The N.Y.U. study looked at 129 male military veterans all around 32 years old who had significant exposure to combat, screening out any who also had other disorders that might complicate the study, such as depression or alcohol abuse. Researchers conducted a traditional structured interview, known as a Clinician-Administered PTSD Scale, or CAPS, to identify 52 veterans with PTSD and 77 without.
Researchers recorded each interview, then fed the audio recordings through the speech analysis software at SRI International in Menlo Park, Calif. For five years a team of scientists there has been developing speech software that can understand not only what people say, but also what emotions are expressed in how they say it. The team deconstructed the interviews into 40,526 objective speech-based features that documented tone, variation, pacing and annunciation. This same process is used to help automated customer service programs respond to irate customers.
The data was sent back to New York, where Eugene Laska, a statistician in the psychiatry department at N.Y.U., fed it through an artificial intelligence program that searched repeatedly through the thousands of features until it learned which ones best distinguished the patients with PTSD. In the end it settled on just 18.
Patients with PTSD tended to speak in flatter speech, with less articulation of the tongue and lips and a more monotonous tone, the researchers reported. “We’ve known for a long time that you can tell how someone is doing from their voice. You don’t have to be a doctor to know when someone is feeling down,” Laska said. “But this could take some of the fuzziness out of the process, and help clinicians make better decisions.”
Rather than replace traditional diagnostic interviews, he said, potential biomarkers would most likely become a tool to help psychologists make difficult calls. The results of the study are encouraging, and can be built on to create more sophisticated screening tools, said Rachael Yehuda, director of the Traumatic Stress Studies Division at the Mount Sinai School of Medicine, but she cautioned that in its current form, the algorithm may be of limited practical use.
Many patients with PTSD arrive at the psychologist’s office with a host of other disorders, including depression and substance abuse, and it is unclear how well speech analysis would fare under more complicated real-life circumstances, Yehuda said. Also unclear is whether the signals identified by the algorithm are caused by PTSD or pre-existing conditions that make patients more vulnerable to the disorder, she said.
“We should be enthusiastic but sober,” she added. “This is an important effort. But mental health conditions are complicated and I suspect there is more work to be done.”
Marmar agreed that the technology will need more work before it can be deployed to the field, but said his team hoped to eventually apply for approval by the Food and Drug Administration. “The advantage of this approach is it’s noninvasive and it will become low cost, and easy to perform,” he said. “In theory, we could use this assessment on troops anywhere in the world.”