Neuropsychiatric researchers at Rush University Medical Center have discovered that depression is a risk factor for developing dementia.

Previous studies have shown a potential link between depression and dementia, but how the relationship works has never actually been determined.

According to the Centers for Disease Control and Prevention (CDC), a reported one in 10 adults in the U.S. suffers from some level of depression.

Lead study investigator Robert S. Wilson, PhD, neuropsychiatrist at the Rush Alzheimer’s Disease Center, sought to determine the precise relationship between the two diseases, and if one ailment increases the risk of developing the other.

The study included 1,764 individuals from the Religious Orders Study and the Rush Memory and Aging Project whose average age was 77 years. None of them reported any cognitive issues at the start of the study. Each year, the participants were analyzed for any evidence of depression, and were tested on various cognitive levels for eight years.

Over the course of the study, 52 percent of the participants developed some form of cognitive impairment, which is typically a precursor to Alzheimer’s disease. The researchers found that those with demetia were much more likely to have a higher level of symptoms related to depression before the onset of their dementia.

“These findings are exciting because they suggest depression truly is a risk factor for dementia, and if we can target and prevent or treat depression and causes of stress we may have the potential to help people maintain their thinking and memory abilities into old age,” Wilson said in a statement.

The findings of the study are published in Neurology, the medical journal of the American Academy of Neurology.