Is there a loss of efficacy of lithium in patients treated for over 20 years?

Diminishing efficacy of lithium prophylaxis in initially well-responding patients during long-term treatment as well as after interruption of prophylaxis has been described repeatedly in the past. For the present analysis, 22 patients with bipolar and unipolar affective disorder continuously treated and documented in a specialized lithium outpatient clinic over at least 20 years were included. The cumulative affective morbidity of the first 10 years versus the second 10 years of prophylactic treatment was subjected to statistical and single-case (life chart method) analysis. There was no statistical evidence for diminishing efficacy of lithium prophylaxis. The increase in the Morbidity Index in single patients in a case-related individual approach could be revealed as not necessarily due to an alleged loss of efficacy of lithium, but more likely to be due to the atypical features in the psychopathology and course of illness.