In 2013, 7% of adults in the U.S. said they currently smoked marijuana. By 2017, this figure had grown to 12%, which is a 71% increase. Other evidence, such as drug test failure rates, indicates that usage of marijuana and other psychoactive drugs has grown significantly in recent years. 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 and mental health problems.