Study finds cannabis least dangerous of illicit recreational drugs


A pair of researchers affiliated with several institutions in Germany, has found that of a number of drugs used by people for recreational purposes (i.e. for non-medicinal reasons and without a prescription) cannabis is the least dangerous—at least when measuring the lethality of a single dose. In their paper published in Scientific Reports, Dirk Lachenmeier and Jürgen Rehm describe their study of the lethality of several illicit drugs and their results.

In most circles, cannabis, aka marijuana, weed, etc., is considered far less harmful to the body than other drugs such as cocaine, heroin or even alcohol—at least in direct short term ways. In this new study, the researchers set out to learn if that is indeed the case. They subjected test animals to high doses of several drugs to learn their lethality levels, then compared what they found with the average use levels of real people who use the drugs recreationally—this allowed them to derive a ratio number they call a Margin of Exposure (MOE)—a measurement tool that indicates the lethality of a drug based on how much of it is usually taken. It does not take much cocaine, for example, to kill a person, but most people take far less than that limit and thus survive to try it again, and again, if they so desire. To show where cannabis stands with other popular recreational drugs, the researchers created a chart showing the MOE of various drugs, which showed that cannabis sat at the very bottom, by far the safest of the bunch, which included from most deadly to least: alcohol, heroin, cocaine, tobacco, ecstasy and meth.

It is doubtful that anyone will be surprised that cannabis is at the bottom of the list, much more surprising is that alcohol is at the top, more deadly than any of the other recreational drugs—a statistic the researchers note that is ironic when considering that selling, buying and consuming alcohol is legal whereas doing the same with is not in most places.

Of course, the research does not take into account the other impacts of the drugs on the list, such as deaths related to drug crimes, car crashes or suicide (or even side effects such lung disease or stroke) or the harm that can be caused by job loss, inattention to child care, or the toll they can take on relationships.

Explore further

Cannabis link to other drugs

More information: Sci Rep. 2015 Jan 30;5:8126. DOI: 10.1038/srep08126.
Journal information: Scientific Reports

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Feb 27, 2015
Good to see this proven, again. Also, NHTSA just released a very comprehensive study that said vehicle crash risk with THC in blood (not just metabolites) is not statistically significant above that of sober drivers.

"Over all, drivers who tested positive for active THC were 25 percent more likely to be involved in crashes. But once the researchers took sex, age, and race/ethnicity into account, the risk ratio shrank from 1.25 to 1.05 and was no longer statistically significant... In other words, the analysis, which NHTSA described as 'the most precisely controlled study of its kind yet conducted,' provides no evidence that marijuana use increases crash risk. That result, the authors note, is similar to what the best-designed previous studies have found: a small or nonexistent increase in crash risk."

It reaffirmed alcohol risk: 4X for .08 and 12X for .15.


Feb 27, 2015
Don't misunderstand the study though (nor my comment), the NHTSA still says you shouldn't drive while "impaired" by THC, but level of impairment, by their own admission, can be dependent on a lot of factors, not just blood concentration of THC (this isn't nearly as true with alcohol).

I'm not saying it's a 'green' light to get high and drive, not at all... Just bringing up this study because it confirms anecdotal evidence by users that it isn't NEARLY as bad as opponents to legalization want you to believe, and it is no doubt significantly less impairing than alcohol...

That means something very important; reading between the lines, if people ditch alcohol for MJ, then that could drastically reduce nationwide crashes, specifically fatal or serious injury crashes...

Feb 27, 2015

Good stuf, thanks for sharing. The only further point i'd add is that if such tests also took frequency and experience into account - of both cannabis usage and driving - the results would show a significant lowering of risk for experienced drivers who are also regular cannabis smokers.

The reason for the small (if valid) statistical risk increase is undoubtedly due to the novelty factors, both of driving and also of the effects of the drug. For more experienced subjects though (in both respects) any such source of distraction is reduced accordingly, and on the contrary, they're likely to be more focused, with greater situational awareness, emotional detachment and loss of excitability..

I don't smoke the stuff and i'm not condoning or recommending that anyone else should. But the widespread misconception that driving stoned is as bad (or worse) than drink-driving deserves more scrutiny, not least where law enforcement is involved..

Feb 27, 2015
How does cannabis compare to licit recreational drugs?

Feb 28, 2015
You don't have to worry about the health consequences of smoking cannabis, either. The author of this article apparently is not familiar with the famous Tashkin study at UCLA, which found pot smokers' lung cancer rate was actually slightly lower than the rate for people who had never smoked anything at all. Tashkin attributed the surprising result of the large cohort, 10-year study to a hypothesized anti-tumor property intrinsic to cannabis.

Feb 28, 2015
The headline is wrong: the most dangerous drug, alcohol, is not illicit (except in Islamic countries, of course).

Feb 28, 2015

In which case, surely the statistics are being skewed by a greater number younger, inexperienced drivers, smoking the same way young people are given to drink - ie. in excess and with a view to getting 'off their faces', who may well be using other drugs at the same time (including alcohol), and prone to social peer-group factors such as other passengers in the car, other young drivers on the road (ie. boy racers) etc. etc.

In short, the real source of the increased risk is probably the 'thrill seeker' mentality that causes younger people to act impulsively and make poor on-the-spot decisions, within which cannabis use likely plays an almost incidental role. In which case a better remedy would be to increase the age limit at which young people can drive unaccompanied by a responsible adult, while limiting the availability of cannabis to youngsters in the same way as alcohol (ie. taking it off the street via licenced vendors), instead of blanket bans.

Mar 09, 2015
I know dozens of people who have "driven while high" and never been in a wreck. The necessary caveat, aside from saying that it's not safe, is knowing your own tolerance level (at the moment, cause it's likely to change based on usage patterns) and ability to resist distraction while keeping focused on the road.

If you're just slightly buzzed, maybe 40 minutes after consumption, and you are a fairly good driver, you probably have nothing to fear at all. If you're 5 minutes out from smoking, you're just starting to be intoxicated and you don't know where it will peak and it might get ahead of your ability to compensate, this is a far more dangerous time to be attempting to drive.

You might call that common sense, but there's a dozen other factors too. How potent is the particular strain, how much did you have, do you know how much you need to be X amount of intoxicated? Have you tried this variety before? Are you on any other drugs, legal or otherwise, that may exacerbate, etc.

Mar 09, 2015
Just "Having THC in your system" doesn't really mean anything. You could have smoked before bed 8 hours previous, got a good night's sleep, be totally sober, and still have active THC in your blood. Especially considering you can detect it in a Urine test as long as 2-3 weeks after consumption, if you were a heavy user before stopping.

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