Most people associate lithium with psychiatry, the mood stabiliser handed to patients with bipolar disorder, sitting in a medicine cabinet alongside heavy-duty prescriptions. What very few people know is that lithium isn't just a drug. It's a naturally occurring element found in soil, water, food, and the human brain itself. And according to a landmark study published in Nature in August 2025, when the brain starts running low on it, Alzheimer's disease may not be far behind.
That finding, from a team of researchers at Harvard Medical School, has quietly reshaped how scientists are thinking about what actually triggers Alzheimer's. Not as a single-cause disease, but as one where lithium depletion could be a critical, overlooked factor in the chain of events that leads to memory loss.
What the Harvard research found
The study showed for the first time that lithium occurs naturally in the brain, shields it from neurodegeneration, and maintains the normal function of all major brain cell types. The researchers analysed human brain tissue from people at various stages of cognitive health, alongside a series of mouse experiments, and what they found was striking. Lithium levels in the brains of patients with mild cognitive impairment and Alzheimer's disease were significantly lower than those of healthy controls. Amyloid beta plaques, the hallmark lesions of Alzheimer's, were actively binding to lithium, reducing its availability in the surrounding brain tissue. So not only does lithium fall as the disease develops, the disease itself is actively pulling lithium away.
When the researchers deliberately lowered lithium levels in mice to mimic what they'd seen in human tissue, the results were alarming. Reducing cortical lithium by approximately 50 per cent markedly increased the deposition of amyloid beta and the accumulation of phospho-tau, and led to pro-inflammatory microglial activation, the loss of synapses, axons and myelin, and accelerated cognitive decline. In other words, lithium deficiency alone was enough to produce the full picture of Alzheimer's pathology.
The team then tested a novel lithium compound, lithium orotate, designed to evade capture by amyloid plaques. It reversed Alzheimer's disease pathology, prevented brain cell damage, and restored memory in mice at doses roughly one-thousandth of what's used in psychiatric treatments. Senior author Bruce Yankner, professor of genetics and neurology at HMS, said the idea that lithium deficiency could be a cause of Alzheimer's, rather than just an associated feature, represents a genuinely different therapeutic approach.
Prior evidence supporting lithium's role
In Denmark in 2017, researchers found that regions with naturally higher trace levels of lithium in drinking water had lower rates of dementia across the general population. Then in 2022, a large retrospective cohort study from the University of Cambridge, published in PLOS Medicine, looked at nearly 30,000 mental health patients in the UK. Patients prescribed lithium for mood stabilisation were less likely to receive a dementia diagnosis despite carrying a higher baseline risk for the condition. And in 2024, a meta-analysis brought the clinical picture into sharper focus. It found that lithium treatment was linked to a significant decrease in Alzheimer's risk, with a relative risk of 0.59 meaning people on lithium had roughly 41 per cent lower odds of developing the disease. The same analysis found that lithium outperformed high-cost antiamyloid therapies, including aducanumab and lecanemab, in network analyses of cognitive outcomes in people with mild cognitive impairment.
So the story of lithium and Alzheimer's isn't about a wonder mineral or a simple fix. It's about the brain's chemistry being more fragile and more interconnected than we knew.
About the Author: Maitree Baral is a health journalist on a mission: making medical science digestible and healthcare approachable. Covering everything from wellness trends to life-changing medical research, she turns complex health topics into engaging, actionable stories readers can actually use.
