This article originally appeared in the San Francisco Chronicle on July 9, 2014.
Recreational marijuana has been legal in Colorado for just over six months, and sales figures and national public opinion polls show the idea has caught on. But a study reveals the drug does come with risks, and there are still a lot of health questions that haven’t been answered.
Scientists from the National Institutes of Health published a review of existing marijuana research in the New England Journal of Medicine in June. The findings showed the drug comes with some chance of addiction, and the risk is higher for teens. Driving after using pot increases the odds of being in an accident, but not as much as drinking does. And more research is needed to answer other marijuana health and safety questions, like consequences of secondhand smoke, the impact for pregnant women and babies, and the therapeutic potential of the individual chemicals found in the marijuana plant.
Washington and Colorado have legalized recreational marijuana for those over 21, and Colorado saw more than $200 million in sales in the first four months. California and 17 other states, plus the District of Columbia, have legalized pot for medicinal use, and many are considering legislation that would legalize it more broadly. California’s Proposition 19 failed in 2010, with only 46.5 percent of voters favoring it, but polls show more of the state’s residents support the idea now. However, the issue won’t be on the ballot this year.
Here’s a look at some of the marijuana math:
The percentage of people 12 years and older who reported using marijuana in the past year, the New England Journal of Medicine review found. About 9 percent of people who experiment with marijuana will become addicted, but the percentage rises to about 17 percent of those who start using as teens.
The percentage of high school seniors in the U.S. who said they do not think regular marijuana use is harmful, and 6.5% said they used the drug daily or near daily.
The New England Journal of Medicine report found risk of a car accident doubles when a person drives soon after using marijuana. By comparison, chance of an accident is about five times greater than normal for drivers with blood alcohol levels above 0.08 percent.
The average THC content, or potency, of marijuana samples police confiscated in 2012, according to the journal study. This is up from an average of 3 percent in the 1980s, causing scientists to doubt the current relevance of older marijuana studies.
The percentage of Californians who favor legalization of recreational marijuana use, according to a December 2013 Field Poll. It marked the first time in the poll’s history that a majority of state residents favored making the drug legal.