Low platelet-poor plasma concentrations of serotonin in patients with combat-related posttraumatic stress disorder

Background: Combat-related posttraumatic stress disorder (CR-PTSD) is associated with a dysregulation of various neurotransmitter systems. Methods: We assessed levels of platelet-poor plasma (PPP) norepinephrine (NE), and serotonin (5-HT), and 24-hour urinary excretion of NE, dopamine (DA), and homovanillic acid (HVA) in 17 male outpatients with untreated chronic CR-PTSD (age, 33.1 ± 7.4 years) and 10 normal control subjects (age, 35.8 ± 2.7 years). Results: Compared with the control subjects, the PTSD patients showed significantly lower PPP 5-HT levels, elevated PPP NE levels, and significantly higher mean 24-hour urinary excretion of all three catecholamines (NE, DA, and HVA). The 24-hour urinary HVA values of the CR-PTSD patients correlated significantly and positively with the total Impact of Event Scale scores and the avoidance symptoms cluster scores, and the PPP 5-HT levels correlated negatively with the Hamilton Anxiety Rating Scale scores. The PPP NE/5-HT ratio was significantly higher in the study group than in the control subjects. Conclusions: We believe this combined enhanced noradrenergic activity and diminished 5-HT activity may be relevant to the neurobiology of CR-PTSD.