A commonly prescribed antidepressant may slow the progression of Alzheimer's disease, according to a recent study.

Researchers from the Washington University School of Medicine in St. Louis and the University of Pennsylvania found that antidepressants, such as citalopram, stopped the growth of plaques in a mouse model of the brain degenerative disease. And in young adults who were cognitively healthy, a single dose of the antidepressant lowered the production of amyloid beta, the primary ingredient in plaques, by 37 percent.

Amyloid beta is a protein produced by normal brain activity. Levels of this protein rise in the brains of patients with Alzheimer's, causing it to clump together into plaques. Plaques also are sometimes present in cognitively normal brains.

"Antidepressants appear to be significantly reducing amyloid beta production, and that's exciting," John Cirrito, senior author of the study and assistant professor of neurology at Washington University, said in a statement. "But while antidepressants generally are well tolerated, they have risks and side effects. Until we can more definitively prove that these drugs help slow or stop Alzheimer's in humans, the risks aren't worth it. There is still much more work to do."

For the study, the team gave citalopram to older mice with brain-plaques. They used a technique called two-photon imaging to track the growth of Alzheimer's-like plaque in the mice for 28 days.  Giving the mice the antidepressant stopped the growth of existing plaques and reduced the formation of new plaques by 78 percent.

In a second experiment, , the scientists gave a single dose of citalopram to 23 people ages 18 to 50 who were not cognitively impaired or depressed. Samples of spinal fluid taken from the participants over the next 24 hours showed a 37 percent drop in amyloid beta production.

The findings were recently published in Science Translational Medicine.