DSM-IV defines substance-use disorders as dependence (characterized by tolerance, withdrawal, needing increasing amounts, persistent desire, and unsuccessful efforts to cut down) or abuse (characterized by recurrent use causing domestic, work, interpersonal, or legal problems, or use in physically hazardous situations) of drugs or alcohol. The lifetime and 12-month prevalences of substance-use disorders in the NCS were about 15% and about 4%, respectively (Kessler et al. 2005a,b). Those rates can be 2-3 times higher in men than in women, depending on the substance. The most reliable method for determining a history of substance-use disorders is the diagnostic interview. In treated populations, current drug use is validated with urine screens. In community and military populations in general, current alcohol problems are often assessed with a screening questionnaire. Two well-validated screening tools that were used in several military studies are the CAGE—a four-item scale to assess cutting down [C], feeling annoyed by people criticizing your drinking [A], feeling guilty about drinking [G], and using alcohol as an eye-opener in the morning [E])—and the Alcohol Use Disorders Identification Test (AUDIT)—a 10-item scale developed by the World Health Organization.
A primary study for substance-use disorders is defined as one that had a generalizable sample of deployed and nondeployed veterans, an indicator variable for combat stress, and reliable ascertainment of a substance-use disorder or a problem with alcohol or drugs. Secondary studies failed to fulfill all of those criteria or focused on other populations of interest, such as peacekeepers. Primary studies of substance-use disorders are summarized in Table 6-4.
The committee identified six primary studies on the relationship of deployment stress to substance-use disorders: three of veterans of the Vietnam War and three of veterans of the 1991 Gulf War. The two studies with the richest sources of evidence were the VES conducted by CDC (1988a) and the congressionally mandated NVVRS (Jordan et al. 1991). Designs characteristics of those studies were provided in the preceding section on psychiatric disorders; information specifically related to substance-use disorders is discussed below.
The VES involved a cohort of 2490 Vietnam-theater veterans and a comparison group of 1972 Vietnam-era veterans, who participated in a face-to-face structured diagnostic interview, the DIS, to assess substance-use disorders in 1985-1986. After adjustment for the six baseline characteristics of age at entry into the Army, race, score on an enlistment general technical test, enlistment status (drafted or volunteer), year of entry into the Army, and primary military occupational specialty (tactical or nontactical), CDC (1988a) found that the current (1-month) prevalence of alcohol disorders was significantly higher in the theater veterans (13.7%) than in the era controls (9.2%) (OR 1.5, 95% CI 1.2-1.8). The rates of drug disorders were not significantly different between the groups (0.4% for theater veterans and 0.5% for era veterans; OR 0.9, 95% CI 0.4-2.0). Analysis of the 1-year prevalence data from the VES, however, did not find significant differences in rates of alcohol or drug-use disorders between the theater veterans (14% and 4%, respectively) and the era veterans (16% and 4%, respectively) (Boscarino 1995). There was no significant relationship between severity of combat exposure and either alcohol or drug-use disorders.