Platelet serotonin as biomarker for assessing suicidal behaviour in patients with bipolar I disorder

Context. Suicide is a global public health issue. Bipolar disorder (BPD) has the highest suicide risk among individuals suffering from mental disorders. Serotoninergic dysfunctions have been linked to suicidal behaviour and platelet serotonin is recognised as a reliable index for the presynaptic serotonin activity.

Objective. Our aim was to assess whether alterations occur in platelet serotonin concentrations in BPD type I in respect to suicide attempters compared with nonattempters.

Design. This was a cross-sectional, observational study.

Subjects and Methods. Plasma platelet serotonin concentrations were measured using ELISA technique in 71 BPD I patients. The participants were assigned into 3 groups (non-attempters, low lethality and high lethality suicide attempters), according to the Columbia-Suicide Severity Rating Scale. Socio-demographical and clinical data was obtained by using MINI 6.0 and a semi-structured questionnaire designed specifically for this research.

Results. Our study showed significant lower levels of platelet serotonin in suicide attempters compared with non-attempters (p = 0.030) and in high-lethality attempters compared with low-lethality attempters (p = 0.015). The study recorded a higher number of total lifetime and lifetime depressive episodes for suicide attempters with BPD I.

Conclusions. Our results subscribe to the importance of platelet serotonin as a reliable biomarker in suicide risk assessment.