HOW TO INTERPRET FINDINGS ON MORTALITY OF LONG-TERM LITHIUM TREATED MANIC-DEPRESSIVE PATIENTS - CRITIQUE OF DIFFERENT METHODOLOGICAL APPROACHES

Many studies have shown that patients with affective disorders have a mortality markedly higher than that of the general population. Studies of manic-depressive patients given prophylactic lithium treatment hav e yielded varying results, Some authors have reported mortalities whic h were more than four times that of the general population, Others hav e found mortalities which did not differ significantly from that of th e general population. In order to examine these discrepancies we re-an alysed the data of a previous study by IGSLI, using three different me thods to calculate the Standardised Mortality Ratio (SMR). The data ba se was enlarged by adding mortality data from two additional centres, The results indicate that the discrepancies may result from the common use of a 'cumulative' approach which produces a distortion of the dat a if the treatment duration is not taken into consideration properly. An analysis which eliminates this artefact and takes the treatment dur ation into account ('year-by-year' approach) provides the strongest ev idence that the mortality of lithium treated patients is not significa ntly different from that of the general population.