According to the Substance Abuse and Mental Health Services Administration (SAMHSA):

An estimated 24.6 million individuals aged 12 or older were current illicit drug users in 2013, including 2.2 million adolescents aged 12 to 17.

Of the estimated 22.7 million individuals aged 12 or older in 2013 who needed treatment for an illicit drug or alcohol use problem, 2.5 million received treatment at a specialty facility