continue with


a larger sample,? says Piomelli. The researchers are now testing fluid from


more patients to see if the correlation still holds true. Health officials in


Geneva have suppressed the publication of a politically sensitive analysis that


confirms what ageing hippies have known for decades: cannabis is safer than


alcohol or tobacco. According to a document leaked to New Scientist, the


analysis concludes not only that the amount of dope smoked worldwide does less


harm to public health than drink and cigarettes, but that the same is likely to


hold true even if people consumed dope on the same scale as these legal


substances. The comparison was due to appear in a report on the harmful effects


of cannabis published last

December by the WHO. But it was ditched at the last


minute following a long and intense dispute between WHO officials, the cannabis


experts who drafted the report and a group of external advisers. As the WHO’s


first report on cannabis for 15 years, the document had been eagerly awaited by


doctors and specialists in drug abuse. The official explanation for excluding


the comparison of dope with legal substances is that "the reliability and


public health significance of such comparisons are doubtful". However,


insiders say the comparison was scientifically sound and that the WHO caved in


to political pressure. It is understood that advisers from the US National


Institute on Drug Abuse and the UN International Drug Control Programme warned


the WHO that it would play into the hands of groups campaigning to legalise


marijuana. One member of the expert panel which drafted the report, says:


"In the eyes of some, any such comparison is tantamount to an argument for


marijuana legalisation." Another member, Billy Martin of the Medical


College of Virginia in Richmond, says that some WHO officials "went


nuts" when they saw the draft report. The leaked version of the excluded


section states that the reason for making the comparisons was "not to


promote one drug over another but rather to minimise the double standards that


have operated in appraising the health effects of cannabis". Nevertheless,


in most of the comparisons it makes between cannabis and alcohol, the illegal


drug comes out better–or at least on a par–with the legal one. The report


concludes, for example, that "in developed societies cannabis appears to


play little role in injuries caused by violence, as does alcohol". It also


says that while the evidence for fetal alcohol syndrome is "good", the


evidence that cannabis can harm fetal development is "far from


conclusive". Cannabis also fared better in five out of seven comparisons of


long-term damage to health. For example, the report says that while heavy


consumption of either drug can lead to dependence, only alcohol produces a


"well defined withdrawal syndrome". And while heavy drinking leads to


cirrhosis, severe brain injury and a much increased risk of accidents and


suicide, the report concludes that there is only "suggestive evidence that


chronic cannabis use may produce subtle defects in cognitive functioning".


Two comparisons were more equivocal. The report says that both heavy drinking


and marijuana smoking can produce symptoms of psychosis in susceptible people.


And, it says, there is evidence that chronic cannabis smoking "may be a


contributory cause of cancers of the aerodigestive tract". HEAVYusers of


marijuana who suddenly go cold turkey have aggressive impulses as powerful as


those felt by Frank Spooner The reaction is far less intense than the withdrawal


symptoms of alcoholics or people addicted to cocaine or heroin, and may reflect


a psychological dependence on the drug, rather than a genuine physiological


addiction. But it still might be enough to keep some marijuana users from


kicking their habit, says Elena Kouri, a psychologist at Harvard Medical School


in Boston. Kouri and her colleagues recruited 17 volunteers who had smoked


marijuana on at least 5000 occasions, and who continued to be heavy users of the


drug. They also studied 20 people who either took marijuana occasionally, or who


had already given it up. None of the volunteers had a history of violence or any


other psychiatric disturbance. The researchers used a computer game to measure


the volunteers’ aggressive behaviour during a 28-day period of abstinence from


marijuana, which was monitored by daily, supervised urine tests. The volunteers


sat alone at a computer screen with two buttons. The first added money to an


account in their name, but they were told that a second would subtract money


from the account of their opponent, sitting at a similar screen in the next


room. On the day they gave up marijuana, and one, three, seven and 28 days


later, the two players were given 20 minutes to take it in turns to push one or


other button, after which they could keep the money left in their account. In


reality, there was no opponent. The researchers had instead arranged for the


computer to provoke the volunteers by frequently subtracting money from their


account. When tested on the third and seventh days of abstinence, this ersatz


"nasty opponent" managed to get the heavy users noticeably hot under


the collar. Says Kouri: "Subjects that on day zero hadn’t cared at all that


they were losing points started swearing and punching the keyboard, yelling ‘I’m


going to get you back!’" The heavy users hit the "punishment


button" more than twice as often as the control group on days three and


seven– an increase in aggression that compares roughly with that produced by a


three-week course of testosterone supplements in another study by Kouri. The


increased aggression had subsided completely by the time the volunteers were


tested again at the end of the abstinence period, however (Psychopharmacology,


vol 143, p 302). The study is the first to measure aggression during withdrawal


from a long period of heavy marijuana use. But Margaret Haney, a psychologist at


Columbia University in New York, says that people who show aggressive tendencies


in the laboratory do not necessarily become violent in the real world. "I


would hesitate to say that it would translate to physical violence," she


says.

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