People who chronically worried or ruminated on negative thoughts had higher rates of cognitive decline and a greater likelihood of harmful proteins in their brains than those who didn’t.
Persistent worrying — which cognitive scientists call repetitive negative thinking — may speed up cognitive decline. It might also make people more susceptible to Alzheimer’s and related dementias.
A 2020 study by researchers at University College London found that repetitive negative thinking (RNT) is linked to cognitive decline and to deposits of amyloid and tau proteins which are key biomarkers of Alzheimer’s disease. The research was published this summer in the journal Alzheimer’s & Dementia.
Lead author Dr. Natalie Marchant at UCL Psychiatry says depression and anxiety in middle and old age are already known to be risk factors for dementia, but the study’s findings get at the root cause:
“We propose that repetitive negative thinking may be a new risk factor for dementia as it could contribute to dementia in a unique way,” Marchant said in a news release. “We found that certain thinking patterns implicated in depression and anxiety could be an underlying reason why people with those disorders are more likely to develop dementia.”
The Link Between Worry, Stress and Alzheimer’s
Previous research has not only found a link between anxiety and depression and the aggregation of harmful proteins in the brain, but that repetitive negative thinking plays a key role. Dr. Richard Isaacson, a neurologist and director of Weill Cornell University’s Alzheimer’s Prevention Clinic told Being Patient in a recent BrainTalk that repetitive negative thinking can “fast forward amyloid and tau deposition, which fast forwards shrinkage of the memory center of the brain.”
According to Dr. Nancy Donovan, a geriatric psychiatrist at Brigham and Women’s Hospital, anxiety may be a bigger culprit in this process than depression.
As Donovan told Being Patient, “When compared to other symptoms of depression such as sadness or loss of interest, anxiety symptoms increased over time in those with higher amyloid beta levels in the brain.”
According to the researchers, while longterm anxiety or short-term stress may lead to RNT, RNT can in turn lead to chronic stress, and the hormones associated with chronic stress may be the root cause of the cognitive changes observed in the study. Marchant said the affect is slow and cumulative.
“Taken alongside other studies, which link depression and anxiety with dementia risk, we expect that chronic negative thinking patterns over a long period of time could increase the risk of dementia,” Marchant said. “We do not think the evidence suggests that short-term setbacks would increase one’s risk of dementia.”
What the Study Found: The Impact of Repetitive Negative Thinking on Cognitive Decline
Over a four-year period, researchers observed 350 people older than 55. For two years, participants responded to questions about how they think about negative experiences, helping researchers detect RNT patterns like dwelling on the negative experiences in the past and worrying about the future.
Participants were also assessed for depression and anxiety symptoms, and for cognitive function, including measuring memory, spatial cognition, attention and language. About one third of the participants underwent PET scans, measuring Alzheimer’s biomarkers tau and amyloid deposits in their brains.
The findings indicated that those who exhibited more RNT also experienced more cognitive decline over four years, more decline in memory, and a greater likelihood of amyloid and tau deposits.
Researchers found that participants’ depression and anxiety were linked to subsequent cognitive decline, but not to amyloid nor tau deposition. This suggested that RNT may be the primary reason depression and anxiety contribute to a heightened risk of Alzheimer’s.
Because RNT is linked to stress and could cause or perpetuate stress, the researchers said it may also drive other stress-related Alzheimer’s risk factors, such as high blood pressure.
Marchant and colleagues said further research is in order to assess RNT as a dementia risk factor, and to determine effective psychological tools that could address RNT. They are presently working on a large-scale research project to better understand whether interventions like meditation and mindfulness could reduce dementia risk by supporting mental health in old age.
“We hope that our findings could be used to develop strategies to lower people’s risk of dementia by helping them to reduce their negative thinking patterns,” she said.