Thesis (Master's)--University of Washington, 2013It is undisputed in the literature that lithium is essential to human health, but a lithium deficiency syndrome has yet to be defined. Lithium deficiency has been associated with learning disorders, violent crime, impulse controls disorders, Prader-Willi syndrome, and depressed mood in humans. Physiologically, the high ionic potential of lithium causes antagonism with other minerals, e.g. displacement of magnesium, competition with calcium. Lithium is a central nervous system (CNS) depressant at higher doses, although the mechanisms and dose ranges have yet to be elucidated. A substantial body of literature supports the role of lithium in neuroprotection, neurorepair, and neurogenesis throughout the lifespan. Given the purported roles of lithium in the function of the CNS, it was hypothesized that lithium deficiency would be unusually prevalent in patients with neurological disorders. This thesis reviews the roles of lithium in the CNS, reports the frequency of lithium deficiency in patients with Parkinson's disease, and summarizes the state of evidence that lithium is an essential element for neurological health