Figures from the “Results From The 2014 National Survey On Drug Use And Health: Detailed Tables” report.

Look at Table 5.14A “Substance Dependence for Specific Substances in the Past Year, by Age Group: Numbers in Thousands, 2013 and 2014”

Total for marijuana and hashish (2014): 2,656,000
Total for ages 12-17 (2014): 304,000