Long-term use of pharmacological doses has been associated with adverse effects including renal impairment, hypothyroidism, and tremor (Malhi et al., 2013); However, emerging evidence, including the recent Harvard Nature study (2025) suggests that lithium at physiological or trace levels is necessary for maintaining neuronal integrity, and that deficiency itself may be pathogenic, accelerating amyloid and tau pathology as well as cognitive decline. The gene discussed is MAPT; the disease is Tremor.