Some problems of research on the association between blood types and suicide mortality: comment on Lester (2004)

This is a comment on the ecological finding of a negative association of national suicide rate and national proportion of people with Type O blood (Lester, 2004). Current knowledge on this topic is reviewed and several problems, limitations, and discrepancies within this research line are noted. Specifically, it is suggested that (1) this association appears to have been subject to attenuation recently; (2) available ecological evidence on this association is contradictory to both individual-level findings on the same topic and similar ecological-level findings pertaining to personality-related risk factors and antecedents of suicide; (3) a negative association of one of the four ABO phenotypes with suicide mortality does not help single out phenotypes with possibly increased suicide risk; and (4) genetic suicide risk factors may well be associated with other ABO phenotypes than Type O and may further coincide with other blood polymorphisms than the ABO system.