The company is conducting a large-scale trial of the software by collecting hundreds of routine phone conversations between nurses and patients, with consent from both parties. After performing follow-up questionnaires to see which patients are depressed, the researchers tested the software, to see if it could accurately identify these patients. "The trials are still running, but the results are very encouraging," says Feast, who adds that the first results will be published in 2010.

Mark Clements, a professor of electrical and computer engineering at the Georgia Institute of Technology, has analyzed vocal patterns associated with clinical depression. His lab also uses vocal cues to identify deception and anger, as well as early signs of intoxication. Clements says the benefit of Cogito Health's approach is that it could help untrained professionals detect signs of depression. "A trained listener could detect these types of things in a person's voice, but it's difficult to teach a novice," he says. "But things that are hard to hear can be detected by a computer, and have correlations with various emotional and even physical states."

Carl Marci, director of Social Neuroscience at the Massachusetts General Hospital's Department of Psychiatry, and another a scientific advisor to the company, says such technology could help monitor a patient's long-term progress. "As a psychiatrist, I see patients at most once a week, sometimes once a month," says Marci. "They're living their lives in between, and if I had access to a data stream that captured their natural conversations, I could monitor their response to a treatment."

Cogito Health also plans to develop software to detect other mood disorders in at-risk populations. Next year, Feast says, the company will explore vocal patterns associated with post-traumatic stress in soldiers. "We want to enable early detection of psychological distress," says Feast, "because it has been shown that early intervention makes an enormous difference in these post-trauma situations."