Laughter is good medicine. Having a chuckle or a full-blown howl that has tears streaming down your face and leaves you gasping for air has a direct improvement in your mood. Even some of the most depressing and dire moments can be lightened with a bit of a chortle. It shouldn’t be a surprise, then, that our moods have an impact on our mental and even physical health. Just as a good temperament can help us feel lighter and better about ourselves and the world around us, negativity can bring us down, increase depression, and even lead to dementia and Alzheimer’s disease.
From Negativity to Dementia and Alzheimer’s
Cognitive decline, especially dementia and Alzheimer’s, is a growing concern among older populations. Numerous studies throughout the years have linked negative thinking with depression, anxiety, and other issues, and now these diseases are on the list as well. “Psychological problems such as depression and anxiety increase the risk of cognitive impairment in older adults,” as found in a BMC Psychiatry study published in 2025. Repetitive negative thinking (RNT) not only puts you and those around you in a bad mood, but it can also increase health risks.
The BMC study, which involved 424 participants aged 60 and older, showed “a negative association between RNT and cognitive function in community-dwelling older adults.” This conclusion isn’t necessarily final, however, as the publication pointed out that multi-center studies and those spanning longer periods are still needed to verify the relationship between RNT and cognitive decline and to “further explore the mechanisms involved.”
The Alzheimer’s Association conducted a study of more than 350 people over the age of 55 as well, and researchers found “'repetitive negative thinking’ (RNT) is linked to subsequent cognitive decline as well as the deposition of harmful brain proteins linked to Alzheimer’s.”
Nearly a third of the participants underwent a PET, or positron emission tomography, brain scan to measure deposits of two known proteins that cause Alzheimer’s: tau and beta amyloid. The results showed that those who spent more time with negative thinking had more buildup of the proteins, and worse memory and cognitive decline over a four-year period than those in the study who generally had more positive thoughts. Furthermore, the levels of depression and anxiety were higher, and there was greater cognitive decline in depressed or anxious participants.
Curiously, those who were depressed or anxious already did not have an increase in tau and amyloid deposits. This led researchers to suspect that negative thinking may be one of the main reasons depression and anxiety lead to dementia and Alzheimer’s disease.
Dr. Natalie Marchant, a psychologist and senior research fellow in the department of mental health at University College London and an author of the study, said in a statement: “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.” She continued:
“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. 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.”
Stay Positive
A sunny outlook has been linked to a healthier retirement, but staying positive can be easier said than done. When one is already depressed or suffers from anxiety disorders, changing the behavior might not be as simple as thinking good thoughts - and depending on the severity, some doctors might recommend antidepressants.
Dr. Helen Kales, a professor and chair of the psychiatry department at the University of California, Davis, told Healthline the results of the study aren’t surprising. “Conversely, those who ‘age well’ without cognitive problems seem better able to think positively, ignore negative inputs, and focus on the positive,” she said.
However, not all hope is lost. Some researchers have been looking into thought training and relaxing processes, such as meditating and mindful thinking. Training the brain to relax and look at the positive might help stave off some negative thinking.
