A recent study in Denmark explains why. Researchers studied all (20,581) people who received treatment for an illicit substance use disorder in Denmark over a ten-year period (January 1, 1996 to December 31, 2006).
When people entered treatment both their primary and secondary drugs of abuse were recorded. The study found that “a primary cannabis use disorder was associated with a five-fold increase in mortality” compared to the general population of the same age.
The researchers note that this increased mortality might be the result of a higher rate of car crashes among marijuana users, intentional or violent injuries or homicides, and other kinds of accidents or injuries associated with marijuana use. Patients’ secondary use of other drugs could also explain some of the excess mortality among those treated for cannabis use disorder.
The study found higher mortality rates among those treated for every illicit drug disorder except MDMA (cannabis, five-fold increase; cocaine and amphetamines, six-fold increase; heroin, nine-fold increase, and other opiates, eight-fold increase).
Mikkel Arendt, Povl Munk-Jorgenson, Leo Sher, and Signe O.W. Jensen. Mortality among individuals with cannabis, cocaine, amphetamine, MDMA, and opioid use disorders: A nationwide follow-up study of Danish substance users in treatment. Drug and Alcohol Dependence 114 (2011) 134-139.