The 25-Year Evolution of Lithium as a Disease-Modifying Agent in Dementia

Importance: Lithium, a long-established cornerstone therapy for bipolar disorder, is a biologically plausible disease-modifying agent for neurodegenerative disorders, including mild cognitive impairment (MCI) and Alzheimer disease (AD). Observations: Rather than targeting a single pathology like amyloid or tau, lithium acts across multiple cellular resilience pathways. Chronic lithium exposure induces the anti-apoptotic protein B-cell lymphoma 2 (Bcl-2), enhances brain-derived neurotrophic factor (BDNF) signaling, inhibits glycogen synthase kinase-3β (GSK-3β), stabilizes mitochondrial function, and reduces oxidative stress. These convergent mechanisms promote neuronal survival and synaptic integrity. In humans, proton magnetic resonance spectroscopy studies found that lithium increased N-acetylaspartate levels, consistent with improved neuronal viability, and structural magnetic resonance imaging (MRI) studies found that lithium preserved gray matter and/or reversed illness-related atrophy in hippocampal and corticolimbic regions. In addition, extensive evidence demonstrates that low-dose lithium (approximately 0.3mM)-significantly lower than traditional psychiatric doses (0.6-1.0mM)-exerts robust neurotrophic and neuroprotective effects. Preclinical models have found that these concentrations stimulate hippocampal neurogenesis, promote structural plasticity, and protect against proteotoxic injury. Furthermore, epidemiological studies have associated cumulative lithium exposure with reduced dementia risk, and early randomized clinical trials in MCI suggest cognitive stabilization and favorable tau biomarker changes at low, well-tolerated doses. The recent repletion hypothesis suggests that lithium may also function as a physiological trace element, but these findings await independent replication. Conclusions and Relevance: These convergent data support a prospective clinical trial of low-dose lithium orotate to slow disease progression in MCI. Such an approach would prioritize established neuroprotective mechanisms while potentially mitigating the kidney and thyroid risks associated with higher-dose carbonate formulations. If low-dose lithium can indeed meaningfully alter disease trajectory, it would represent a much-needed, accessible, and inexpensive treatment that may be especially relevant in low- and middle-income countries.