An observational cohort study with linkage to registers of all prescribed lithium & recorded suicides in Denmark during the period 1995-1999 was conducted. A total of 13,186 patients who purchased at least 1 presciption of lithium & 1.2 million subjects from the general population were included in the study. Patients who purchased lithium had a higher rate of suicide than persons who did not purchase lithium. Purchasing lithium twice was associated with 0.44 reduced rate of suicide compared with the rate when purchasing lithium only once. The rate of suicide decreased with the number of lithium prescritions. (47 refs.)