Comorbidity and dual diagnosis
Comorbidity, or the co-occurrence of two or more mental illnesses, is the rule rather than exception in mental healthcare settings. Further, dual diagnoses, or the co-occurrence of mental illness and substance use disorder, is among the most commonly reported forms of comorbidity in the general population. For example, epidemiologic research indicates that individuals with substance use disorders are significantly more likely to meet criteria for internalizing psychopathology, such as mood (OR=2.8, CI=2.5-3.1) and anxiety (OR=1.9, CI=1.7-2.1) disorders, than those without substance use diagnoses (Grant et al., 2004). Further, Kessler et al. (1997) reported that 56.8 percent of male and 72.4 percent of female respondents to the National Comorbidity Survey (n=8,098) who reported abusing alcohol also met criteria for another DSM-III diagnosis.