"In depressed women, particularly those who respond well to an SSRI antidepressant, they have a larger left brain advantage for hearing words than women who are not depressed," Bruder explains. Conversely, "women who respond poorly to a SSRI antidepressant actually have less left brain advantage."
Burder says hearing seems to correspond to depression, though he's not sure exactly how. He does know that brain activity is essential to hearing. What people hear in the right ear most directly activates the left brain. And what's heard in the left ear engages the right brain. "I guess our best guess is that we know that depression is related to biochemical imbalances in the brain," he explains. "One possibility is that those biochemical imbalances affect, differently, the left brain and the right brain and that there's an imbalance between what's happening in the left and right brain and that that imbalance is part of depression."
Nationwide, depression strikes about 19 million Americans each year and one in ten adults reported a depressive episode annually, statistics gathered by the National Institute of Mental Health show. Depression can bring on loss of appetite, decreased ability to think or concentrate, recurrent thoughts of death or suicide, changes in sleep patterns, and feelings of worthlessness, among other symptoms.
Nearly half of all patients being treated for depression don't respond to SSRI medications, which doctors prescribe to patients 80 percent of the time, Stewart says. When such treatment fails to offer relief, patients can get discouraged: "Part of being depressed is to be easily frustrated and so they get frustrated with the treatment and say, 'Treatment doesn't work. I might as well keep bungling along,' whereas if we could give them the treatment that's going to work for them the first time around you're going to have a lot less frustration."
Bruder's test results have been replicated in three separate studies, showing equal accuracy each time: "In the last study we did we found that women who had above normal left brain advantage for hearing words had about a 95% chance of doing well on Prozac. And that compares with the same women having only a 10% response to a placebo."
So, what will happen to patients whose listening test indicates that SSRIs won't work? "Unfortunately, it's not pinned down yet what is for you," Stewart says. "Now we know what's not for you. We know what not to try. We still have a laundry list of other things to try so the odds are still very good for you. I think they're actually improved because we're more likely to give you what's going to work for you than if we gave you the SSRI which is not going to work for you."
Bruder's next step is to try the listening test in a clinical setting such as doctors' offices. Should it prove as accurate there, Bruder's listening test may help patients like Niosi defeat the kind of depression that can crush life's small pleasures.
This research appeared in the September 2004 issue of the journal Neuropsychopharmacology and was funded by the National Institute of Mental Health.