No one can stay positive all the time, but a new study suggests we should try to be less negative.

Researchers at University College London found that persistently engaging in negative thinking might raise your risk of developing Alzheimer's disease.

For the study, researchers at UCL, McGill University and the French National Institute of Health and Medical Research studied 292 people over the age of 55.

For two years, researchers asked study participants how they tend to think about negative experiences, focusing on RNT - repetitive negative thinking - patterns like "rumination about the past and worry about the future." The participants also completed measures of depression and anxiety symptoms.

Not only were memory, attention, language and other cognitive functions assessed, but 113 participants also underwent PET scans. Those scans measured deposits of tau and amyloid, two proteins that cause Alzheimer's when they build up in the brain.

People with higher RNT patterns showed more cognitive decline over a four-year period, researchers found, and they were more likely to have amyloid and tau deposits in their brain.

And even though depression and anxiety have been associated with cognitive decline, they haven't been linked with amyloid or tau deposits, "suggesting that RNT could be the main reason why depression and anxiety contribute to Alzheimer's disease risk."

"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," lead author Natalie Marchant said.

"Taken alongside other studies, which link depression and anxiety with dementia risk," she continued, "we expect that chronic negative thinking patterns over a long period of time could increase the risk of dementia. We do not think the evidence suggests that short-term setbacks would increase one's risk of dementia. 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."

These results are similar to an April study by Orb Media that concluded that people with a positive attitude about getting older live longer and have better mental health. Those who look at aging as a bad thing "are more likely to suffer a heart attack, a stroke or die several years sooner."

Visit The Atlanta Journal-Constitution (Atlanta, Ga.) at www.ajc.com