Serotonin is a natural brain chemical that is responsible for several functions including mood, sleep and appetite. The chemical’s levels are lower in people with Alzheimer’s or severe cogitive decline such as in dementia. Johns Hopkins researchers looked into the brain scans of persons with only mild loss of thought and memory and found that they, too, have significantly low levels of serotonin in their brains. So does a low level of the chemical cause cognitive decline, or is it the other way around? The researchers’ new study examines people with early stages of memory decline and shows conclusively that the chemical loss is causing the memory loss rather than the other way round. A related report published alongside the study concludes that if ways could be discovered to either stop or slow the loss of serotonin or to inject a substitute chemical into the brain, the progression of Alzheimer’s and other dementias could be stopped.