A study of more than 1 million veterans with psychiatric disorders who received care from the Department of Veterans Affairs (VA) showed that 21 percent were also diagnosed with a substance use disorder.

The research was conducted by Ismene Petrakis, M.D., Robert Rosenheck, M.D., and Rani Desai, Ph.D., who reported their findings in the May-June American Journal on Addictions. All three are associated with the Department of Psychiatry at Yale University and the VA Connecticut Healthcare System.

The researchers undertook the study because of concerns that veterans of the current wars in Iraq and Afghanistan, especially those diagnosed with posttraumatic stress disorder (PTSD), might also have significant problems with substance abuse.

The results could provide direction for the VA as it contemplates the future needs of the current generation of combat veterans.

The study covered all patients treated in VA medical facilities from October 2007 to September 2008. The researchers compared rates of substance use disorders among veterans with PTSD with substance abuse rates among those with other psychiatric disorders: major depression, bipolar disorder, schizophrenia, dysthymia, or an anxiety disorder.

They also compared veterans from different eras: the Vietnam War (1964-1975), the post-Vietnam War era (1975-1991), and the Gulf War/Persian Gulf (1991-present). Veterans who served in Iraq or Afghanistan since 2001 were considered as a subset of the Gulf War–era veterans.

An unexpected finding was the level of comorbidity among patients diagnosed with PTSD. "What was surprising is the relatively low rate of comorbid substance abuse in those with PTSD compared to those with other psychiatric disorders," the researchers wrote.

Patients with PTSD were only marginally more likely to have a substance abuse diagnosis than those without PTSD—21.7 percent compared with 21.1 percent.

In general, veterans diagnosed with bipolar disorder were 1.92 times more likely than those with PTSD to be dually diagnosed, the highest rate of comorbidity. Those with affective disorder had the second highest rate (1.66), followed by anxiety disorders (1.15) and schizophrenia (1.11).

Because of the high absolute numbers of subjects, even these small differences were statistically significant.

When the war eras were factored in, the most likely group to be dually diagnosed was the post-Vietnam cohort. They may have had more exposure to drug use during that time. The researchers suggested that substance use among military personnel declined after 1980.

"That is when routine screening of substance use began," said Wilson Compton, M.D., in an interview with Psychiatric News. "After that, there was a decline in drug use" among U.S. troops. Compton is director of the Division of Epidemiology, Services, and Prevention Research at the National Institute on Drug Abuse.

Current Department of Defense policy takes a hard line against illicit street-drug use.

Among veterans of Iraq or Afghanistan, the strongest comorbidity associations were between substance abuse and bipolar disorder and schizophrenia, but not PTSD.

Despite its large sample, the study's conclusions shouldn't be extrapolated to all veterans, said Compton. The VA's medical system serves as a safety net and thus may reflect a population that is generally in worse health than other veterans or the general public, he noted. "However, this kind of information may be extremely useful in helping the VA plan for services."

For instance, noted Petrakis and colleagues in their report, veterans of the current wars "should likely be screened for serious mental illness in addition to screening for PTSD."

And although dual diagnosis among patients with PTSD was relatively lower than for other condition, the number of combat veterans returning with that condition will mean that the VA will need significant resources to care for those with comorbid substance abuse.

Another planning consideration may arise from the choice of therapies available, said Compton.

The traditional way to treat dual-diagnosis patients was to treat the conditions sequentially, he said. Current recommendations are to treat them simultaneously, which would require different allocations of time and resources.