A double-blind, placebo-controlled study of the effects of lithium on cognition in healthy subjects: mild and selective effects on learning

Background: Several studies have shown cognitive impairment in short-term m emory, long-term memory and psychomotor speed in bipolar patients taking li thium. The aim of the study was to look at the effect of lithium in normal subjects (N = 30) taking lithium for 3 weeks. A comprehensive battery was u sed to assess attention and memory. Methods: Subjects were randomized to do uble-blind treatment with either lithium (N = 15) or placebo (N = 15) for a 3-week period. Thirteen participants in the lithium group and 15 in the pl acebo group completed the study. The lithium and placebo were administered twice daily in doses varying from 1050 to 1950 mg (mean = 1569 mg). The ini tial daily dose was calculated according to the Pepin formula to achieve a blood serum lithium level of about 0.8 mmol/l. Cognitive performance (atten tion, memory) was assessed in each subjects during three periods, i.e. at b aseline, after 3 weeks of lithium or placebo, and 2 weeks after discontinua tion of study medication. Results: In short-term memory tasks, the performa nce of subjects in the lithium group was worst 3 weeks after lithium treatm ent compared to 2 weeks after discontinuation. In long-term memory, a signi ficantly higher number of words was recalled by the placebo group but not t he lithium group. Conclusions. Lithium may have an effect on learning when long-term explicit memory test are administered repeatedly. It means that t he practice effect when a subject performs the same task several times is l ess in the lithium-treated group than in the placebo group. This practice e ffect is related to the learning of a task. (C) 2000 Elsevier Science B.V. All rights reserved.