Marijuana – The Truth – Part 4

In the book that I co-wrote with my good friend, Donal O’Mathuna, Ph.D., Alternative Medicine: The options, the claims, the evidence, how to choose wisely, we wrote an evidence-based article on marijuana. Here’s our fourth excerpt of that information.

In earlier excerpts, we discussed “What It Is,” “The Claims People Make about Marijuana,” and “Study Findings.” In this excerpt, we’ll discuss, “Cautions.” Next week, our final excerpt will review “Our Recommendations.”


Advocates of medical marijuana point out that no one has ever reported a lethal overdose from marijuana. Estimates based on animals have put the amount needed to kill someone at about 20,000 times the amount normally used medically. This compares with some drugs whose lethal dose is only a few times the amount commonly prescribed.

While this may be the case, it would be analogous to claiming that since few people die from an alcohol overdose, no serious problems arise with the use of alcohol below its toxic levels.

Marijuana use can lead to problems after both acute and chronic use. The high for which marijuana is used recreationally has many similarities to intoxication. A 2005 study of car accidents in France found that the chances of drivers being responsible for a fatality were more than three times higher if they had been using marijuana compared to those who had not. At least 2.5 percent of fatal crashes were due to marijuana, compared to 28.6 percent due to alcohol use.

Marijuana leaves people sedated and less coordinated, making it unwise to drive or operate equipment while under its influence. Coordination problems may last up to 24 hours, long after the person no longer feels high.

Many people report euphoria and positive feelings from the high, but 40 to 60 percent report unpleasant experiences. This has been the case with marijuana smoked for medical reasons, with sublingual sprays of marijuana extracts, and with Marinol.

About 10 percent of regular recreational users of marijuana develop dependence, according to the Royal College of Physicians’ report. When people stop using marijuana after chronic use, they can have withdrawal effects, with symptoms like restlessness, insomnia, nausea, and cramping.

Compared to other abused drugs, these can be mild and short-lived.

The IOM report found no conclusive evidence that marijuana is a “gateway” drug. The frequent finding that users of illicit hard drugs report having earlier used marijuana can be explained by marijuana being so commonly used. Underage tobacco smoking and alcohol drinking act as “gateway” drugs just as much as marijuana.

The 2005 survey in the United Kingdom also identified reduced time spent with parents and increased time spent with drug-using peers as the most significant factors leading to teenagers’ use of illegal drugs. At the same time, no evidence counteracts the fear that allowing medical use of marijuana might lead to greater illicit use.

Other physical effects of smoking marijuana are of significant concern. All-out efforts are under way to reduce tobacco smoking because of its widely acknowledged dangers. Marijuana smoke does not contain nicotine, but has a significantly higher tar content that is usually not filtered, except when water bongs are used.

The first study to conclude that marijuana smoking puts people at higher risk for cancer was published in December 1999. This epidemiological study compared the rate of marijuana use among adults with head and neck cancer to similar people without cancer.

The researchers found that after they made allowances for other risk factors like smoking cigarettes and alcohol, those who had used marijuana at any time had 2.6 times the risk of these cancers compared to those who never used marijuana. However, later studies have not found any increased risk of these cancers from smoking marijuana.

Similarly conflicting results have been published from other epidemiological studies of marijuana and lung cancer risk—although clear evidence of lung damage is visible. Marijuana smoke contains carcinogens, but it also contains compounds that have been found to prevent the spread of cancercells in laboratory tests.

At this point, it is unclear how marijuana affects someone’s risk of cancer, although there are good reasons to be concerned about the connections.

Other negative effects have been reported. Students regularly using marijuana have lower grades, more traffic accidents, higher use of alcohol and sex as coping mechanisms, and more psychiatric problems than nonusers. These conclusions come from epidemiological studies that do not establish cause and effect, but have been cited as evidence of what is called “amotivation syndrome.”

More seriously, there is growing evidence of a connection between marijuana use and psychosis. Cannabis can precipitate psychosis and continued cannabis use in psychotic patients makes their illness worse. The relationship between the two is complicated, with considerable debate over whether marijuana causes psychoses or whether people with psychosis tend to experiment with marijuana.

The evidence is moving toward a consensus that daily use of marijuana causes psychosis and precipitates schizophrenia, especially if use begins before age 15. A study in New Zealand monitored marijuana use in people for 25 years and published its results in 2005. It found that daily marijuana users had a 1.6 to 1.8 times greater chance of developing psychosis even after all other known causes were taken into account.

Evidence from animal and brain studies has shown a connection between the natural cannabinoid system in the brain and the neurotransmitters believed to be involved in psychosis, though much remains to be learned here .

Other concerns have been expressed that marijuana may negatively impact the immune system, increasing the risk of infection. This would be particularly problematic since the people for whom medical marijuana is most frequently recommended (AIDS and chemotherapy patients) are already at very high risk for infections. Research is not as yet clear about this connection.

The Natural Database rates marijuana as “possibly unsafe” for adults and children, “unsafe” in pregnancy, and “likely unsafe” (orally or inhaled) for breast-feeding women.

Here’s the entire series:

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