"Significant gaps" in the evidence underlying nearly all treatments for posttraumatic stress disorder make it impossible to judge their value, according to a study released in October by the Institute of Medicine (IOM).

Poorly designed and executed studies have failed to include enough veterans or account for important comorbidities like depression, substance abuse, or traumatic brain injury, said the IOM committee that conducted the study.

Only exposure therapies had amassed sufficient evidence of efficacy, said the committee, which grouped prolonged exposure therapy with other approaches like cognitive-behavioral therapy or cognitive-processing therapy that also include some element of exposure to reminders of trauma.

"Treatments may or may not be effective, and 'inadequate evidence' doesn't mean treatments don't work," said committee chair Alfred Berg, M.D., M.P.H., a professor of family medicine at the University of Washington School of Medicine in Seattle, in a telephone news conference accompanying the report's release. "We just don't know because of the [poor] quality of the evidence."

The report's call for better, more relevant research resonated with many in the field.

"There are not a ton of studies, and we should be funding more research," said Patricia Resick, Ph.D., director of the National Center for PTSD's Women's Health Sciences Division at the VA Boston Healthcare System and a professor of psychiatry and psychology at Boston University. Resick is starting to train 600 VA therapists in cognitive-processing therapy, which she developed 20 years ago.

However, the report's high threshold for including and evaluating studies created another dilemma.

"I think the IOM has set the bar too high," Resick told Psychiatric News. "This is the harshest set of critiques I've ever seen, and I would hate to limit our practice based on that."

The IOM committee eliminated many useful studies by applying current standards to trials that were acceptable when they were designed, she said." Trials take years to plan, run, and publish, but treatment must go ahead in the meantime."

Others worried about the effects on patients' and therapists' attitudes toward treatment.

"This study will be valuable if it facilitates research, but not if it decreases access or willingness to treat patients, especially using medications," said Darrel Regier, M.D., M.P.H., director of APA's Division of Research and executive director of the American Psychiatric Institute for Research and Education, in an interview. "I'd hate to see therapeutic nihilism come out of this report. There are not enough people doing exposure-based psychotherapy to cover the need."

The IOM study began with a systematic search of the medical literature, yielding 2,771 studies. Rigorous inclusion standards eliminated nonrandomized, uncontrolled, or observational studies, so that only 90 randomized, controlled trials remained for analysis.

"The committee may have used an overly conservative standard, but that allowed them to make the most defensible statements," said Stevan Hobfoll, Ph.D., a distinguished professor and director of the Applied Psychology Center and the Summa-KSU Center for the Treatment and Study of Traumatic Stress at Kent State University in Ohio. Hobfoll was not on the committee but served as a peer reviewer prior to the report's release.

"Clearly, clinicians will use a looser standard, but the study will inform their judgment," he told Psychiatric News.

A review of 37 clinical trials of pharmacotherapies found" inadequate" evidence to determine the value of antidepressants, benzodiazepines, anticonvulsants, alpha blockers, and second-generation antipsychotics (such as olanzapine or risperidone) for treating PTSD.

The 53 studies of psychotherapies led the committee to conclude that only exposure therapies had proven efficacy. They found the evidence inadequate to determine the utility of eye-movement desensitizing and reprocessing, cognitive restructuring, coping-skills training, and group therapy.

The committee also noted that many drug trials were funded by pharmaceutical companies and that many trials of psychotherapies were conducted by those who had developed them. Both of these patterns raised questions of bias and generalizability, they said.

Taken together, studies of PTSD therapies carried out since the criteria for PTSD were first included in DSM in 1980 "do not form a cohesive body of evidence about what works and what does not work," wrote the committee in its report. Many studies lacked internal validity because of high dropout rates and poor handling of missing data.

"The bottom line is the number of studies is small, and the quality could be improved," said Farris Tuma, Sc.D., chief of the traumatic stress research program at the National Institute of Mental Health, who was not involved in preparing the report. "The report does the scientific community a service and raises the bar for standards of treatment."

The IOM report is the third in a series requested by the Department of Veterans Affairs asking for guidance in diagnosing, treating, and assessing disability in veterans with PTSD. Coverage of the reports on diagnosis and disability standards appeared in the July 21, 2006 and June 1 Psychiatric News issues, respectively. The reports were originally commissioned because of complaints that too many veterans were requesting disability compensation for PTSD.

The current report was not intended to say which therapies did or did not work or to guide clinical choices, but rather to serve as a guide to those designing the next generation of clinical trials.

"Concluding that the evidence is inadequate to determine efficacy is not the same as concluding that a treatment modality is inefficacious," said the authors. They added that they had found no evidence that any treatment was harmful or ineffective.

These conclusions may raise questions for those familiar with existing PTSD treatment guidelines. For instance, the VA's National Center for Posttraumatic Stress Disorder recommends "SSRIs as first-line medications for PTSD pharmacotherapy in men and women with military-related PTSD." APA's practice guideline on acute stress disorder and posttraumatic stress disorder says that SSRIs "represent reasonable clinical interventions...."

However, the IOM committee noted that while there were more clinical trials of SSRIs than of other drugs, outcomes were split in the seven most useful studies. The largest study of SSRIs showed no improvement in primary PTSD outcomes and saw many patients drop out.

APA's Steering Committee on Practice Guidelines is currently reviewing the IOM report.

One member of the IOM panel dissented from the committee's conclusions on medications, preferring to separate civilian from veteran populations and the latter into chronic patients and those with more recent exposure to war.

"The effect of [SSRIs] in civilian and specific veteran subpopulations must be noted as separate conclusions," wrote Thomas Mellman, M.D., a professor of psychiatry at Howard University." [P]redominantly male veteran populations with chronic PTSD are less responsive to treatments in general."

Mellman also disagreed with the group's emphasis on the limitations caused by the last observation carried forward method for handling data from subjects who drop out of studies, an issue that also troubled Resick.

"I think they were overly critical on the dropout question," she said. "Saying that a 20 percent dropout rate for PTSD is too high is too strict, given that avoidance is one of the prime symptoms of the disorder."

The report offered several recommendations in the light of its findings. In the future, researchers should be required to standardize treatment and outcome measures, define recovery, avoid conflict of interest, and find acceptable ways to track subjects who drop out of trials or to account for the dropouts' data. It also called for more research on veterans and suggested that veterans groups might contribute to clinical trial design and execution.

The VA announced in October that it will convene a consensus conference with the Department of Defense and the National Institutes of Health to" improve the designs and methodologies all three agencies will use in future research studies" for PTSD, according to a press release.

Meantime, clinical practice should be informed by the committee's findings, but not exclusively, said Hobfoll. Practitioners should judiciously apply the empirical literature as the evidence warrants, he said.

"The report is not well suited to guide clinical care," added Tuma. "If we rely solely on randomized, controlled trials, it would be very difficult to develop clinical treatment guidelines. Guidelines combine good science and clinical experience."

The IOM's report comes at a crucial time as many U.S. troops return from war with PTSD and comorbidities.

"We need not just more research," said committee member David Matchar, M.D., director and a professor of medicine at the Center for Clinical Health Policy Research at Duke University, at the news conference. "We need more research that will help clinicians in their practice."

"Treatment of PTSD: An Assessment of the Evidence" is posted at<www.iom.edu/CMS/3793/39330/47389.aspx>.▪