Summary: A recent study reports that selective serotonin reuptake inhibitors (SSRIs), a widely prescribed class of antidepressants, are associated with reductions in biological markers linked to Alzheimer’s disease. In an analysis of 191 individuals from a large neuroimaging cohort, patients with Alzheimer’s disease who were taking SSRIs had lower plasma levels of phosphorylated tau‑181 (p‑tau181), a blood biomarker tied to tau pathology and disease progression.
Brain imaging in the same study also showed that SSRI use was associated with restored metabolic activity in the dorsal raphe nucleus (DRN), a small brainstem region that both produces serotonin and is among the earliest areas to accumulate tau in Alzheimer’s. This metabolic recovery was observed in patients with Alzheimer’s disease but not in healthy control participants, indicating a disease‑specific effect rather than a general increase in serotonergic activity.
Key findings:
- Lower tau biomarker levels: People with Alzheimer’s disease who were on SSRIs had significantly lower plasma p‑tau181 compared with those not taking these medications.
- Restored dorsal raphe metabolism: FDG‑PET scans showed reversal of DRN hypometabolism in AD patients using SSRIs, consistent with recovered glucose metabolism in this vulnerable region.
- Variable cognitive outcomes: Cognitive test results were mixed—some measures showed improvement while others did not—suggesting complexity in how SSRIs influence cognition and how decline is measured.
The dorsal raphe nucleus plays a central role in serotonin signaling and is recognized as an early site of tau accumulation in Alzheimer’s disease. Because SSRIs act on serotonin reuptake, investigators asked whether long‑term SSRI exposure might influence both the biochemical hallmarks of AD and regional brain metabolism.
Researchers analyzed data from 191 participants in the Alzheimer’s Disease Neuroimaging Initiative (ADNI). All subjects had baseline 18F‑FDG PET scans to evaluate glucose metabolism and plasma biomarker measurements for phosphorylated tau‑181. The team compared participants who reported long‑term SSRI use with those who were not taking SSRIs, and evaluated relationships between SSRI status, plasma p‑tau181, regional brain metabolism (with a focus on the DRN), and a range of cognitive tests.
The main biological signal was consistent: Alzheimer’s patients on SSRIs showed reduced plasma p‑tau181 relative to AD patients not on these medications. In parallel, FDG‑PET revealed that the DRN, which typically appears hypometabolic in AD, demonstrated restored metabolic activity in SSRI‑treated patients. Healthy control participants did not show the same DRN metabolic changes with SSRI use, a difference the authors suggest may reflect homeostatic regulation of serotonin signaling in non‑diseased brains.
When cognitive performance was examined, results were heterogeneous. Certain assessments—such as the Montreal Cognitive Assessment (MoCA)—showed better performance for some SSRI users, while other cognitive measures did not indicate clear benefit. The study also observed that usual correlations between different cognitive tests broke down among SSRI users, raising the possibility that antidepressant treatment may alter how cognitive decline is detected rather than uniformly changing its trajectory.
The investigators stress important limitations: this was a cross‑sectional analysis, so causality cannot be inferred. The dataset did not allow precise accounting for specific SSRI types, dosages, duration of treatment, or the timing of SSRI initiation relative to the onset of Alzheimer’s symptoms. These constraints mean it remains unclear whether SSRIs prevent, delay, or simply modify detectable biomarkers of AD.
Nevertheless, the findings support further prospective and controlled clinical trials to determine whether SSRIs can meaningfully alter disease biology, to define optimal timing and treatment duration, and to clarify any cognitive benefits or harms. The results add to a growing body of research linking the brain’s serotonin system with Alzheimer’s pathology and point to the DRN as a region of interest for therapeutic investigation.
About this neuropharmacology and Alzheimer’s disease research news
Author: Neuroscience News Communications
Source: Neuroscience News
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Original research: SSRIs reduce plasma tau and restore dorsal raphe metabolism in Alzheimer’s disease, Dylan J. Terstege et al., Alzheimer’s & Dementia. DOI: 10.1002/alz.14579 (open access).
Abstract
SSRIs reduce plasma tau and restore dorsal raphe metabolism in Alzheimer’s disease
INTRODUCTION
Tau accumulation contributes to neurodegeneration and cognitive decline in Alzheimer’s disease. The dorsal raphe nucleus (DRN) is among the earliest brain regions to display tau pathology and is a major serotonergic center. Selective serotonin reuptake inhibitors (SSRIs) influence DRN activity and have produced mixed effects on cognition and pathology in previous AD studies.
METHODS
The investigators examined 191 participants who had baseline 18F‑FDG PET imaging and plasma biomarker data. They compared measures of DRN metabolism, plasma phosphorylated tau‑181, and cognitive assessments between individuals with and without reported SSRI use.
RESULTS
Plasma p‑tau181 concentrations were lower among SSRI users. The cognitive effects of SSRIs varied depending on the assessment instrument. The DRN showed hypometabolism in Alzheimer’s patients compared with healthy controls, but SSRI use was associated with restored DRN metabolic activity in the AD group.
DISCUSSION
Long‑term SSRI use may be linked to reduced pathological markers of Alzheimer’s disease and to recovery of metabolism in a serotonin‑rich brain region vulnerable to tau. However, the impact on cognitive performance remains variable, and prospective trials are needed to determine causality, optimal timing, and clinical relevance.