A committee reviewed 53 studies of pharmaceuticals and 37 studies of psychotherapies used in PTSD treatment, and concluded that because of shortcomings in many of the studies there is not enough reliable evidence to draw conclusions about the effectiveness of most treatments.

The report from the Institute of Medicine did say there was sufficient data to conclude that exposure therapies -- such as exposing individuals to a real or surrogate threat in a safe environment to help overcome fears -- are effective in treating people with PTSD.

Nonetheless, the committee emphasized its findings should not be misread to suggest that any PTSD treatment ought to be discontinued, or that only exposure therapies should be used to treat PTSD.

"At this time, we can make no judgment about the effectiveness of most psychotherapies or about any medications in helping patients with PTSD," committee chair Alfred O. Berg of the University of Washington in Seattle said in a statement. "These therapies may or may not be effective -- we just don't know in the absence of good data."