Among 94 cognitively healthy adults aged 21-89 followed with up to three scans over three years, higher repetitive negative thinking (RNT) predicted faster global cortical amyloid accumulation on Florbetapir-PET (B = 0.0120, 95% CI 0.003 to 0.021, P = 0.012), independent of anxiety and depressive symptoms. The highest versus lowest RNT tertiles differed significantly in amyloid rate, with the steepest rises in the precuneus, posterior cingulate and medial frontal cortex. RNT did not predict glucose metabolism or grey matter changes, and neither anxiety nor depression predicted any imaging outcome.
The specificity is the interesting part: the signal attached to the ruminative thinking style rather than to mood symptoms, which supports the "psychological debt" hypothesis and fits earlier work linking RNT to tau and amyloid burden and to cognitive decline. Rumination also tracks with sleep disruption and chronic stress physiology, two plausible routes to amyloid clearance problems, though nothing here tests mechanism. Caution is warranted: 94 people is small, the wide age range dilutes relevance to midlife and older adults (though sensitivity analyses in those 50 and over held), and an observational design cannot separate cause from early pathology that itself promotes brooding. Amyloid rise also does not guarantee dementia. This is a preprint awaiting peer review, so estimates may shift. Practically, it adds a reason to take rumination seriously and to consider CBT or mindfulness-based approaches, which reduce RNT, but no trial yet shows that doing so slows amyloid. Incremental but provocative, and it needs replication in larger cohorts.