It is also backed up by work done on both people and laboratory animals, which shows that stress changes the activity of neurotransmitters, the chemicals that carry signals from one nervecell to another in the brain.
The other concept, pursued by Pfizer, Japan's Ono Pharmaceutical, the AstraZeneca-Renovis partnership and numerous other firms, is to find a brain-cell protector that could be used to stabilize nerve cells and prevent further damage.