The effects of lithium carbonate on healthy volunteers: mood stabilization?

A 2-month lithium-placebo double-blind cross-over study was carried out with 17 healthy volunteers. Their mood was self-rated: twice daily (AM, PM) with the Visual Analogue Mood Scale (VAMS); weekly with the analogue scales for subjective states and body symptoms; and three times (basal and at the end of each treatment period) with the Profile of Mood States (POMS). Memory and reaction time were also assessed, but did not show any change. The mean VAMS score decreased during lithium treatment, but the mean mood variability, a measure of the mean successive differences between consecutive mood ratings (delta squared), did not change significantly. There was a tendency toward decreased mood variability on lithium, both during the full 1-month treatment period and in the last week of treatment, when all volunteers had a lithium serum level ranging from 0.6 to 1.0 mEq/liter. The lower mean VAMS scores on lithium could be attributed to lithium-induced dysphoric mood as recorded on the analogue scales and POMS. However, very large inter- and intraindividual differences in response to lithium were observed. Actually, lithium even had an opposite effect on some volunteers' mood. The data and problems involved with assessment of mood and its changes are discussed.