Can Repetitive Negative Thinking Speed Up Cognitive Decline?
Persistently engaging in negative thought patterns may increase dementia risk.
In a 2015 paper, "Cognitive Debt and Alzheimer's Disease," Natalie Marchant and Robert Howard, who is a professor of Old Age Psychiatry at University College London (UCL), proposed a novel concept called the "cognitive debt hypothesis," which posits that repetitive negative thinking (RNT) might be linked to an increased risk of Alzheimer's disease.
Recently, a follow-up study led by Marchant investigated the association between RNT and various markers of Alzheimer's (the most common form of dementia) in a cohort of 292 people over age 55. The findings (Marchant et al., 2020) were published on June 7 in the journal Alzheimer's & Dementia.
Natalie Marchant is the principal investigator and senior research fellow at University College London's Department of Mental Health of Older People within UCL's Division of Psychiatry.
For her latest (2020) study, Marchant and colleagues used three different measures to gauge dementia risk: Subjective cognitive decline, global amyloid levels throughout the brain, and tau deposition in the entorhinal cortex. All of the study participants also completed self-reported RNT, anxiety, and depression questionnaires. About a third (n = 113) of the total cohort (N = 292) had amyloid‐positron emission tomography (PET) and tau‐PET scans.
To measure cognitive performance during this two-year study, the UCL researchers used the Repeatable Battery for Assessment of Neuropsychological Status (RBANS), which consists of 12 different cognitive tests that provide five domain‐specific index scores: Attention, delayed memory, immediate memory, language, and spatial cognition.
For two years, all study participants regularly self-reported their typical thinking process as they went about their day-to-day lives. The "repetitive negative thinking" questionnaires were designed to identify chronic patterns of excessive rumination about past events or worrying about the future in ways that involved catastrophizing.
The researchers found that RNT is correlated with faster cognitive decline and increased amyloid and tau deposition in older adults. Based on this empirical evidence, the researchers speculate that repetitive negative thinking is one of many modifiable psychological factors that may be a marker for increased risk of Alzheimer's disease.
"We propose that repetitive negative thinking may be a new risk factor for dementia as it could contribute to dementia in a unique way," Marchant said in a June 8 news release.
What's the difference between having a positive explanatory style and repetitive negative thinking? Simply put, someone with a positive explanatory style tends to look on the bright side and finds creative ways to reframe adverse life experiences through a more optimistic (i.e., "glass half-full") lens. Conversely, someone who is prone to repetitive negative thinking has trouble identifying silver linings, tends to see the proverbial glass as perpetually half-empty, and is more inclined to be a pessimist. (See "How Learning to 'Expect Nothing' Reshaped My Pessimistic Mindset")
"Taken alongside other studies, which link depression and anxiety with dementia risk (Gimson et al., 2018), 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," Natalie Marchant said in the news release.
She added, "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."
Why Would Repetitive Negative Thinking (RNT) Increase Someone's Risk of Dementia?
The researchers speculate that RNT may increase dementia risk via neural and endocrine pathways associated with chronic stress. Previous Alzheimer's research (Dong & Csernansky, 2009) identified a link between higher levels of stress hormones such as cortisol and increased amounts of amyloid and tau deposition.
Another review (Justice, 2018) on the relationship between Alzheimer's disease and what Nicholas Justice of the University of Texas's McGovern Medical School calls "The Vicious Cycle of Stress" concluded: "Growing evidence indicates that physical and psychosocial stressors, in part acting through the hypothalamic-pituitary-adrenal (HPA) axis, may accelerate the process of Alzheimer's disease."
Natalie Marchant hopes that her team's latest findings on RNT and Alzheimer's disease will lead to the development of specific strategies designed to help people lower their risk of dementia by teaching them how to reduce repetitive negative thinking patterns.
Marchant and colleagues are currently working on a large project to see if RNT-related prevention strategies and interventions such as mindfulness meditation may help reduce dementia risk while supporting overall mental health as people age.
"During these unstable times, we are hearing from people every day on our Alzheimer's Society Dementia Connect line who are feeling scared, confused, or struggling with their mental health," Fiona Carragher, who is the Chief Policy and Research Officer at the Alzheimer's Society UK, said in a June 2020 news release posted during the COVID-19 pandemic. Understandably, the ongoing coronavirus crisis has increased RNT for many people around the globe.
In light of the universal stress created by COVID, Carragher concludes: "So it's important to point out that this study [Marchant et al., 2020] isn't saying a short-term period of negative thinking will cause Alzheimer's disease. Mental health could be a vital cog in the prevention and treatment of dementia; more research will tell us to what extent."
Christopher Bergland is a world-class endurance athlete, coach, author, and political activist.