Repetitive Negative Thinking Linked To Higher Alzheimer’s Risk
Repetitive negative thinking, including constant worry and rumination, has been linked to Alzheimer’s-related brain changes. Here’s what researchers found and whether a 90-minute nature walk helps.
If you are someone who constantly replays the bad days in their mind, or are worrying about what would happen next or dwelling on everything that can go wrong, it's time that you start relooking your thought process. That's because this pattern of overthinking over the negatives of life could be doing more harm to you than simply affecting your mood. Research has found that their is a link between this pattern of negative thinking and other biological changes that are associated with Alzheimer’s disease, although scientists also stress that it does not clearly prove that overthinking causes Alzheimer’s.
The research that was published in Alzheimer’s & Dementia in 2020, looked at 292 older adults, including participants who underwent brain scans to measure amyloid and tau. These are two proteins that are strongly associated with Alzheimer’s pathology. Researchers assessed what they called repetitive negative thinking (RNT), which includes two familiar behaviours: worrying about the future and ruminating over negative experiences from the past.
Does Rumination Cause Alzheimer’s?
The researchers found that people with higher levels of repetitive negative thinking showed greater decline in global cognition as well as immediate and delayed memory. Higher RNT was also associated with greater amyloid deposition and entorhinal tau deposition. These associations remained even after researchers adjusted for potential confounding factors, including depression and anxiety.
This is where the findings of the research become all the more interesting. The researchers have proposed the concept of 'Cognitive Debt,' a hypothesis which suggests that repetitive negative thinking could potentially be one pathway through which psychological stress factors are associated with the risk of Alzheimer’s disease. However, this remains a hypothesis for now. The study was also observational, which means that it could identify an association but could not establish that negative thinking or rumination caused the protein build-up or cognitive decline. The researchers specifically called for intervention studies to determine whether reducing RNT could actually alter Alzheimer’s risk.
So, Can A 90-minute Walk Help?
This is where another study has entered the conversation online. A separate 2015 Stanford-led study, published in PNAS, looked at whether spending time in nature could reduce rumination. Researchers randomly assigned 38 healthy adults to either a 90-minute walk through a natural setting or a 90-minute walk in an urban environment. Those who walked in nature reported reduced rumination and also showed reduced activity in the subgenual prefrontal cortex, a brain region associated with rumination.
However, there is an important distinction: the 90-minute nature-walk study did not study Alzheimer’s disease, amyloid or tau. It cannot therefore be used to claim that walking in nature prevents Alzheimer’s or clears Alzheimer’s proteins from the brain.
What the evidence does suggest is that repetitive negative thinking is worth paying attention to as a potentially modifiable behaviour, while activities such as spending time in nature may help reduce rumination in the short term. Whether changing these thought patterns can actually reduce future Alzheimer’s risk is a question researchers are still investigating.
So, the takeaway isn't that every anxious thought is damaging your brain. Rather, persistent patterns of worry and rumination may deserve attention, and finding healthy ways to interrupt that cycle could benefit mental and potentially long-term cognitive health.