In 2013, 7% of adults in the U.S. smoked marijuana. By 2016, this figure had grown to 13%, which is an 86% increase since 2013. The average potency of marijuana has risen by about 2-7 times since the 1970s. 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.