A team of scientists at Cold Spring Harbor Laboratories on Long Island claims that fluoxetine (Prozac) works by stimulating the proliferation of progenitor nerve cells in a part of the brain called the dentate gyrus. (BBC) Discovering that the medication has this action is a long way, however, from proving that that is how it treats depression. Psychiatric medications cause many brain changes and it is difficult to pinpoint which cause their clinical benefits, which are epiphenomena, and which are consequences of the fact that the patient gets better. The article alludes to a very important fact — for this to be an explanation of how antidepressants cure depression, it would have to be shown to be a mechanism of action common to all medications that have similar antidepressant efficacy. That research remains to be done. The consensus is, however, moving away from a neurotransmitter theory of depression and of how antidepressants work to one based on, essentially, tissue repair, as we appreciate that episodes of depression actually cause physical damage to the brain from, among other things, its exposure to chronically high levels of stress hormones.