Does lithium exert an independent antisuicidal effect?

Aim of study: Recent investigations have indicated that adequate lithium tr eatment lowers the suicide mortality associated with affective illness. One important question is whether the mechanism by which lithium prophylaxis m ay be effective in prolonging survival can be explained exclusively in term s of successful protection against the recurrence of depressive episodes, o r whether one should consider an independent anti-suicidal factor. Methods: We investigated a group of high-risk patients with recurrent affective dis orders (n = 167) who had committed one or more suicide attempts before the start of lithium prophylaxis within a collaborative project by the Internat ional Group for the Study of Lithium Treated Patients (IGSLI). According to their recurrence-related response to long-term lithium prophylaxis, patien ts were classified into three groups: excellent (n = 45), moderate (n = 81) and poor responders (n = 41). Only depressive episodes resulting into hosp italisation were considered. A marked reduction in the number of suicide at tempts was observed in the excellent lithium responders. However, we also f ound that over 80% of moderate responders and nearly 50% of poor responders did not exhibit any further suicidal behaviour during lithium treatment. F urthermore, we could demonstrate a significant reduction of suicide attempt s per year as compared to a corresponding pre-lithium period in all three g roups (0.10 vs. 0.33, 0.06 vs. 0.27, 0.02 vs. 0.26). There were four suicid es in this high-risk group, corresponding to a suicide-related standardised mortality ratio (SMR) of 13.7. This contrasts sharply with an expected sui cide SMR of approx. 100 in this population. Suicide risk was not related to the recurrence-preventing effect. Conclusion: The reduction in suicide att empts, in both responders and non-responders, indicates that lithium posses ses a specific anti-suicidal effect besides its mood-stabilising property.