Harvard Medical School researchers identified brain lithium deficiency as an early and pivotal factor in Alzheimer’s disease onset and progression. Through mouse models and human tissue studies, lithium loss was shown to lead to hallmark Alzheimer’s pathologies including amyloid deposition and tau aggregation, impairing cognition. Importantly, treatment with an amyloid-evading lithium compound reversed these neurodegenerative changes and restored memory function in mice. This discovery redefines lithium’s neuroprotective role and signals potential for lithium-based diagnostics and therapeutics targeting Alzheimer’s disease.