Marijuana is a drug which has been touted as one of the most effective remedies for migraine, the pain of arthritis, the sleep disorders of the elderly and even for heroin addiction. It has also been hailed as the basis for a highly profitable rural industry and the saviour of many farmers. On the other side, it has been condemned as addictive itself, morally corrupting, brain damaging and carcinogenic. Confused? Check out the information, then make up your own mind about marijuana.

For many of us, the image of the marijuana user is the hippy, the drop out, the fringe members of our community. But the reality is very different.

Two thirds of 20-year-olds have used marijuana and about one in eight of all adults. Marijuana use is everywhere. It's even in our own backyards.

One place where marijuana is on the menu is Amsterdam. "Some people just smoke one kind always," explains a waiter at one coffee shop. "It all just depends on your individual taste."

While we agonise over whether marijuana should be decriminalised, the Dutch have tried to diffuse the issue by turning a blind eye to some of the ways it's sold.

For more than half a century marijuana has been reviled as a dangerous drug. Yet at the same time as negative views about the drug were being propagated and widely accepted, marijuana users were saying that it was absolutely safe.

Today, the work of scientists is revealing that the truth lies somewhere in between.

The simple plant known to science as Cannabis Sativa is the cause of all the commotion. People have been growing it since well before Biblical times and along the way it's picked up many names. If you're extracting its fibres to weave cloth or canvas, it's called hemp. But when it's grown for the drugs, it's called cannabis or simply marijuana.

When you have a joint, you're inhaling burnt plant products. And the effects, according to pulmonary physiologist, Professor Donald Tashkin, are closer to tobacco than many users would like to think. "Hydrocyanic acid, oxides of nitrogen, aldehydes and phenols are very noxious chemicals and they are present in both marijuana and tobacco and in much the same quantity."

Tashkin's laboratory at the UCLA School of Medicine in Los Angeles, has a special interest in the effects of smoked substances on the lung. "Marijuana is smoked quite differently from tobacco," explains Tashkin. "It's smoked with a larger puff volume, the puffs are inhaled more deeply into the lungs and most importantly of all, I believe the smoke is held in the lungs about four times longer."

This, plus the fact that a marijuana cigarette is loosely packed and unfiltered explains why four times as much tar is inhaled (from a joint) as from a single tobacco cigarette.

With modern endoscopy, scientists have looked inside the lungs of marijuana-only smokers and found that the bronchial tubes appeared red and swollen. Tashkin warns the occurrence of malignancy is a possibility.

"We were able to detect the over expression of genetic markers that are linked to the development of lung cancer in the marijuana plus tobacco smokers."

Professor Wayne Hall from the National Drug and Alcohol Research Centre concurs:

Lung cancer is not as clear because we haven't had as long a period of observation to observe marijuana smokers heavily but I think it's reasonable to predict that some people who smoke marijuana regularly over many years, perhaps decades, will develop lung cancer as a result.

And just in case you're wondering, research reveals the lungs won't be any better protected using a bong or water pipe.

But what about the effects of marijuana on the brain? The brain effects are produced by chemicals unique to the marijuana plant and in particular tetra hydro cannabinol or THC. It dissolves in fat, a property which is put to good use when people bake with cannabis the famous hash cookies. The key ingredient is the "butter", a mixture of marijuana leaves and regular butter that's been covered in water and allowed to simmer for a few hours.

Since THC has an affinity for fat, it's stored in the fat in your body. And whether you eat it or smoke marijuana, this fat solubility, according to pharmacologist Professor Billy Martin from the Medical College of Virginia, means that the effects of THC linger longer than you'd think.

"It can stay in brain cells for several hours and so one usually has a somewhat slow onset of action but a long duration of action."

Dr Nadia Solowij is a research psychologist at the National Drug and Alcohol Research Centre in Sydney. She and her team are running a "quit" program for marijuana users. Part of this work involves research looking at cognitive function, specifically attention and information processing, in long-term marijuana users. "A lot of cannabis users," recalls Solowij, "came to us saying, 'I can't quite put my finger on it. I know that I'm not doing particularly well, but I'm not sure what it is. I think my memory's been affected.'"

Solowij has studied the brain effects of heavy marijuana useage. She measured brain wave responses to certain stimuli and found that those smoking more than three times per week processed information more slowly and had trouble with decision-making. Solowij continues:

We assume that that kind of slowing of information processing is due to there constantly being THC present in the body even when the person is not necessarily stoned. So we predict that if a person was to cut down on the frequency with which they smoke marijuana to say less than once a week, that kind of slowing of information processing would improve.

She also tested the marijuana smokers' ability to focus attention and filter out information they didn't need, and found that this was poorer in long term users. "Because that was related to duration of cannabis use, it suggested that there may be gradual changes occurring in the brain as a result of cumulative exposure to cannabis."

But these are subtle changes in the brain and nothing like the damage you'd find with heavy, long term alcohol users:

My old man's a smoker,
Like blokes are meant to be,
He don't come home at night
Cause there's something wrong with me...
(There's something wrong with her.)

With seven kids to care for,
The cleaning keeps me workin'
I'm glad I've got my tablets
And I'm pickled as a gherkin.
(She's pickled as a gherkin.)

I take Valium, Prozac, Serepax, Aropax, Mogadon and .. and Rohipnol,
And Nydactil.

What about cannabis?
..... No I don't do drugs!


We now know that cannabis works quite differently to drugs like alcohol and cocaine. Whereas the latter actually disrupt parts of the brain, cannabis apparently plugs right into a unique set of receptors. These cannabinoid receptors (as they've been called) have been discovered throughout the brain (and much of the body too). It's as if we're all "pre-wired" to get high on marijuana! But how could that possibly be?

The discovery in 1992 of a strange-looking molecule solved the mystery. It's a brain chemical no one previously knew about. This is what all those cannabinoid receptors are really there for. It's been appropriately christened "anandamide". That's Sanskrit for "eternal bliss". Martin is puzzled. "This really raises somewhat of a dilemma. If we have this naturally occurring cannabinoid system, then why don't we just walk around and get high? I mean we're asking, what is it doing?"

Anandamide is still a mystery substance but we're starting to figure out what its purpose is. The brain probably releases it to calm us down when we're really anxious about something. It makes us feel mellow, dulls pain and dampens the edge of unpleasant memories, just as marijuana does.

The reason marijuana's effects are more extreme is that it floods the brain in much higher concentrations.

Recently evidence has appeared that heavy marijuana use not only swamps the anandamide system but over a long time, it can make the user dependent on it. Hall is cautious:

I don't think you should exaggerate the risk. I certainly wouldn't want to create the impression that everyone that uses marijuana will become dependent. But certainly it's not a trivial risk. There's roughly a one in 10 chance.

One user, Natalie, maintains she's always in control. "It's just become a habit for me, " she says:

When I get stressed or when I'm in situations that I can't handle, I smoke some pot. I never let it get out of hand, and always give myself a break from it so that it doesn't become a habit, or a tool that I use to solve all my problems.

Another user, Murray, can also take it or leave it:

Compared to cigarettes, I find marijuana far less addictive. I've just given up smoking for the one hundredth time, I know how hard that is. Dope is also less damaging than alcohol, at least in larger quantities, so for me it's a preferable drug.

But the fact is that some people do feel dependent on marijuana. This was confirmed when a proposed treatment study by Solowij and her husband, Dr Brin Grenyer, was swamped with volunteers. According to Grenyer:

The typical profile was somebody who was married with kids, who was working every day and who felt like they weren't up to scratch like they used to be. They felt more dependent on the drug, they felt like their work was suffering and they felt like they needed help.

The existence of marijuana dependence is supported by animal research.

After rodents have been given THC, the active component of marijuana, they behave as if they're zonked out.

But after they've been given another drug which blocks the action of THC, the animals become overactive and show clear signs of withdrawal - as if their hair is standing on end or they've got the shakes!

When people quit, they don't get such dramatic symptoms because their THC levels drop very slowly. That's an important difference, says Martin, between marijuana and the opiate drugs like heroin:

Most marijuana smokers probably don't smoke to the extent that they become dependent. Clearly the dependence that marijuana would produce would certainly be much milder than it would be with opioids, it's not a strongly, profoundly, dependence producing substance.

Dr David Halliwell is a general pracitioner on the NSW north coast, a centre for heavy marijuana useage. He's found dependence on marijuana much easier to treat than nicotine or alcohol addiction:

The withdrawal symptoms that you see with cannabis tend to be mild, they tend to be transient and last only a few days before they settle down. After that, as long as they're managing their stress, people generally don't experience a hard degree of craving. Whereas with nicotine, you'll encounter ongoing craving and ongoing relapse far more often. Of course with alcohol withdrawal, that can actually be a medically dangerous situation with withdrawal fits or the DTs.

But the fact that cannabis can stimulate the craving centres in the brain may have a medical use, because marijuana provokes a craving for food, the so-called "munchies". AIDS sufferer, Claude, is losing weight because he never feels like eating. So he uses marijuana to stimulate his appetite. "I take 30 or 40 tablets a day and the dope just helps me to make sure that I graze, what I call graze, so that I just continue to eat."

But the other reason Claude takes marijuana is to quell the nausea caused by some of his medications. He finds it works well but marijuana's illegality makes his life harder than it needs to be. "I think it's cruel and inconsiderate that people are not given the opportunity and the choice to make up their own mind," he laments.

Claude's not alone. Richard Brookhiser is a conservative political journalist in the United States who now advocates the legalisation of marijuana for medical uses. In his case, he was having chemotherapy for testicular cancer and found that the available anti-nausea drugs weren't as good as marijuana. "With the pills, it takes half an hour to feel an effect and you can't control the dose effectively whereas with the smoked marijuana, you get the effect in five minutes plus it's very easy to regulate it yourself."

Brookhiser continues:

None of the oncologists or nurses said 'don't do this' or 'this is a bad idea'. All had had patients who'd used it and reported good effects in treating nausea. But the thing was, they couldn't give it to me themselves because it's illegal, like heroin is. They couldn't prescribe it so I had to break the law to get it!

Some studies have verified that cannabis can provide relief from nausea, pain and muscle spasms and alleviate symptoms of glaucoma, multiple sclerosis, AIDS, migraine, epilepsy, depression, PMT and other debilitating ailments.

It should come as no surprise that cannabis has been taken as medicine for centuries yet science has been reluctant to endorse it as a therapeutic drug. The fact is it's hard to study because it's illegal.

Marijuana leaf

But it hasn't always been illicit. In fact, the old anti- marijuana propaganda films were made to scare people at a time - paradoxically - when cannabis was perfectly legal.

Father and son, Harry and Geoff Boyle are farmers and remember this period in the sixties well. "You could buy marijuana by the hundredweight," recalls Harry. "And they used to advertise hashish cigarettes for asthma. I could show you back copies ofThe Mercury where it was advertised quite freely and nobody wanted it."

But soon they did want marijuana - because the negative publicity probably whetted young people's appetite for forbidden fruit. "Suddenly it was the 'in' thing," says Harry. "Everybody was chasing it and it became known as the sex drug even though it had no effect on sex or for that matter, anything else. It just lowered inhibitions."

Thirty years ago in the Hunter valley, it didn't take much to generate hysteria after the discovery of vast amounts of cannabis weed growing naturally along the river bank. "I broke a branch off," Geoff remembers, "and gave it to my father. The next time he went into town, he took it to the Department of Agriculture to find out what it was."

Harry picks up the story:

There were dairy farmers all along the river and the people in Sydney were drinking milk laced with marijuana. I don't know what it did to them but it never ever did anything to the cows. It was my only chance of ever becoming a millionaire.

Many people believe that marijuana is a stepping stone to harder drugs. Yet there is no biological evidence that this is the case. Certainly, when rats that are on cannabis are offered heroin or cocain, they show no more interest than rats that have never tasted cannabis in their lives. Martin is unequivocal. "I don't know of any evidence that one particular drug will actually cause an individual to use another specific drug later on."

It's this issue, more than any other, that seems to colour people's opinions about marijuana - namely whether or not it leads to harder drugs. And while biology is not to blame, there is, says Hall, a social link:

People who get heavily involved in marijuana expose themselves to a market and to social groups in which a lot of those other illicit drugs are used and probably are encouraged and that increases their chance of experimenting.

In The Netherlands, they've been trying to prevent marijuana users coming into contact with the pushers who sell heroin. They haven't legalised marijuana, nor do they think it's an entirely safe drug. But by tolerating its sale under strict guidelines rather than driving it underground, they're making it less desirable for adolescents. "In fact, we don't believe it's very attractive anymore for the young to buy cannabis because it's more or less tolerated," says Bob Keizer, who's with the Ministry of Health in The Netherlands:

If we study the careers of the average cannabis user, they start using it when they're 15, 16, maybe 17, then they stop. The majority just stop using it. So in our system, the so-called marginalisation of the cannabis user can be prevented.

Nor has there been an explosion in heroin use. In fact, there's some evidence that a declining number of young people in The Netherlands are taking up heroin. "The number of hard drug users has been stabilised for more than 10 years in the Netherlands," confirms Keizer. "It's a low figure compared to other countries. And also the fact that this number has been stabilised for more than 10 years indicates that our policy is successful on this point."

Marijuana is not the completely safe drug that many of its advocates say it is. Long term use can damage the lungs, affect the brain in subtle ways and produce a form of dependence. But it's still not as toxic as tobacco or alcohol. Yet marijuana's illegality limits the sort of health advice and health care that should be available. "It's made it difficult," admits Hall:

to get messages out that are credible because many young people assume that any information about health effects are propaganda in favour of the continuation of the prohibited status of the drug. So for all of those reasons it's been very difficult to get out some reasonably balanced factual information about the drug's probable health effects.

We all choose one poison or another for ourselves. The trouble arises when the drug's legal status may cause more harm than its effects on the body.

Clearly, the marijuana debate is far from over.

ABC Online
© 1997 Australian Broadcasting Corporation