A computer program can analyze the voices of war veterans and determine which of them has post-traumatic stress disorder with 89% accuracy, said a study published in the journal Depression and Anxiety.

The results suggest voice could be a biomarker for PTSD, providing the basis for an objective test to diagnose the disease. The preliminary study was conducted by researchers at New York University School of Medicine and funded in part by the Army.

“This could really change the landscape of PTSD treatment,” said Thea Gallagher, clinic director of the University of Pennsylvania’s Center for the Treatment and Study of Anxiety. She was not involved in the study. “Helping people begins with diagnosis. And it’s hard to know how many people we’re missing right now.”

PTSD affects more than 24 million Americans, national statistics said. Many are veterans or law enforcement members, but the disease also affects people who have experienced assault or abuse, natural disasters, terrorist attacks, or other traumatic events.

PTSD is diagnosed by a clinician interview in which a mental health professional determines whether a patient is experiencing distress because of a triggering event. The accuracy of that diagnosis is largely dependent on how much the patient shares.

But individuals with PTSD often repress traumatic memories and the associated emotions. Many hide their symptoms out of fear or shame, said Charles Marmar, co-author of the study and chair of the psychiatry department at the NYU School of Medicine. “They may be having nightmares three times a week,” Marmar said, “but do they want to tell you that?”

Cultural and racial biases of the clinician or patient can also affect diagnosis. An objective test could remove these barriers, Marmar said.

In the study, researchers recorded standard clinical interviews with 53 male veterans from Iraq and Afghanistan who had PTSD, as well as 78 without the disease. The recordings were fed into a voice software that recognized more than 40,000 speech features, such as tone and frequency of pauses.

An artificial intelligence tool was used to identify 18 speech features that were most useful in determining whether a person had PTSD. These included monotonous speech, slower speech, more pauses, and a lifeless, metallic tone — all features associated with numbing, Marmar said. Numbing, or the blunting of emotions, is often seen in patients with untreated PTSD.

Researchers theorize that traumatic events change brain circuits that process emotion and muscle tone, which in turn affect voice. “People in active panic or fear sound different than when at coffee with a friend,” Gallagher said.

Down the line, researchers hope to develop an app that could take in audio and screen people for PTSD in minutes.

The study authors are also working to develop a blood test that could identify PTSD based on more than two dozen biomarkers found in blood.