Marijuana Research Review Details Harmful Outcomes of Use

A review of 20 years of marijuana research concludes there are real risks to using the drug, according to researchers. These include increased risk of car crashes, dropping out of high school and cognitive impairment. Marijuana does not produce fatal overdoses, the review notes.

According to the review, published in the journal Addiction, research in the past 20 years has shown that driving while marijuana-impaired approximately doubles the risk of car crashes. About 10 percent of regular marijuana users develop dependence. Regular use of the drug during the teenage years doubles the risks of dropping out of high school and of cognitive impairment in adulthood. “Regular adolescent cannabis users have lower educational attainment than non-using peers but we don’t know whether the link is causal,” the researchers note in a press release.

The review looked at marijuana studies conducted from 1993 to 2013. It found marijuana use in teens is strongly associated with the use of other illegal drugs. It is not known whether marijuana use causes teens to start using other drugs, the review noted.

Lead researcher Wayne Hall of the University of Queensland Center for Youth Substance Abuse Research in Australia concluded marijuana use probably increases cardiovascular disease risk in middle-aged adults, “but its effects on respiratory function and respiratory cancer remain unclear, because most cannabis smokers have smoked or still smoke tobacco.”

Hall noted that the amount of THC, the psychoactive ingredient in marijuana, has increased in the past 20 years. “The impacts of increased potency on cannabis use should be a research priority,” he wrote.

The review listed other adverse effects of regular marijuana use, including a twofold risk of experiencing psychotic symptoms and disorders, especially in someone with a personal or family history of psychotic disorders who starts using marijuana in their mid-teens.