Professor proposes theory of depression

Depression, an illness that affects about 10 million Americans a year, may be caused by a lack of nerve cell generation in the brain, according to Princeton neuroscientist Barry Jacobs.

This novel theory, which Jacobs proposed in papers this year, is described in the Oct. 13 issue of Science . It builds on his own research and that of his Princeton colleague Elizabeth Gould, who has shown that the adult brain continuously generates fresh supplies of neurons.

Jacobs' theory proposes that not only does the brain generate new neurons, but this constant influx is critical in maintaining psychological well-being. In short, he suggests that a decreased flow of new neurons plays an important role in precipitating depression and that an increased flow helps bring about recovery.

This process, says Jacobs, occurs primarily in a brain region called the hippocampus, which is involved with learning and memory, but probably in other brain areas as well. If proven in humans, the theory could open new avenues for treating depression.

"This (theory) brings together two very interesting and important lines of work in neuroscience," said Bruce McEwen, a neuroscientist at Rockefeller University.

Jacobs, a professor of psychology, is an expert on serotonin, a brain chemical closely tied to depression. Antidepressant drugs work by boosting or mimicking the activity of serotonin. It is not clear, however, what serotonin does to counteract depression.

Gould, also a professor of psychology, has focused her research on the birth of new neurons -- a process called neurogenesis. In a series of landmark papers, she showed that neurogenesis is a life-long process, refuting the long-held belief the adult brain never gains neurons and only loses them.

In what Jacobs describes as "a remarkable example of cross-fertilization among colleagues," he and Gould began to see possible links between their research agendas, and wondered whether serotonin promotes neurogenesis. They conducted tests in rats and showed that it does.

In one experiment, Jacobs and collaborators administered the antidepressant drug Prozac to rats for three weeks and found a 70 percent increase in neurogenesis in the hippocampus.

"As soon as we showed that serotonin was important in neurogenesis, it occurred to me that neurogenesis might be important in recovery from depression," he said.

Contact: Justin Harmon (609) 258-3601