found a significant association of drug abuse with deployment. The Vietnam Twin Registry study also found an association of deployment with alcohol abuse and with drug abuse. Two of the three studies of Gulf War veterans, one in an Iowa population and one in Australian veterans, found a higher prevalence of alcohol-use disorders in deployed veteran; a third conducted 10 years after the war, did not. The two studies that assessed drug-use disorders in Gulf War veterans both found an increased prevalence of such disorders in deployed veterans. Results from the secondary studies were also mixed: five of the seven studies found a positive association between alcohol abuse or dependence and deployment, but two studies did not. For drug-use disorders, the results were similarly mixed: two studies showed a positive association, but three did not.

Combat exposure has also been associated with an increased likelihood of substance-related problems. The evidence is reasonably consistent for an association with alcohol abuse/dependence but was considered limited but suggestive for drug abuse for two reasons. First, studies of veterans did not adjust for predeployment substance abuse when analyzing postdeployment prevalences. Second, unlike alcohol, drug use is an illegal behavior, and studies of combat soldiers did not screen for drug abuse.

The determinations of drug abuse were based on self-reports, without independent corroboration. Most of the recent studies of Gulf War veterans relied on screening measures or telephone interviews. The studies were cross-sectional, and the findings are based entirely on self-reports. Because substance-use disorders involve externalizing behaviors, corrobation by other sources would have enhanced the validity of information. An important limitation of those studies that might be corrected in the future is the lack of comprehensive, direct assessments of substance disorders that include age-of-onset information.

The committee concludes that there is sufficient evidence of an association between deployment to a war zone and alcohol abuse. The committee also concludes that there is limited but suggestive evidence of an association between deployment to a war zone and drug abuse.

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