Long-term outcome of lithium prophylaxis in bipolar disorder: a 5-year prospective study of 402 patients at a lithium clinic.

OBJECTIVE: In this prospective study, information was collected on all bipolar I patients who started lithium prophylaxis at a lithium clinic during more than 15 years.
METHOD: Patients were evaluated bimonthly with standardized instruments for as long as they took lithium. Treatment surveillance conformed to internationally accepted guidelines. Five years after starting prophylaxis, each patient was contacted for a follow-up interview.
RESULTS: Of the 402 enrolled patients, 27.9% were no longer taking lithium at follow-up; 38.1% were taking lithium and had had at least one recurrence of the disorder; and 23.4% were taking lithium and had had no recurrence. Among patients still taking lithium whose plasma lithium levels had been below 0.5 mmol/liter on no more than 10% of checks, 88.0% had at least a 50% reduction in mean annual time spent in the hospital compared to a reference pretreatment period, and 43.0% had had no recurrence. Patients not taking lithium at follow-up had a poorer outcome than those taking lithium, but patients no longer taking any psychotropic drug did not differ from those taking lithium. Patients no longer taking lithium had had a higher frequency of psychotic features in the index episode than those still taking lithium.
CONCLUSIONS: The impact of lithium prophylaxis on the course of bipolar disorder is severely limited by the high dropout rate. In bipolar patients taking lithium regularly for several years, a drastic reduction of time spent in the hospital is almost the rule; these patients represent a self-selected population in which at least one group at high risk of poor outcome is under-represented.