By Scott Douglas Jacobsen
How did the New Brunswick mystery brain illness investigation and the JAMA Neurology study conclude that no new disease was identified?
The reported mystery brain illness from New Brunswick has been investigated further since 2021’s initial epidemiological research.
In 2021, a group of 48 patients showed neurological symptoms, with the province’s initial investigation finding no common illness. The report was issued on February 24, 2022. A neurologist raised concerns in early 2023 about the possible exposure to herbicides and metals, while additional patients showed abnormal symptomatology.
A 2023-2026 investigation following the initial investigation tested the environmental-exposure hypothesis. They checked if patients received diagnoses since the original research.
The New Brunswick “mystery brain illness” investigation began in 2021 with a group of 48 patients showing neurological symptoms. The province’s first investigation found no evidence of a common illness, and that report was issued on February 24, 2022.
On January 23, 2026, New Brunswick released the report in conclusion of the investigation. By February 28, 2025, 222 complete and validated patient reports had been received. By November 1, 2025, the referring neurologist had notified the province of 399 patients.
Only the 222 validated reports were included in the analysis. No environmental substances explained all or even most patient conditions. Over 90% of patients were within expected ranges for herbicides. Some patients had elevated metal levels. Most were normal.
Provincial reportage, in other words, reports no widespread environmental exposure as contributive to illness. Autopsies revealed known conditions, rather than a “mystery illness” or a new unknown brain disease, including Alzheimer’s, Creutzfeldt-Jakob disease, and Lewy body disease.
More distinctly in the academic domain from a highly reputable medical journal, JAMA Neurology, published a peer-reviewed study on May 7, 2025, with a re-examination of 25 patients from the broader 222-patient cohort. The study included 14 independent clinical evaluations and 11 neuropathological diagnoses.
The JAMA Neurology study found no evidence of a new disease and identified known conditions in the 25 cases, including common neurodegenerative diseases, functional neurological disorder, metastatic cancer, and traumatic brain injury.
11 autopsy cases were found to be extremely unlikely to have a new disease (probability of less than 0.001). The Public Health Agency of Canada (PHAC) helped with two rounds of scientific review. New Brunswick requested a separate review of all data.
No common illness was identified in the first investigation; the second provincial investigation found no new or unknown brain diseases, and the JAMA Neurology study found no evidence of a new disease.
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a close up of a human brain on a white background, image by BUDDHI Kumar SHRESTHA, via Unsplash