Re: Antisuicidal effects of lithium - bias in interpreting the effectiveness of lithium
EDITOR-Mueller-Oerlinghausen makes a causal statement about the link between lithium prophylaxis and suicide prevention (1), whereas the evidence is only correlational. The strength of Joanna Moncrieff’s critique of lithium is the scepticism she has for the literature and her recognition of the bias, such as that displayed by Mueller-Oerlinghausen, for favourable interpretation of the effectiveness of lithium.
The evidence about suicide prevention to which Mueller-Oerlinghausen refers includes the finding that patients prescribed long-term lithium do not have increased mortality, particularly due to suicide, generally found in patients with manic-depressive disorder (2,3). Such results, of course, should be understood with caution, not least because patients in these studies might be unusual in some way. Compliant, consistent attenders at dedicated lithium clinics are not necessarily typical of all patients on lithium. In an unselected sample of patients treated with lithium for more than 2 months, excess mortality was found to be similar to that noted in earlier studies of manic-depressive patients before lithium was widely introduced (4).
Similarly, there should be reservations about the finding that the mortality of patients who discontinue lithium treatment is significantly higher than those in the general population (5). Patients who drop out of treatment may be more at risk of suicide because of factors unrelated to lithium treatment.
Propagating spurious conclusions about the effectiveness of lithium encourages dependence on this medication. Further randomised controlled trials measuring degree of unblinding are required to help clarify the extent to which lithium is placebo treatment.
D B Double, Consultant Psychiatrist, Norfolk Mental Health Care, Hellesdon Hospital, Drayton High Road, Norwich NR6 5BE. (Duncan_Double@bigfoot.com)
1. Mueller-Oerlinghausen B. Re: Antisuicidal effects of lithium. http://www.bmj.com/cgi/eletters/316/7141/1330#EL6
2. Coppen A, Standish-Barry H, Bailey J, Houston G, Silcocks P, Hermon C. Does lithium reduce the mortality of recurrent mood disorders? J Affect Dis 1991;23:1-7.
3. Mueller-Oerlinghausen B, Ahrens B, Grof E, Grof P, Lenz G, Schou M, Simhandl C, Thau K, Volk J, Wolf R, Wolf T. The effect of long-term lithium treatment on the mortality of patients with manic-depressive and schizoaffective illness. Acta Psychiatr Scand 1992;86:218-222.
4. Norton B, Whalley LJ. Mortality of a lithium-treated population. Br J Psychiatr 1984;145:277-282.
5. Mueller-Oerlinghausen B, Wolf T, Ahrens B, Glaenz T, Schou M, Grof E, Grof P, Lenz G, Simhandl C, Thau K, Vestergaard P, Wolf R. Mortality of patients who dropped out from regular lithium prophylaxis: a collaborative study of the International Group for the Study of Lithium_Treated Patients (IGSLI). Acta Psychiatr Scand 1996; 94:344-347
Competing interests: No competing interests