After combat duty in Iraq or Afghanistan, members of the National Guard appear to have higher rates of mental health problems than those in the Active Component, researchers have found.
Rates of post-traumatic stress disorder (PTSD) with serious functional impairment increased from about 7 percent to more than 12 percent over a nine-month period, compared with only about a 1 percent increase among those in the Active Component, according to Jeffrey Thomas of Walter Reed Army Institute in Silver Spring, Md. and colleagues.
The researchers reported their findings in the June issue of Archives of General Psychiatry.
"The emergence of differences ... likely does not have to do with the differences in the health effects of combat, but rather with other variables related to readjustment to civilian life or access to health care," they wrote.
Longitudinal studies have shown that the incidence of PTSD is two to three times higher among those exposed to combat than those not exposed. But these studies have shown varying prevalences of PTSD and depression and have not assessed other accompanying problems, including functional impairment, alcohol misuse and aggressive behaviors.
So the researchers assessed 18,305 soldiers from four Active Component and two National Guard infantry brigade combat teams, all of whom had combat exposure.
The soldiers completed mental health surveys between 2004 and 2007, at three and 12 months following their deployment.
Overall, the researchers found that rates of PTSD and depression ranged from 9 percent to 31 percent, depending on the level of functional impairment reported.
Generally, National Guard soldiers had significant increases in depression and PTSD symptoms between the three- and 12-month time points, while depression symptoms remained stable for Active Component soldiers. This group also had increases in PTSD symptoms, but not as great as those among the National Guard members.
"Symptoms of PTSD increased significantly in both groups but with much larger increases observed in National Guard participants," the researchers wrote.
For instance, the DSM-IV-diagnosed rates of PTSD with serious functional impairment in the Active Component was 7.7 percent at three months and 8.9 percent after a year. For the National Guard, those numbers were 6.7 percent and 12.4 percent, respectively.
Using the least stringent definition of PTSD, those rates ranged from 20.7 percent among the Active Component at three months to 30.5 percent among the National Guard component after a year.
The difference likely has to do with readjustment to civilian life or access to health care, since National Guard soldiers return to civilian status following their deployment. Thus, they don't have the same uninterrupted access to military medical care as Active Component soldiers, the researchers wrote.
Regarding depression, the researchers found that prevalence rates -- based on the Patient Health Questionnaire (PHQ) -- ranged from 11.5 percent among National Guard members at three months to 16 percent among Active Component soldiers at that same time point.