"Patients aged 20 or younger accounted for 18.8 percent (922,953 visits) of all drug-related ED visits in 2010. About one half (45.3 percent, or 417,856 visits) of these visits involved drug misuse or abuse, representing a rate of 476.1 ED visits per 100,000 population aged 20 or younger."

Source

Substance Abuse and Mental Health Services Administration, Center for Behavioral Health Statistics and Quality. "The DAWN Report: Highlights of the 2010 Drug Abuse Warning Network (DAWN) Findings on Drug-Related Emergency Department Visits," (Rockville, MD: July 2, 2012), p. 2.
http://www.samhsa.gov/data/2k…