Researchers attribute the initial low number to the euphoria–a honeymoon period–of coming home, and not thinking too much about the war they’d just experienced. Then as time goes on the troubles begin to sink in. As the Army Times reports:

Of particular note: 20 percent of active-Army soldiers sought or were referred for mental health care, as opposed to 40 percent of reservists and National Guard. Are soldiers among the latter more susceptible to having mental health issues? It’s possible. The study also cited reservists moving on in civilian life without a strong military support community, as reasons for the high percentage.

Still, the Army reports some different reasoning for why the reservist numbers are much higher:

The Washington Post highlighted the issue of substance abuse taken up by the JAMA study:

Here’s a recent CBS News interview with a veterans activist taking a look at the state of mental health issues in the military: