Persistent negative thoughts could increase dementia risk, scientists say

Having persistent negative thoughts over a long period of time may increase the risk of dementia, new research suggests.

A team of scientists from the University College London (UCL) have found repetitive negative thinking (RNT) is linked to the deposit of harmful proteins in the brain associated with Alzheimer's disease, the most common type of dementia.

The team said these risks are associated with long periods of RNT rather than short-term negative thinking, with lead author Dr Natalie Marchant, of UCL Psychiatry, adding: “We do not think the evidence suggests that short-term setbacks would increase one's risk of dementia.”

In the study, which was supported by the Alzheimer's Society, the researchers looked at 292 people over the age of 55 over a period of two years.

The participants completed questionnaires about how they typically think about negative experiences, and measures of depression and anxiety symptoms were also taken into account.

Cognitive functions were assessed using measures such as memory and attention span, as well as spatial cognition and language, while brain scans were used to measure the deposits of two types of brain proteins, tau and amyloid, associated with Alzheimer's disease.

The data showed that participants with higher RNT patterns experienced more cognitive decline over a four-year period and were more likely to have harmful protein deposits in their brain.

However, depression and anxiety were found to be associated with subsequent cognitive decline but not with either amyloid or tau deposition in the brain.

According to the researchers, their findings suggest RNT could be the main reason why depression and anxiety contribute to Alzheimer's disease risk, with stress indicators such as high blood pressure also playing a role.

“Depression and anxiety in mid-life and old age are already known to be risk factors for dementia,” Dr Marchant explained.

”Here, 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.

“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.”

Based on the findings, which were published in the journal Alzheimer's & Dementia, the scientists are now calling for further research into RNT as a potential risk factor for dementia.

Fiona Carragher, director of policy and influencing at Alzheimer's Society, said that while the link between RNT patterns and both cognitive decline and harmful brain deposits is interesting, further investigation is needed to understand more about this connection.

“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 and if repeated negative thinking increases the risk of Alzheimer's disease itself,” she said.

As part of the next steps, Dr Marchant wants to find out if reducing RNT through mindfulness training or other targeted therapies could help lower the risk of dementia.

The UCL team and other European researchers are currently working on a large project to see if interventions such as meditation may help reduce dementia risk by supporting mental health in old age.