Some artificial intelligence researchers now believe that the sound of your voice might be the key to understanding your mental state.

Psychologists have long known that certain mental health issues can be detected by listening not only to what a person says but how they say it, said Maria Espinola, a psychologist and assistant professor at the University of Cincinnati College of Medicine. With depressed patients, Dr. Espinola said, "their speech is generally more monotone, flatter and softer. They also have a reduced pitch range and lower volume. Patients with anxiety feel more tension in their bodies, which can also change the way their voice sounds, she said. "They tend to speak faster.