In addition to the many adverse health effects that result directly from alcohol misuse, co-morbid conditions often present further complications for individuals with alcohol abuse problems. Alcohol abuse and dependence commonly occur in individuals who suffer from mood, anxiety, and personality disorders as well as the effects of other drugs of abuse. For example, an estimated 90% of cocaine addicts have alcohol problems. It also has been estimated that as many as 60% of patients presenting at community mental health centers have co-morbid alcohol and other drug abuse disorders. Patients suffering from both disorders often have poorer treatment outcomes and are more likely to drop out of treatment. Unfortunately, effective pharmacological and behavioral treatments have yet to be established for the various conditions of co-morbid alcohol and other drug abuse disorders.

The high co-morbidity between alcohol and tobacco dependence poses special problems. Fifty to ninety percent of alcoholics smoke, a rate that is three times higher than among the population as a whole. Alcoholics smoke heavily, are more addicted to nicotine and are less successful at quitting smoking, which puts them at a greater risk for the synergistic effects of alcohol and nicotine on the development of certain cancers and cardiovascular diseases.