To consider the coexistence of substance use disorders and anxiety disorders, it is particularly important to define the reliability and validity of the anxiety disorder diagnoses in the presence of high levels of substance use. Because most structured psychiatric diagnostic instruments provided little guidance in distinguishing “substance-induced” from “independent” psychiatric disorders, Hasin et al. () added structured probes to a standard diagnostic instrument to improve the reliability of diagnostic decision. When Hasin’s modifications were applied in a clinical substance abuse setting, reliability was improved for several psychiatric disorders. However, the test-retest reliability for anxiety disorders still remained in the low to acceptable range, which was lower than the ranges for major depression and bipolar I disorder. Kranzler et al. () attempted to measure the concurrent and predictive validity of anxiety disorders in a clinical substance abuse setting with a “longitudinal, expert, all data” procedure but found no support for the concurrent validity and only marginal support for the predictive validity of anxiety disorders. Dividing anxiety disorders into those that occurred first and those that occurred after the onset of substance use disorders did not improve the indices of validity (1995). Response to treatment also may be used as a validating criterion for a diagnostic category. At present, no studies of treatment outcome for any comorbid anxiety disorder were designed to address the issue of the validity of the diagnoses of comorbid anxiety disorders in the presence of a lifetime or current history of substance use disorder.
Epidemiological surveys of psychiatric and addictive disorders indicate high levels of comorbidity of anxiety disorders and substance use disorders () as well as high levels of familial aggregation of these disorders (1997). The Epidemiological Catchment Area study indicated that several types of anxiety disorders occurred more frequently in individuals with lifetime alcohol dependence than in the general population (). However, the prevalence ratios for this excess prevalence were modest, the highest being for panic disorder. All of the comorbid anxiety disorder prevalence ratios were lower than those ratios for antisocial personality disorder, mania, and schizophrenia.
In their seminal review of the comorbidity of alcoholism and anxiety disorders, Schuckit and Hesselbrock () concluded that the prevalence of anxiety disorders among persons with alcoholism was equal to or only slightly higher than that in the general population. Although less studied, this appears to be the case for persons who abuse drugs as well (1991). In contrast, Merikangas and Avenevoli (), in their review of clinic- and community-based epidemiological studies of social phobia, concluded that alcohol and drug dependence was overrepresented in patients with social phobia and vice versa. Kendler et al. () showed excess levels of comorbidity between phobic disorders and alcoholism among female twins from a population-based registry. The discrepancy between the review of Schuckit and Hesselbrock () and those of Merikangas and Avenevoli () and Kendler et al. () could be a result of the degree to which females were included in the epidemiological studies.
The effect of gender on the comorbidity of anxiety and substance use disorders was noted in the Epidemiological Catchment Area study (Anthony and Helzer 1991). Women with alcoholism were more likely than men to have another diagnosis. This may be because of the higher prevalence of many of the anxiety and depressive disorders among women () or the greater deviance of alcoholism when it occurs in women, implying that other psychiatric disorders be present to increase the likelihood that a woman would be given a diagnosis of alcohol dependence. Adding a further level of complexity, Magura et al. () recently described distinct patterns of multiple comorbid psychiatric disorders in men and women addicted to heroin.
There are many important gaps in our knowledge about comorbid anxiety disorders and substance use disorders. The most glaring is the absence of systematic information about the effect of multiple psychiatric diagnoses (multiple anxiety diagnoses or anxiety diagnoses with other types of disorders) on substance use (1992). We also do not have information on how various sociodemographic risk factors affect the prevalence or natural history of comorbid anxiety and substance use disorders. These variables have significant effects on the prevalence of substance use disorders (), panic disorder, and phobic disorders () and even on the likelihood of exposure to trauma (1995). How these variables operate on comorbid anxiety and substance use disorders also requires further study.