What smoking pot does to the body
Thursday, September 26, 2002
Herald News Services
Scientists from as far away as Britain and Japan attended a conference in Banff this year hosted by the Canadian College of Neuropsychopharmacology, an umbrella organization of researchers who study the impact of drugs -- recreational and medical -- on the brain.
The sessions attracted a few of the world's leading psychopharmacologists, whose research reveals that some of our attitudes towards mood-altering substances are not only hypocritical, but absurd.
Marijuana, characterized for decades as a wicked corrupter of youth, is now known to have tremendous potential to treat pain and illness, and is far less harmful than such longtime legal drugs as alcohol or tobacco.
"Cannabis is essentially a good drug with a bad reputation," said Dr. Peter Silverstone, a psychopharmacologist and clinical psychiatrist from Edmonton who helped organize the Banff conference.
While polls reveal Canadians are split on the question of legalizing marijuana -- about 47 per cent for and against -- the pro side has gone up from about 30 per cent in the mid-1970s and the mid-1990s.
The Canadian Police Association, however, describes marijuana as a dangerous "gateway" drug that entices people to use harder drugs such as cocaine. But, if you ever wanted to find a medically beneficial, mood-
enhancing, mostly benign substance, marijuana is your drug.
"THC is probably one of the safest compounds on Earth," said Daniele Piomelli, a psychopharmacologist from the University of California at Irvine.
It was only in the last decade -- 1992 to be exact -- that scientists were able to definitively locate the systems in the brain affected by cannabis. It's now known that naturally occurring chemicals, known as endocannabinoids, trigger pleasure centres in the brain, in much the same way dopamine does.
But cannabis is far less toxic on the physical structure of brain and doesn't have the addictive properties of other drugs. "Cannabis . . . doesn't have that command over your personality that nicotine, cocaine or alcohol have," said Piomelli.
"The effects of THC and alcohol are completely different," said Piomelli. "Alcohol is way more toxic than cannabis -- it is devastating to your liver and devastating to your brain."
Then there is the medical potential of marijuana. The two cannabis researchers say marijuana has proven effective in regulating pain -- better than morphine in many respects -- boosting appetite, controlling nausea, even reducing tremors in sufferers of multiple sclerosis. There is also evidence cannabis derivatives have anti-stroke, "neuroprotective" properties.
Smoking marijuana several times a week leaves a lasting effect on a healthy person's immune system, a new study from Florida says. But this may actually boost opportunities for the medical use of marijuana.
The effect of marijuana smoking suppresses the immune system by altering the molecules on the outside of some of our cells, and suppresses inflammation at the same time.
This could be a useful tool in combatting diseases where the immune system runs out of control and causes painful, and sometimes dangerous, inflammation in our bodies, say scientists at the University of South Florida and the University of California, Los Angeles (UCLA).
Arthritis is the most common form of inflammation caused by a misdirected immune system. By attacking our healthy tissue, it causes inflamed and sore joints.
Now Thomas Klein, a professor of medical microbiology and immunology at South Florida, says marijuana may do a similar job.
His study of 10 healthy marijuana smokers, all of whom smoked at least several times a week, and 46 non-drug users found molecules called marijuana receptors were more numerous on marijuana smokers' white blood cells, part of their immune system.
The findings were reported recently in the Journal of Neuroimmunology.
Marijuana's influence on the immune system has been hotly debated. While there's a lack of information on humans, Klein says animal studies show that marijuana and its psychoactive compounds, known as cannabinoids, suppress immune function and inflammation.
"This suggests marijuana or cannabinoids might benefit someone with chronic inflammatory disease, but not someone who has a chronic infectious disease such as HIV infection," he said.
If that's true, "this property might be harnessed to treat patients with overly aggressive immune responses or inflammatory diseases like multiple sclerosis and rheumatoid arthritis.
"The bottom line is you cannot routinely smoke marijuana without it affecting your immune system," he said.
For a long time, nobody knew what delta-9 tetrahydrocannabinol (THC -- the active ingredient in pot) was doing in the brain because there didn't seem to be a receptor for it. Only in the last 10 years did scientists finally find the receptor and isolate a naturally occurring brain chemical called anandamide that binds to it, notes the National Institute on Drug Abuse (NIDA)
THC also binds to the anandamide receptor and suppresses activity in the hippocampus, an area of the brain pivotal for learning, memory and emotions. Studies show that learned behaviours deteriorate with marijuana use. That translates to problems with attention, memory and learning -- all of which are impaired among college students who use marijuana heavily, even after they have stopped using the drug for 24 hours.
On average, it takes at least 30 hours for the body to clear even half of the THC from a single use.
Those who begin using marijuana before college show lower achievement and are more likely to engage in more delinquent behaviour and aggressiveness than non-users.
There also are lots of anandamide receptors in the basal ganglia and cerebellum, both of which are involved in movement control, and in the cerebral cortex, where the "high" probably is generated.
Other physical effects:
n In the lungs, marijuana produces many of the same health effects as tobacco smoke -- daily coughs, phlegm, chronic bronchitis and increased susceptibility to chest colds. Long-term marijuana use damages lungs.
n Since marijuana smokers inhale deeply and hold the smoke in their lungs for long periods of time, they also appear to be exposed to three to five times the levels of carbon monoxide as tobacco smokers. Marijuana increases heart rate and raises blood pressure.
n Like nearly all drugs, marijuana doesn't mix with pregnancy. Use of marijuana by expectant mothers raises the risk of delivering a baby who has a low birth weight and is at increased risk for various health problems.
n Nursing mothers who smoke marijuana pass THC to their babies through breast milk and risk damaging their infant's motor development. Children who breathe passive marijuana smoke display more temper tantrums, thumb sucking and anger than youngsters not exposed.
Current and past smokers of marijuana are at increased risk of developing cancer of the head and neck, including tumours of the mouth, throat and larynx, a study found last year.
The study, the first to link marijuana with such cancers, suggests that the drug's popularity in recent decades could have serious long-term health consequences for some users.
Marijuana smoke is higher in tar and carcinogens than tobacco smoke, and previous research has shown that marijuana smokers, like cigarette smokers, can develop precancerous changes in cells lining the respiratory tract.
Researchers said they therefore were not surprised at the news that smoking marijuana predisposes users to head and neck cancers, and they predicted it will likely be found to increase the risk of lung cancer as well.
"It's what I expected to see," said Li Mao, an associate professor of medicine at M.D. Anderson Cancer Center in Houston. "It appears marijuana (smoke) is a stronger carcinogen than cigarette smoke."
Nevertheless, the independent effect of cigarette smoking on an individual's cancer risk is probably greater than that of smoking marijuana, noted Eugenia Calle of the American Cancer Society, "because people just smoke so many more cigarettes."
Many doctors believe marijuana can be helpful in the treatment of people with cancer and AIDS. Starting in the 1970s, studies have shown that oral doses of marijuana's major active ingredient, delta-9-tetrahydrocannabinol, or THC, alleviates the nausea and vomiting caused by chemotherapy. The drug, also called dronabinol or Marinol, was approved by the Food and Drug Administration in the U.S. for this purpose in 1985.
A 1988 study by Cornell University researchers found that smoking marijuana was even more effective than the oral medicine. It relieved nausea in 44 of 56 patients who hadn't responded to other anti-nausea treatments, including some who had failed to respond to oral THC.
Marijuana's ability to stimulate appetite is also well established. The FDA approved oral THC for the treatment of AIDS-related anorexia and weight loss in 1992, based on evidence from a study involving 139 AIDS patients who were randomly assigned to receive either THC or a placebo.
Appetite increased significantly in the THC-treated patients. Side effects such as dizziness, sleepiness, confusion or feeling "high" occurred initially in 18 per cent of the THC-treated group, but they decreased when the dose was lowered or the medicine was taken late in the day.
Despite the drug's popularity among AIDS patients, some experts are worried about research that suggests that marijuana suppresses the immune system, and about the bacteria, fungal spores and lung-damaging chemicals present in marijuana smoke.
Donald P. Tashkin, a professor of medicine at the University of California, Los Angeles, said some studies have linked marijuana use with opportunistic lung infections and with more-rapid progression of HIV infection.
"The downside is that (smoking marijuana) might increase the risk of developing pneumonia," he said.
Marijuana smoke contains some 420 chemicals, including twice as many
carcinogens as a tobacco cigarette of the same weight. Heavy marijuana
smokers frequently suffer from bronchitis, and they may eventually be found
to have an increased risk of emphysema or lung cancer.
© Copyright 2002 Calgary Herald