Adults dependent on alcohol report high rates of illegal drug use and nonmedical use of prescription drugs, as compared with the general population. Seventy percent of those with alcohol dependence had never received treatment for that problem or other substance abuse.
Source
Hedden, S.L., et al. Patterns of illegal drug use among an adult alcohol dependent population: Results from the National Survey on Drug Use and Health. Drug and Alcohol Dependence 106(2-3):119–125, 2010; and comparison data for the general population aged 18 or older from the 2007 NSDUH. [Full Text (PDF, 532KB)]