Which substance is most commonly used and abused by adolescents?

In 2013, an estimated 24.6 million Americans aged 12 or older—9.4 percent of the population—had used an illicit drug in the past month. This number is up from 8.3 percent in 2002. The increase mostly reflects a recent rise in use of marijuana, the most commonly used illicit drug. Marijuana use has increased since 2007.