Drug Arrests in the US, 2010, by Age and Gender
"State and local law enforcement agencies made an estimated 1,336,500 arrests for drug possession or use in 2010. Females were 20% of these arrests. The median age in drug possession or use arrests was 26. Eleven percent of drug possession or use arrests in 2010 involved a juvenile, 18% involved persons age 40 or older, and 6% involved persons age 50 or older."
Snyder, Howard N., "Arrests in the United States, 1990-2010" (Washington, DC: US Dept. of Justice Bureau of Justice Statistics, Oct. 2012), NCJ239423, p. 12.