Concretism in biological suicide research -- are we eating the menu instead of the meal? Some thoughts on present research strategies.

Research into serotonergic parameters associated with suicidal behaviour has resulted in many inconsistent and ambiguous findings. In this mini-review, we have tried to name some examples of methodological and conceptual vagueness and pitfalls in biological suicide research. The existing literature indicates various critical issues considered when interpreting existing data in this area: -- The 'suicidality' construct is not useful in biological suicide research. Autodestructive tendencies mostly occur in suicide completers and are probably not found in many suicide attempters and individuals with suicidal thoughts. No consistent association has been found between suicide intent and injury, suicide intent and suicide risk, choice of suicide method (violent vs. non-violent) and suicide risk, suicidal thoughts or attempted suicide. No close relationship between different degrees and different forms of suicidal behaviour has yet been demonstrated with any degree of consistency. According to many studies, serotonergic markers do not correlate with the various qualities and intensities of suicidal behaviour. -- The association between suicidality and impulsivity or aggression is weak. There probably is a disturbance in impulse and aggression control, but only in a subgroup of'suicidal' patients. -- It might be misleading to use nosological constructs of depression in order to characterize suicidal individuals in biological suicide research. Biological variables might be associated with specific depressive symptoms, but not with some nosological construct or the sum score of a depression rating scale. -- The alleged association between peripheral and central serotonergic parameters is based on assumptions for which there is insufficient proof. Several studies indicate that there is no correlation between changes in central and peripheral serotonergic parameters. The mechanism of changes of peripheral serotonergic parameters is not sufficiently understood.