Pubdate: Sun,  6 Jan 2002
Source: San Francisco Chronicle (CA)
Section: Insight, Page D-3
Copyright: 2002 Hearst Communications Inc
Contact:  http://www.sfgate.com/chronicle/
Details: http://www.mapinc.org/media/388
Author: Susan Greenfield
Note: Susan A. Greenfield, the Fullerian Professor of Physiology at Oxford 
University, is director of the Royal Institution of Great Britain. This 
article was written for Project Syndicate, based in Prague.

Addictions

WHY THEY CALL IT 'DOPE'

Pot Really Can Blow Your Mind

Oxford, England -- Across Europe and America, the legalization of cannabis 
for personal use generates intense debate.

Britain has, to all intents and purposes, practically decriminalized 
marijuana usage.

As a neuroscientist, I am concerned. One common justification for 
legalization or decriminalization of cannabis centers around the idea that 
it does not involve a victim. At least four reports in major medical 
journals -- Ramstrom (1998), Moskowitz (1985), Chesher (1995) and Ashton 
(2001) -- show the contrary.

Costs to the community include accidents at work or at home, educational 
under-attainment, impaired work performance and health-budget costs.

Another argument is over that cannabis is nonaddictive. Of course, defining 
addiction is hard. But if one regards it as an inability to give up, then 
there is strong evidence that cannabis incites dependence. Recent 
scientific papers report many users in the United States, United Kingdom 
and New Zealand now seek treatment for dependence. Other papers show that 
10 percent of users want to stop or cut down but have difficulty doing so. 
A paper in 1998 reported that 10 to 15 percent of users become dependent on 
pot.

It was shown recently that withdrawal symptoms were experienced after only 
three days of light use. Heavy users confront a worse situation. Dr. Bryan 
Wells, a rehabilitation expert, says that for the first time he's beginning 
to see in heavy cannabis users the withdrawal symptoms produced by hard drugs.

Another argument is the beneficial effect of marijuana on pain. So far, 
that evidence is anecdotal; it is hard to exclude placebo effects. The 
results from clinical trials are awaited.

But distinctions should be drawn between recreational drugs and medicines, 
as they are for opiates. If cannabis is a painkiller, then it must have a 
huge impact on the physical brain.

Indeed, widespread reports exist of the impact of cannabis on the brain, in 
particular areas concerned with memory (hippocampus), emotion (mesolimbic 
system) and movement (basal ganglia). Cannabis affects a variety of 
chemical systems and it works via its own receptor -- its own molecular target.

The fact that there is a naturally occurring analog of cannabis in the 
body, as there is for morphine, provides a basic reason to differentiate it 
from alcohol.

For an agent that affects a variety of transmitter systems, it is as though 
it were a transmitter itself. This is not surprising, for cannabis has a 
clear effect on psychology. Not only does it produce euphoria, but the 
effects, often overlooked, may also include anxiety, panic and paranoia. 
Disorders in psychological performance, attention impairments and memory 
deficits are well known.

More disturbing -- and less frequently acknowledged -- is the fact that 
these effects can be long-term.

In one recent study, the attention spans of ex-users were compared to those 
of current users, short-term and long-term. The abstainers, who had been 
users for at least nine years, had quit from three months to six years 
before the study. Of the current users, one group had at least 10 years of 
dependence; the other, about three years. Everyone in the study had used 
cannabis from 10 to 19 days per month.

Although the quitters did better than users, all had attention impairments 
in comparison with nonusers in a control group. The impairment was related 
to the duration of use. Most disturbing was the fact that no improvement in 
performance occurred with increasing abstinence.

It was no surprise, then, that because these long-term effects seem to be 
irreversible, there is an effect on brain pathology. Because much of this 
data comes from work with isolated systems, and therefore on all brains, an 
obvious criticism is that you can't extrapolate from such data. Yet, the 
evidence suggests that the long-term effects must have a physical basis. Is 
there a safe dose of cannabis, with no effect on the brain? Even a dose 
comparable to one joint, and analogous levels of the active THC ingredient 
to that in plasma, can kill 50 percent of neurons in the hippocampus (an 
area related to memory) within six days. People are unaware that the THC in 
cannabis remains in the body for more than five days. For someone using 
cannabis routinely, the dose carried in the body is higher than they 
imagine. It is easy to underestimate the dose because of the wide range in 
the strength of cannabis. Individual variations in body fat and, 
worryingly, variations in one's disposition to psychosis, mean that you 
cannot predict how much cannabis will affect any person at any time.

Cannabis could well be having a serious effect on the mind, which I define 
as the personalization of brain circuits that reflect an individual's 
experiences. A transmitterlike substance, with such powerful effects, must 
affect those circuits. So blowing your mind might be exactly what marijuana 
users are doing.
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MAP posted-by: Beth