A 2016 survey of 16,573 young adults by the U.S. Department of Health and Human Services found that 15.1% had an alcohol or drug use disorder. This data is based on a scientific, nationally representative face-to-face survey, and the margin of sampling error for this result is plus or minus 0.6 percentage points with 95% confidence. By substance, 10.7% had an alcohol disorder, 7.0% had an illicit drug disorder, 5.0% had a marijuana disorder, and 1.1% had an opioid disorder. The first link below provides a more detailed breakdown of these results. The second link provides the definition of substance abuse.