What we know we don't know: Prozac and the brain

For twenty years, psychology has harbored the idea that depression is the lack of a certain brain chemical - serotonin. Simply add the right dosage and type, presto - no more depression. This is the Chemical Hypothesis. Except, it doesn't work for everyone. And taking non-depressive folks and blocking their serotonin doesn't make them depressed. In fact, the Chemical Hypothesis of a chemical imbalance is "wrong" or "very incomplete", actually.

So what's going on? A new theory has been formed. Brain death.

New testing reveals that depression is created by neuron death; brain cells shrinking and dying. Prozac, and drugs like it, allow those dying neurons to be healed, thus alleviating depression. An entirely new theory, forcing psychology and pharmacology to create new treatments.

"The best way to think about depression is as a mild neurodegenerative disorder," says Ronald Duman, a professor of psychiatry and pharmacology at Yale. "Your brain cells atrophy, just like in other diseases [such as Alzheimer's and Parkinson's]. The only difference with depression is that it's reversible. The brain can recover."

It does explain a few things, but it creates a hell of a lot of new questions, too. Which at the end of the day is what science is supposed to do.