Narrator: This is Science Today. High levels of a stress hormone commonly thought to be a symptom of depression may actually turn out to be the cause of depression. Dr. Owen Wolkowitz, a professor of psychiatry at the University of California, San Francisco, says at least some cases of depression may actually be a disorder of the endocrine system, which affects the brain rather than the body.
Wolkowitz: What we think is happening is that under conditions of stress, plus genetic susceptibility, the adrenal gland puts out more cortisol, the cortisol feeds back onto the brain and has effects in the brain - maybe in the hippocampus - that then cause depression.
Narrator: The story gets even more interesting when you consider high levels of cortisol may actually lower levels of neurotransmitters such as serotonin. Low levels of serotonin are thought to underlie depression.
Wolkowitz: In fact, the two abnormalities may feedback on each other. If that's the case, we could either attack it biochemically by increasing levels of serotonin with drugs like Prozac or we could attack it by lowering levels of cortisol.
Narrator: For Science Today, I'm Larissa Branin.