Effect of lithium carbonate on circadian periodicity in humans

Five groups of two volunteers lived during four weeks under arctic summer conditions (Spitsbergen) isolated in huts, without time information. They received lithium carbonate or placebo. All showed free-run of their circadian temperature and activity/rest rhythms with periods longer than 24 hours. Under lithium carbonate, a period-lengthening effect can be shown. This could help to understand theprophylactic effect of lithium salts in manic-depressive episodes.