Analysing the Hazards of Cannabis Use

We hear in the media how cannabis is great for hundreds of maladies from insomnia to acne. That it “cures” many different diseases including incurable brain tumors, and stage four cancers. Sadly, hard evidence of these “cures” are still lacking. Internet searches produced the occasional anecdotal case study showing that marijuana indeed provided treatment, it seemed to induce a remission in some cases of end-stage cancers and other grave diseases. And I have written up nearly every high-quality case study available, which comes out to maybe 12 cases.

Only one of these was found in a peer-reviewed journal, but it clearly showed a powerful dose-response using cannabis in treating leukemia.


But one needs to ask, if marijuana is such a powerful treatment for end-stage cancers, why is there no clinical data, and little anecdotal data, available supporting this assumption? Where are the thousands of cases that should have made it to the media by now supporting the role of cannabis as a successful treatment?

Clinics in Colorado and the Bay Area of San Francisco are making astonishing claims. They are all patting themselves on their backs informing the world of dozens, no hundreds, of cannabis “cures” but they provide absolutely no proof supporting such claims. If there is no proof, then it didn’t happen.

Remember for every outrageous claim of a successful cannabis treatment, equally powerful proof must be available.

So far, I have not seen sufficient proof. Perhaps this will change when those who are (allegedly) doing the “curing” come forth and provide us with well written, anecdotal case reports.

The paucity of case studies (even simple anecdotal ones) reinforces the notion that perhaps marijuana isn’t all it’s cracked up to be.

The biological data (animal, cell culture) is pretty abundant but human clinical trials are sparse, as can be expected due to marijuana’s criminal classification nearly worldwide. Several EU nations and Israel have recently relaxed their attitude on cannabis and have begun clinical trials. But in every case there still isn’t much to go on.

But don’t most of these studies show that cannabis is basically harmless? Well, that depends on what aspect you are examining and who you are speaking to. Many will insist that marijuana is completely safe — as safe as an almond oil rubdown.

But no drug is completely safe and even cannabis has its problems. Some insist that there exist numerous health and safety issues regarding the chronic use of marijuana — that the mainstream press have glossed over, while soft-peddling any serious discussion.

This article will try to unravel fact from fiction based on scientific evidence where available.


Take Colorado for example, what’s the fallout so far from legalization?

Colorado legalized cannabis in January of 2014. Since then, many will tell you that it has been a smashing success. It is a nearly one-billion-dollar operation, already, in just two short years. From the Boston Globe:

The consensus among several top state officials…is that there have been no widely felt negative effects on the state since marijuana became legal, and a crop of retail stores, cultivation facilities, and manufacturers sprung up from Aurora to Telluride.

Legalization has ushered in thousands of new jobs in the burgeoning industry, brought $135 million into state coffers last year, and ended the prohibition of a widely used substance.

But police say they struggle to enforce a patchwork of laws covering marijuana, including drugged driving. Officials fret about the industry becoming like big tobacco, dodging regulation and luring users with slick advertising. And this state,…has the highest youth rate of marijuana use in the nation, according to the most recent data available from a federal drug-use survey.

How do top officials from the state of Colorado feel about legalization after two years?

“There are a certain number of folks, like myself, who were pretty reticent about it to begin with”, said House Speaker Dickey Lee Hullinghorst, a Democrat. But the sky didn’t fall. Everything seems to be working pretty well.

Recent surveys of Colorado residents show that 53% believe legalization has been good for the state. Dr. Larry Wolk, the top medical official in Colorado’s public health department, said that since legalization, no large troubling public health trends have cropped up yet, save for sporadic reports of drugged driving and overdosing on edibles.

One of the biggest problems says Dr. Michael DiStefano, who directs emergency medicine at a pediatric trauma center: is the inability of kids to distinguish between normal products and those infused with THC. Thus, children may overdose on these medications, which totalled 15 cases last year (2015).

The biggest concern for those who opposed legalization is the ‘normalization’ of marijuana and accessibility, as it becomes ever easier for under-age kids to procure THC based drugs.

But as far as Colorado is concerned, they started out with a high percentage of youths using cannabis before legalization, and it has stayed high; but the percentages of kids using cannabis have not increased since legalization.


Let’s examine some observations of Dr. Christian Thurstone from an online article featuring Dr. Madras, a professor of psychobiology at Harvard Medical School’s Department of Psychiatry, and world authority on drug addiction, summarizing the current data on some of pot’s less desirable findings.

Take a look at Professor Madras’ compilation, and it should become obvious fairly quickly that marijuana is addictive, harmful (especially to the developing adolescent brain), and proponents of its legalization are working intentionally to dupe millions of people.

  1. Does heavy cannabis use adversely affect your life?

A study published in 1997 by Veterans Affairs doctors demonstrated that heavy cannabis use does not cause socio-economic problems. However, newer information suggests that heavy cannabis use can adversely affect many aspects of life.

Two groups were compared: those who were heavy cannabis smokers versus those who had used cannabis only sparingly if at all. The results found no significant differences:

…between the two groups on reported levels of income and education in their families of origin. However, the heavy users themselves reported significantly lower educational attainment…and income… than the controls,… When asked to rate the subjective effects of cannabis on their cognition, memory, career, social life, physical health and mental health, large majorities of heavy users (66-90%) reported a “negative effect.” On several measures of quality of life, heavy users also reported significantly lower levels of satisfaction than controls.

Further corroboration comes from a 2009 Lancet publication where they listed some of the adverse effects of chronic cannabis use:

…dependence (addiction) syndrome (in around one in 10 users); chronic bronchitis and impaired respiratory function in regular smokers; psychotic symptoms and disorders in heavy users, especially those with a history of psychotic symptoms or a family history of these disorders; impaired educational attainment in adolescents who are regular users; subtle cognitive impairment in those who are daily users for 10 years or more.

         2. Cannabis and driving.

The conclusions here might seem obvious. Many already know that smoking cannabis and operating heavy machinery do not necessarily go hand in hand. From a series of publications, several in the highly respected, peer-reviewed medical journal, the British Medical Journal (BMJ) and others reported:

Risks for motor vehicle accidents are higher. Acute cannabis consumption is associated with an increased risk of a motor vehicle crash, especially for fatal collisions. Another study demonstrated a concentration-dependent crash risk for THC-positive drivers. Alcohol and alcohol-drug combinations are by far the most prevalent substances in drivers and subsequently pose the largest risk in traffic, both in terms of risk and scope.

         3. Cannabis and IQ.

Can the chronic use of cannabis lead to decreases in mental function and intelligence? One study completed in 2012 did show decreases in neuropsychological functioning among cannabis smokers from adolescence to age 38. The more they smoked, the greater the decline. Some of this appeared to be irreversible, this led the authors to declare:

Findings are suggestive of a neurotoxic effect of cannabis on the adolescent brain and highlight the importance of prevention and policy efforts targeting adolescents.

Overall brain function and executive function are decreased during acute intoxication with marijuana. There are many studies which demonstrate this effect. Most people understand that’s what cannabis is expected to do as an intoxicant. The most common side effect is the temporary decrease in short-term memory, while intoxicated.

          4. The use of cannabis and the development of psychosis.

Compelling data exist that children who start very early using cannabis, and have a family history of psychotic illness, may indeed develop their illness at an accelerated rate. These kids should completely avoid cannabis. If you fall into this category you could develop your first psychotic break nearly three years earlier than if you had never used cannabis. The results of a meta-analysis showed:

…evidence for a relationship between cannabis use and earlier onset of psychotic illness, and they support the hypothesis that cannabis use plays a causal role in the development of psychosis in some patients.

          5. Does cannabis use promote cancers?

That question requires an entire article to accurately respond to but here’s several studies that suggest that cannabis does not cause cancer.

Researchers at the Kaiser-Permanente HMO, funded by NIDA, followed 65,000 patients for nearly a decade, comparing cancer rates among non-smokers, tobacco smokers, and marijuana smokers. Tobacco smokers had massively higher rates of lung cancer and other cancers. Marijuana smokers who didn’t also use tobacco had no increase in risk of tobacco-related cancers or of cancer risk overall. In fact their rates of lung and most other cancers were slightly lower than non-smokers, though the difference did not reach statistical significance.

Donald Tashkin, a UCLA researcher whose work is funded by NIDA, did a case-control study comparing 1,200 patients with lung, head and neck cancers to a matched group with no cancer. Even the heaviest marijuana smokers had no increased risk of cancer, and had somewhat lower cancer risk than non-smokers (tobacco smokers had a 20-fold increased lung cancer risk).

Dr. Tashkin has shown from above and other studies that cannabis may have a protective role for COPD and in some cancers.

As far as head and neck squamous cell carcinoma (HNSCC) risks are concerned, the author (Dr. Thurstone) correctly states:

At this point the majority of studies do not support the hypothesis that smoked cannabis is strongly associated with an increased risk of HNSCC, once tobacco and alcohol intake are controlled, though smoked cannabis may raise the risk of HPV-16-associated HNSCC.

Another very large study also revealed that cannabis use is not significantly associated with cancers of various types:

A study of 65,855 members of a U.S. health management organization (HMO) that classified member as experimenters (six or fewer lifetime usages), former users, or current users found no increased risk of HNSCC, lung, colorectal, melanoma, or breast cancers in current or former cannabis smokers versus never smokers or experimenters when controlled for tobacco use, alcohol intake, and socioeconomic status.

Others found cannabis associations with testicular cancer; an increase in lung cancer in a small North African study; a three-fold increase in prostate cancer risk among cannabis users; a nearly three-fold increase in primary gliomas (aggressive brain tumors) in people who smoked cannabis once per month or more.

Overall, the data collected as of 2016 does not implicate cannabis as a cancer inducer in the same way we view tobacco and alcohol.

Well, what about cannabis and the ability to fight cancer?

Keep in mind that one of the most valuable observations is whether or not cannabis anti-tumor effects, seen in lab animal studies, also translates to human studies.

Rather than only witnessing anti-tumor effects in petri dishes (cell cultures) and test tubes, we need carefully controlled human trials to prove cannabis is anti-cancer.

As far as human studies go we simply have very few clinical trials regarding cancer and cannabis.

Although there is accumulating data from test tube studies (cell culture), and some in living mice, there is scant, insufficient, inadequate clinical data on cannabinoid effects on cancer treatment in living humans.

Conclusions on cancer and cannabis:

  • Smoked marijuana is associated with increased risk for cancer, and not with potential as an anti-tumor agent.
  • Preclinical research demonstrates that some cannabinoids have anti-tumor activity.
  • The activity is mainly at the CB2 receptor, which has no psychoactive effects. Drugs selective for this receptor (and for other non- CB targets) may have a therapeutic role in tumor regression.
  • More preclinical research is needed, to define with precision, which class of cannabinoids will function and how genotypes may affect therapeutic benefit.
  • It is premature to surmise that cannabinoids will succeed as anti-tumor agents, until rigorous Phase III clinical trials in human subjects display therapeutic potential.

A few comments: the increased risk for cancers from marijuana use is weak. There are just as many epidemiological studies showing a protective effect or no association with cancer from cannabis use. The anti-tumor, anti-cancer effects of cannabis are by no means limited to the CB2 receptor.

In fact, it’s the opposite, which forms the basis for the ‘entourage effect’ which is the synergistic anti-cancer potential formed when all of the cannabinoids and terpenoids work together in an orchestrated symphony.

In summary, marijuana is not benign especially in adolescence, but it has also been shown to be much safer than other legal or illegal intoxicants. Bronchitis and anxiety in the novice, being some of the most common side effects of cannabis. And so far, it does not appear to be toxic to humans in any significant way.

Dr. Christopher Rasmussen
Dr. Christopher Rasmussen MD,MS, an anesthesiologist with a Master’s degree in traditional Chinese medicine, is a professor, lecturer, seminar provider, and world authority on preventive medicine.For more information on preventive medicine see


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