Parkinson's disease, DBS and suicide: a role for serotonin?

We would like to thank Temel et al . for their communication highlighting the potential role of serotonin and suicidal behaviours, which are intriguing and potentially of relevance. Temel et al . have previously shown that subthalamic nucleus (STN) HFS in a rat study inhibits serotonergic dorsal raphe firing rate and elicits depressive-like behaviour which can be prevented with pre-treatment with a serotonin reuptake inhibitor (Temel et al ., 2007). Post-mortem and biological challenge studies suggest serotonergic hyporesponsivity particularly in suicide attempts of high lethality and lower prefrontal serotonin receptor density with a compensatory increase in midbrain serotonin neuron density and function (Mann et al ., 1996; Oquendo et al ., 2003; Boldrini et al ., 2008). Temel et al . point to a potential mechanistic link between serotonin and post-surgical suicidal behaviours mediated via depression and impulsivity, which is less clear and very complex. In our paper, we identified an association between suicide attempts and post-STN HFS depression (Voon et al ., 2008). However, the link between STN HFS and depression is poorly understood in human studies and there are likely several different mechanisms leading to a similar depressive phenomenology. Post-surgical depression can be conceptualized as being mechanistically related to STN HFS itself, dopaminergic medication changes, psychosocial factors, Parkinson's disease-related depression or premorbid vulnerability to depression (Voon et al ., 2006). Temel et al . implicate STN HFS-related depression secondary to serotonergic inhibition, which may be one possible mechanism. The majority of STN …