Brain Scans Uncover Tau Buildup in Late-Onset Psychosis Patients

A groundbreaking study conducted in Japan has shed new light on the potential biological underpinnings of psychosis that emerges later in life. Researchers discovered a strong association between the onset of psychotic symptoms after the age of 40 and the accumulation of amyloid-beta and tau proteins in the brain. These proteins are well-established biomarkers for Alzheimer's disease and other neurodegenerative conditions. Intriguingly, a substantial portion of the patients displayed tau protein deposits in the absence of amyloid, indicating a complex and varied set of brain changes that may contribute to late-onset psychosis. This research suggests that for some individuals, psychosis developing in middle to older age could be an early manifestation of a broader neurodegenerative process.

Protein Accumulation and Psychosis Onset

Psychotic disorders, characterized by symptoms like hallucinations and delusions, typically manifest during adolescence or early adulthood. However, in a subset of individuals, these symptoms appear for the first time after age 40, sometimes even after 60, a phenomenon referred to as late-onset psychosis. This later-onset form often presents with distinct clinical features compared to earlier-onset psychosis. For instance, older patients frequently experience prominent persecutory delusions but exhibit fewer negative symptoms, such as emotional blunting or social withdrawal, and less disorganized thinking. These observed differences have led to the hypothesis that late-onset psychosis might involve unique brain alterations.

Previous investigations, including small brain imaging studies, have identified changes in white matter, particularly in the posterior regions of the brain, and altered cerebral blood flow in some individuals with late-onset psychosis. A significant Swedish study also indicated a heightened risk of subsequent dementia in those who develop psychosis after age 60. Post-mortem brain analyses of such cases have revealed various neurodegenerative diseases, including disorders characterized by abnormal tau accumulation distinct from Alzheimer's pathology. The Japanese research team's use of florzolotau, a novel radioactive tracer, allowed for the in-vivo detection of diverse tau buildups, advancing the ability to study these pathologies in living patients. This technological advancement facilitated a more comprehensive understanding of the neural changes associated with late-onset psychosis, moving beyond the limitations of autopsy-based studies.

Investigating the Neuropathological Link

Researchers Manabu Kubota and Shin Kurose, along with their colleagues from the National Institutes for Quantum Science and Technology in Japan, utilized the florzolotau tracer to explore the brain changes underlying late-onset psychosis. Their central hypothesis was that amyloid-beta and tau protein accumulation would be more prevalent in individuals with late-onset psychosis compared to healthy older adults. The study involved 37 patients diagnosed with late-onset psychosis and 47 healthy older adults serving as a control group. The patient cohort had an average age of 70, while the healthy participants averaged 66 years old. A majority of the patients were diagnosed with either schizophrenia or delusional disorder, and none exhibited signs of cognitive impairment or neurological disease at the initial onset of their psychotic symptoms.

All participants underwent both magnetic resonance imaging (MRI) and two positron emission tomography (PET) scans. One PET scan was designed to detect amyloid-beta, while the other employed florzolotau to visualize tau. The results were striking: 35% of the patients exhibited amyloid-positivity compared to only 2% of the healthy controls, with all amyloid-positive patients having developed psychosis after age 60. Tau buildup was even more widespread, found in 65% of patients versus 15% of healthy participants. The patients could be categorized into three roughly equal groups: those with both amyloid and tau positivity (consistent with Alzheimer's), those with tau buildup but no amyloid (suggesting other tauopathies), and those with neither. These findings strongly support the notion that late-onset psychosis is often linked to diverse tau-related neurodegenerative processes, potentially representing an early stage of a dementing illness, although long-term follow-up is necessary to confirm this progression.