We all worry to some degree about the future—but a new study shows that those who repeatedly think negative thoughts—like ruminating on them constantly—may be more at risk for developing Alzheimer’s disease or dementia in the future.

The study, published in the journal Alzheimer’s and Dementia, followed 360 people over the age of 55 for two years, examining their mental state. In particular, they watched for how likely these people were to engage in what the study refers to as patterns of “repetitive negative thinking,” or RNT. They also monitored the participants’ depression and anxiety levels to see if that made any difference in disease onset.

The result: The study found that indeed, higher levels of RNT were likely linked with cognitive decline across several domains in the brain, including episodic memory and global cognition—two areas that are associated with a person’s likelihood develop Alzheimer’s later on in life.

Additionally, researchers performed brain scans on 113 of the participants to determine the amount of protein plaque buildup in the brain. As predicted, participants who had high levels of RNT also had higher levels of a protein called tau, a predictor of certain forms of dementia. Moreover, participates also had higher levels of another protein called amyloid-beta, also associated with a higher risk for Alzheimer’s.

Don’t worry if you stress over the future sometimes—the researchers want to make it clear that they’re referring to repetitive negative thinking—it’s really the repetition that’s most dangerous here.

“Chronic negative thinking patterns over a long period of time could increase the risk of dementia,” said study author Natalie Marchant. “We do not think the evidence suggests that short-term setbacks would increase one’s risk of dementia.”

While it’s not certain how much RNT may begin to harm cognition, researchers believe it has to do with the higher stress levels that consistent negative thinking can bring.

Additionally, people who think this way may have higher blood pressure and release more cortisol (the stress hormone), both of which have been shown to stimulate the creation of tau and amyloid-beta proteins.

The takeaway of the study? Manage your stress and you might be able to reduce your risk of developing Alzheimer’s or dementia in the future. Some ways to do that include trying to get in some exercise everyday, downloading a meditation app, journaling, and even laughing—all of which have been proven to help bring down stress levels.

How do you manage ruminating on negative thoughts all the time?