Medications used to treat post-traumatic stress disorder were used less frequently in the last decade among veterans, a new study shows.

At issue are benzodiazepines, a class of anti-anxiety drugs that include Xanax, Valium, and Klonopin. Long-term use of these medications can lead to addiction.

“One of our concerns is that it’s very, very difficult to get patients off benzodiazepines,” said study coauthor Dr. Matthew Friedman, executive director of the National Center for PTSD and professor of psychiatry at Dartmouth.

Researchers found 37 percent fewer PTSD patients in the U.S. Veterans Affairs health care system were given benzodiazepines between 1999 and 2009. Long-term use (over 90 days) dropped during the same time period by about 65 percent. The findings were published in the Journal of Clinical Psychiatry.

The Departments of Defense and Veterans Affairs now recommend using psychotherapy and/or antidepressants to treat PTSD symptoms in veterans.