Researchers at the Salk Institute for Biological Studies have found in a study of mice that repeated emotional stress, the kind humans experience in everyday life, may contribute to the accumulation of neurofibrillary tangles in the animal, which is a hallmark of Alzheimer’s disease.

The researchers say that while aging is still the greatest risk factor for Alzheimer’s disease, a number of studies have pointed to stress as a contributing factor.

“A long-term study of about 800 members of religious orders had found that the people who were most prone to stress were twice as likely to develop Alzheimer’s disease, but the nature of the link between the two has been elusive,” says lead researcher Dr. Paul E. Sawchenko, a professor in the Neuronal Structure and Function Laboratory.

The study, published in the Journal of Neuroscience, suggests that the brain-damaging effects of negative emotions are relayed through the two known corticotropin-releasing factor receptors, namely CRFR1 and CRFR2, which are part of a central switchboard that mediates the body’s responses to stress and stress-related disorders.

In Alzheimer's disease, as well as various other neurodegenerative conditions, phosphate groups are attached to tau protein, as a result of which the protein looses its grip on the microtubules, and starts to collapse into insoluble protein fibers, which ultimately cause cell death.

Previous studies had shown that extreme physiological stress, such as plunging mice into ice water or starving them for three days, can induce tau phosphorylation.