Marijuana abuse and dependency are becoming less common, even as states roll back restrictions on the use of the drug, according to a new federal report.
In 2014, the number of Americans age 12 and older meeting diagnostic criteria for marijuana abuse or dependency stood at 1.6 percent, a decline from 1.8 percent in 2002, according to the report released Thursday by the Substance Abuse and Mental Health Services Administration and the Centers for Disease Control and Prevention.
Declines in marijuana abuse and dependency were greatest among teens (37 percent decrease) and young adults (18 percent decrease) over that period. The change in marijuana abuse and dependency among adults age 26 and older was not statistically meaningful, according to the CDC.
These figures come from nearly 900,000 responses to the National Survey on Drug Use and Health, an annual federal survey of American substance use. Dependence and abuse were measured by common criteria set by the Diagnostic and Statistical Manual of Mental Disorders used by the American Psychiatric Association.
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Respondents were considered dependent on marijuana if they reported “health and emotional problems associated with (marijuana) use, unsuccessful attempts to reduce use, tolerance, withdrawal, reducing other activities to use (marijuana), spending a lot of time engaging in activities related to (marijuana) use, or using (marijuana) in greater quantities or for a longer time than intended,” according to the CDC.
Similarly, respondents were considered abusers of marijuana if they reported “problems at work, home and school; problems with family or friends; physical danger; and trouble with the law because of (marijuana) use.”
The study noted that abuse and dependency were relatively rare among marijuana users: only 11.9 percent of people who used marijuana in the past year met one of these criteria. That number’s fallen by nearly 30 percent since 2002, when 16.7 percent of past-year marijuana users were abusers of the drug or dependent on it.
Marijuana dependence and abuse are becoming less common even as more people use marijuana, the CDC found. Past-month marijuana use is up 35 percent since 2002 among Americans age 12 and older, increasing from 6.2 percent that year to 8.4 percent in 2014. Rates of use increased among every age group except for teenagers, who saw a non-significant decrease in use over the same period.
These numbers contradict a report last year from a team of researchers at Columbia University and elsewhere, who found that marijuana use disorders increased between 2002 and 2013. Those figures came from a different national survey which showed a more dramatic rise in overall marijuana use. The authors of the Columbia study said the reason for the differences in use rates between the two surveys is not clear.
Heavy marijuana use — daily or near-daily in any given month — did increase sharply over this period, according to the CDC. About 2 percent of Americans used marijuana daily in the past month in 2002, but 3.5 percent used daily in 2014. Again, though, teens bucked this trend: Daily or near-daily use among 12- to 17-year-olds fell from 2.4 percent in 2002 to 1.6 percent in 2014.
Normally, researchers expect increases in heavy marijuana use to lead to more marijuana abuse or dependency. But the opposite seems to be happening — abuse and dependency are falling as heavy use becomes more common. That represents a public health puzzle.
The CDC authors posit that changes to medical marijuana law might explain some of the discrepancy. “With changes in medical marijuana laws and, in particular, state laws or policies allowing limited access to low percentages of delta-9-tetrahydrocannabinol (THC) or cannabidiol (CBD), persons who use marijuana daily for medical reasons might be using strains that pose lower risk for dependence or abuse,” they write.