Biologists have already found intracellular pathways and genes important in mediating relief from depression. Two researchers, Jessica Malberg and Richard Duman, both of Princeton University, have shown that chronic treatment with Zoloft causes new neurons to be born in the hippocampus, a region important for memory formation.

This discovery is fascinating because it implies that depression may be caused by decreases in neuronal birth. Several brain-imaging studies have shown that the hippocampal areas of depressed patients were actually smaller than those in normal patients. Initially, scientists believed that the
cause of shrinkage was loss of old neurons, but only recently have scientists begun to realize that neurons are continually being born (albeit in minute amounts) in the adult brain. Less than a decade ago, it was believed that only developing fetuses and babies could grow new brain cells. The discovery that neurons were, indeed, being born in discrete regions in the adult brain was
a major revolution in neuroscience. And since we now know that depression is hindering the birth of new neurons,we can look for ways to develop antidepressants that stimulate new neurons.

In fact, Fred (“Rusty”) Gage, of the Salk Insitute, along with members of his lab, has found many kinds of activities, such as exercise or doing puzzles, seem to enhance the growth of new neurons. Gage was one of the first scientists who recognized that adults had self-renewing brain cells. Although exercise has long been touted as a mood booster by those who regularily work out, Gage’s work was one of the first to prove that exercise actually helps the brain grow and adapt to stress. Dozens of studies published since Gage’s early findings indicate that there are different ways to make neurons grow. These findings may eventually lead to other effective ways to combat depression.