Repetitive negative thinking is linked to cognitive decline and the development of harmful brain deposits seen in early Alzheimer’s disease, a new study has found. Over time, this thinking style may lead to an increased dementia risk, say investigators.

More than 290 participants aged over 55 were questioned about their thinking patterns, including rumination about the past and worry about the future. They were also screened for depression and anxiety symptoms. Those who had higher repetitive negative thinking patterns experienced more decline in memory, attention, spatial cognition, and language over four years. In addition, participants who underwent brain scans were more likely to have the Alzheimer’s markers amyloid and tau in their brain.

While depression and anxiety were also shown to be tied to cognitive decline, investigators did not find a link to amyloid or tau deposition. This finding suggested that repetitive negative thinking could be the main reason why depression and anxiety contribute to Alzheimer’s disease risk, the researchers claim.

“We propose that repetitive negative thinking may be a new risk factor for dementia as it could contribute to dementia in a unique way,” said Natalie Marchant, Ph.D., from University College London. “Depression and anxiety in mid-life and old age are already known to be risk factors for dementia. 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.”

The researchers do not believe that short-term setbacks would increase one’s risk of dementia.

The study was published in the journal Alzheimer’s & Dementia.