"An admission [to treatment] was considered marijuana-involved if marijuana was reported as a primary, secondary, or tertiary substance. In 1999, 43 percent of all adolescent admissions were marijuana-involved admissions referred to treatment by the criminal justice system, and 39 percent were marijuana involved but referred by other sources. Between 1999 and 2002, the proportion referred by the criminal justice system increased to 45 percent while the proportion referred by other sources decreased to 37 percent. The proportions started to converge in 2007.
"Adolescent admissions not involving marijuana that were referred by the criminal justice system fell from 8 percent in 1999 to 5 percent in 2009. Admissions not involving marijuana that were referred from other sources were fairly stable, at between 9 and 11 percent of adolescent admissions."

Source

Substance Abuse and Mental Health Services Administration, Treatment Episode Data Set (TEDS). 1999 - 2009. National Admissions to Substance Abuse Treatment Services, DASIS Series: S-56, HHS Publication No. (SMA) 11-4646, Rockville, MD; Substance Abuse and Mental Health Services Administration, 2011, p. 29.
http://wwwdasis.samhsa.gov/te…