The meaning of serum lithium levels in maintenance therapy of mood disorders: a review of the literature.

Since Cade first described the role of lithium in the treatment of manic-depressive patients 40 years ago, there has not been consistent agreement on the relationship between the serum level of lithium during maintenance therapy and clinical outcome. This is a comprehensive review of literature reporting on lithium dose-response relationships, with particular emphasis on a consideration of serum levels of lithium. Efficacy studies are systematically discussed as are those that consider the relationship between serum level and adverse effects. Even after 40 years of lithium use, the relationship between serum levels of lithium during maintenance therapy and clinical outcome, including the development of side effects, remains obscure.