Health Risks of Marijuana Still Not Nailed Down… really?

A new article on MedPage today claims that we still don’t fully understand the health risks of cannabis use:

Overall, “the public health burden of cannabis use is probably modest compared with that of alcohol, tobacco, and other illicit drugs,” Australian researchers reported in the Oct. 17 issue of The Lancet.

Wayne Hall, PhD, of the University of Queensland in Herston, Australia, and Louisa Degenhardt, PhD, of the University of New South Wales in Sydney, reviewed nearly 100 studies covering acute as well as chronic effects of marijuana, including reports of the prevalence of marijuana use around the world.

Globally, they wrote, about 3.9% of the world’s population used marijuana in 2006, according to United Nations statistics.

Well it opens nicely by noting that cannabis is safer and that almost 1 out of 25 people worldwide use cannabis. It gets a bit dicey from there:

They spent more time detailing the psychomotor impairments associated with the marijuana high. “Some experimental studies have shown diminished driving performance in response to emergency situations,” Hall and Degenhardt said, findings also corroborated in epidemiological studies.

For example, one study of car crash victims found that they were more likely to have tetrahydrocannabinol (THC), the main psychoactive component of marijuana, in their blood compared with age- and sex-matched controls.

Another study determined that motorists killed in wrecks were 2.5 times as likely to have been responsible for the accident when they had THC in their blood.

These are meaningless points when you recognize that:

1. Marijuana is the third-most used drug after alcohol and tobacco, so it is not surprising you’d find it in car crash victims;
2. Marijuana is detectable in the blood long after most other drugs, including alcohol, are not; and
3. Recent studies show that people can test positive for THC in the blood up to a week after ceasing their use of cannabis.

Few somatic effects of chronic use have been documented, Hall and Degenhardt found, except for several case-control studies suggesting promotion of lung cancer. Also, THC increases heart rate in a dose-dependent way, perhaps increasing risks for people with preexisting cardiovascular disease.

Yet when we look at populations of chronic cannabis users, we don’t find any link to lung cancer or heart attacks. In fact, we’re finding that cannabis may be a key to preventing and curing cancer!

Cognitive effects while high are, of course, well recognized, but their persistence is less clear, Hall and Degenhardt said. Some studies say cognitive impairment remains in chronic heavy users even after they quit, but others indicate that recovery of function is the rule.

I’d say we just find some old dudes who’ve smoked pot for fifty or more years and put them in a Jeopardy tournament with old dudes who’ve been drinking for fifty or more years and let’s settle this once and for all!

Similar uncertainty clouds the research on whether marijuana fosters use of other, arguably more dangerous, drugs such as cocaine and heroin, the researchers said. People who use marijuana are more likely to use other illicit drugs as well, but causality has been difficult to prove.

How about “impossible to prove”? The Institute of Medicine in 1999 and every other study since has concluded that there is no “gateway effect”. The only gateway in marijuana is to the dealer of illegal drugs. You know why they don’t call tequila a gateway drug? Because you can’t buy cocaine, heroin, or meth on the shelf next to it.

Marijuana use has also been linked to increased risk of psychiatric disorders including schizophrenia and, less consistently, depression.

Except that, worldwide and nationally, the rates of schizophrenia and psychosis remain virtually static even as cannabis use and potency rises and falls. A recent ten-year analysis of data from the UK found no increase in schizophrenia and psychosis even as rates of cannabis use exploded.

Overall, they concluded that marijuana is clearly associated with negative health and psychosocial consequences, but these are not as major as for some other drugs, and the causal relations remain unproven.

“The focus of epidemiological and clinical research should be on clarifying the causative role of cannabis for these adverse health effects,” the authors said.

Really? You looked and looked and found that lots of people use cannabis and you couldn’t prove that it did much harm to them, so the the focus going forward should be to prove that cannabis did harm them? How about accepting that as drugs go, cannabis is probably the safest one out there, the most beneficial to the most people and the least harmful to society?

They also cited a recent study estimating that marijuana accounted for about 0.2% of the total disease burden in Australia, a nation with one of the world’s highest rates of cannabis use. Its health impact was one-tenth that of alcohol and one-fortieth that of tobacco, the study found.

That makes for a nice sound bite: Cannabis – ten times less damaging to society than alcohol, forty times less damaging to society than tobacco, and yet still illegal.