Has the portion of U.S. adults who use marijuana increased or decreased over the past three years?
Over the past 3 years, the portion of U.S. adults who use marijuana has nearly doubled from 7% to 13%. The average potency of marijuana has increased from about 4% THC in the 1980s to 20% today. THC is the psychoactive ingredient in marijuana, and higher levels of it may increase rates of addiction. Modern pot also has low levels of cannabidiol, a compound thought to have medical uses.