New knowledge has emerged about decision-making, mood regulation, social distortions and learning that is relevant for the diathesis for suicidal behavior. All four domains have identified underlying neural circuits and for decision-making and mood regulation also specific neurotransmitter systems.

We have conducted PET studies of the serotonergic system and CSF studies of the serotonin, norepinephrine and dopamine neurotransmitter systems in patients surviving suicide attempts to determine whether they have neurotransmitter abnormalities that resemble those found in the brain after suicide. We found alterations in the serotonin transporter and the 5-HT_1A receptor that are similar to those seen in suicides and moreover the severity of the abnormality in 5-HT_1A binding is correlated with the lethality of suicidal behavior. Other studies examining CSF levels of 5-HIAA are consistent with imaging data and extend the findings to the noradrenergic and dopaminergic systems. Finally, we will present data on use of these biomarkers to predict treatment outcome. Abnormal decision-making and mood regulation in suicidal patients is linked to abnormal brain biology and has direct implications for clinical practice in terms of selecting specific types of medication and how these may be best combined with psychotherapies.