Seeking for biological markers in suicidal behaviour.

Abstract

Suicidal behaviour still represents a serious public health problem. Although the existence of some consultations on this subject, their efficacy remains very far from what we wish. In that sense, the research on the biological markers of suicidal behaviour might be of considerable importance. The aim of this paper is to present the biological systems involved on suicidal behaviour and to discuss if they can be used as a group of biological tests which could help clinical interview in predicting and preventing this kind of behaviour. It was done a Medline search between 1989 and 2007, considering the key-words Neurobiology and Suicide and therefore forty original or review articles were selected after reading each abstract content. From all the biological systems studied the one which shows more convincing data about its involvement in suicide is the serotoninergic system. At this level, we can say that there is a decreased neurotransmission of this monoamine in the Central Nervous System and Platelets as well as a compensatory increased binding of ligands to the serotoninergic receptors. At the same time, we have an hyperactivation of the HPA axis with lack of normalization of the Dexametasone Supression Test, decrease of neurotrophic genes like CREB, NT-3 and BDNF on some regions of the brain and of molecules from the lipidic metabolism, all of them capable of down-regulating the serotoninergic neurotransmission. These results are found in different pathologies with suicidal features, which make us think about a specific Neurobiology of Suicide. On the other hand, genetic polymorphisms of genes like the serotonin transporter, Tryptophan hydroxilase and 5-HT2a receptor seem to be significantly associated to suicide. Others, like the dopaminergic and noradrenergic systems are possible candidates to play a role on this behaviour but these studies need further replication. Finally, we can say that about the endocannabinoid, thyroid hormones, glia and opioid receptors systems there are already the first results of their involvement on suicide but these are very preliminary data. In conclusion, we consider that as this is a largely heterogenous kind of behavior, clinical practice could, potentially, be assisted by a group of biological tests capable of making the clinical cases more objective, which in turn would allowed us to diagnose large nosographic groups of patients instead of specific categories. In other words, it would be possible to increase sensibility but at the same time decrease specificity.