Published online on Oct. 30, the study finds that the predictors of suicide among veterans in depression treatment differ from those seen in the general American population, with younger, white, non-Hispanic men having the highest risk among the veterans.
Veterans with substance abuse issues, and those who had been hospitalized for psychiatric reasons in the year before their depression diagnosis, also had a higher suicide risk. Surprisingly, older veterans who had been diagnosed with post-traumatic stress disorder in addition to depression had a lower overall rate of suicide than those without a PTSD diagnosis, perhaps because they were more likely to receive care through Veterans Affairs PTSD programs.
Though the study did not directly compare populations of veterans and non-veterans receiving treatment for depression, the study does confirm that suicide rates were very high among depressed VA patients during the study period of 1999 to 2004, reinforcing the need for the VA's recent initiatives to prevent suicide.
The study, conducted by researchers from the VA Ann Arbor Healthcare System and the University of Michigan Health System and U-M Depression Center, will appear in the December American Journal of Public Health issue focused on veterans' issues.
The researchers analyzed comprehensive data from 807,694 veterans of all ages diagnosed with depression and treated at any Veterans Affairs facility nationwide between 1999 and 2004. The data are from the VA's National Registry for Depression, developed and maintained by the Serious Mental Illness Treatment Research and Evaluation Center at the VA Ann Arbor's Health Services Research and Development Center of Excellence.
In all, the researchers found that 1,683 of the depressed veterans committed suicide during the study period, representing 0.21 percent of the depressed veterans studied. They then analyzed the characteristics of all the depressed veterans who committed suicide, and calculated suicide hazard ratios and suicide rates per 100,000 person-years for each subgroup.
"Doctors learn about patient characteristics that might increase risk of suicide," says first author Kara Zivin, Ph.D., a VA investigator and assistant professor in the U-M Department of Psychiatry. "Typically, these are older age, male gender, and white race, as well as depression, and medical or substance abuse issues. But our study indicates that among veterans in depression treatment, the predictors of suicide may not be the same. We hope our findings will help guide physicians in understanding suicide risk among currently depressed veterans."
Zivin and senior author Marcia Valenstein, M.D., an associate professor of psychiatry at U-M and leader of this study, note that these data are but the first of many findings that will likely emerge from analysis of the VA data.
"We are also examining whether there are specific periods during depression treatment when veterans are at higher risk and might need higher levels of monitoring," says Valenstein. "In addition, we are examining whether different types of depression treatments, such as different antidepressants or sleeping medications, are associated with different rates of suicide."
The study divided veterans into three age groups: 18 to 44 years, 45 to 64 years, and 65 years or older. It did not assess whether they had served in combat during a particular conflict, although the existence of a disability connected to military service was considered.
Interestingly, the depressed veterans who did not have a service-connected disability were more likely to commit suicide than those with a service-connected disability. This may be due to greater access to treatments among service-connected veterans, or more stable incomes due to compensation payments.
For their analysis, the researchers included all veterans who had received at least two diagnoses of depression during the study period, or had received both a diagnosis of depression and filled a prescription for an antidepressant. Veterans with bipolar disorder, schizophrenia or schizoaffective disorders were not included because of their different prognoses compared with people who have "unipolar" depression. In all, the analysis included data from 807,694 of the 1.5 million veterans diagnosed with depression since 1997.
When the researchers calculated suicide rates over the entire 5.5 year study period, they were much higher for men (89.5 per 100,000 person-years) than for women (28.9), and higher for whites (95 per 100,000 PY) than for African Americans (27) and veterans of other races (56.1). Veterans of Hispanic origin had a lower rate (46.28 per 100,000 PY) of suicide than those not of Hispanic origin (86.8). Adjusted hazard ratios also reflected these differences.
Difference in rates among depressed veterans of different age groups were striking, with 18-44-year-olds committing suicide at a rate of 94.98 suicides per 100,000 person years, compared with 77.93 for the middle age group and 90 for the oldest age group.
The initial findings revealed a suicide rate of 68.16 per 100,000 PY for depressed veterans who also had PTSD, compared with a rate of 90.66 for those who did not. This surprising finding led the researchers to dig deeper and look at whether specific subgroups of depressed veterans with PTSD had higher or lower suicide risk. Further examination demonstrated that the "protective" effect of having PTSD in addition to depression was strongest among veterans in the two older age groups.
The authors say their study does not reveal a reason for this "protective" effect, but they theorize that it may be due to the high level of attention to PTSD treatment in the VA system and the greater likelihood that patients with PTSD will receive psychotherapy. More study is necessary, they say.