Are you a pessimist by nature, a “glass half empty” sort of person? That’s not good for your brain.
A new study found that repetitive negative thinking in later life was linked to cognitive decline and greater deposits of two harmful proteins responsible for Alzheimer’s disease.
“We propose that repetitive negative thinking may be a new risk factor for dementia,” said lead author Dr. Natalie Marchant, a psychologist and senior research fellow in the department of mental health at University College London, in a statement.
Negative thinking behaviors such as rumination about the past and worry about the future were measured in over 350 people over the age of 55 over a two-year period. About a third of the participants also underwent a PET (positron emission tomography) brain scan to measure deposits of tau and beta amyloid, two proteins which cause Alzheimer’s disease, the most common type of dementia.
The scans showed that people who spent more time thinking negatively had more tau and beta amyloid buildup, worse memory and greater cognitive decline over a four-year period compared to people who were not pessimists.
The study also tested for levels of anxiety and depression and found greater cognitive decline in depressed and anxious people, which echos prior research.
But deposits of tau and amyloid did not increase in the already depressed and anxious people, leading researchers to suspect repeated negative thinking may be the main reason why depression and anxiety contribute to Alzheimer’s disease.
“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.
“This is the first study showing a biological relationship between repetitive negative thinking and Alzheimer’s pathology, and gives physicians a more precise way to assess risk and offer more personally-tailored interventions,” said neurologist Dr. Richard Isaacson, founder of the Alzheimer’s Prevention Clinic at NYork-Presbyterian and Weill Cornell Medical Center, who was not involved in the study.
“Many people at risk are unaware about the specific negative impact of worry and rumination directly on the brain,” said Isaacson, who is also a trustee of the McKnight Brain Research Foundation, which funds research to better understand and alleviate age-related cognitive decline.
“This study is important and will change the way I care for my patients at risk.”
More study needed
It is “important to point out that this isn’t saying a short-term period of negative thinking will cause Alzheimer’s disease,” said Fiona Carragher, who is chief policy and research officer at the Alzheimer’s Society in London. “We need further investigation to understand this better.”
“Most of the people in the study were already identified as being at higher risk of Alzheimer’s disease, so we would need to see if these results are echoed within the general population,” she said, “and if repeated negative thinking increases the risk of Alzheimer’s disease itself.”
The researchers suggest that mental training practices such as meditation might help promoting positive thinking while reducing negative thoughts, and they plan future studies to test their hypothesis.
“Our thoughts can have a biological impact on our physical health, which might be positive or negative, said coauthor Dr. Gael Chételat of Inserm/ Université de Caen-Normandie.
“Looking after your mental health is important, and it should be a major public health priority, as it’s not only important for people’s health and well-being in the short term, but it could also impact your eventual risk of dementia,” Chételat said.
Looking on the bright side
Previous research supports their hypothesis. People who look at life from a positive perspective have a much better shot at avoiding death from any type of cardiovascular risk than pessimistic people, according to a 2019 study. In fact, the more positive the person, the greater the protection from heart attacks, stroke and any cause of death.