SummaryThe most relevant psychological and neuropsychophysiological effects induced by lithium in healthy volunteers or in patients during the free interval are changes of vigilance and possible changes in patients' personality. In EEG terms lithium acts as a “chopper” and induces left-hemispheric asymmetry. Interesting concepts for description of personality changes are the typus melancholicus of Tellenbach and the psychoanalytical view of depression. Effects in an individual patient are heterogeneous and cannot be predicted. Primary and secondary psychological effects may influence compliance, and a detailed analysis of compliance seems necessary.