Prospective studies on a lithium cohort. 1. General features.

Since 1979, patients started on long-term lithium treatment at the Psychiatric Hospital in Risskov have been followed systematically with recording of clinical and laboratory variables before the start of treatment, after 6 and 12 months of treatment, and thereafter at yearly intervals. By June 1987, 480 examinations had been carried out before the start of lithium treatment, 236 after treatment for 6 months, and decreasing numbers up to 7 years of lithium treatment. The total lithium exposure time was 548 years. The mean lithium dose was 23.2 mmol/d and the mean serum lithium concentration 0.68 mmol/l. These values are about 30% lower than the corresponding values in patients given lithium treatment prior to 1979. About one half of the patients who had gone through the pre-lithium examinations did not reach the 6-month examination. This was because they did not start lithium, or because they stopped it again before 6 months of treatment or before they had reached that point. Thereafter there was a drop-out rate of about 25% per year during the first 2 years of lithium treatment and about 10% per year after 4-5 years of treatment. More men than women left the cohort.