The relationship between urinary melatonin metabolite excretion and posttraumatic symptoms following traumatic injury

Background: Associations between 24-hour urinary 6-sulphatoxy melatonin excretion and symptoms of posttraumatic stress disorder were assessed 2 days, 1 month and 6 months after traumatic injury requiring hospitalisation. Methods: Forty-eight participants were recruited following an admission to hospital for an acute traumatic injury. They completed assessments 48 h after the accident, 1 month and 6 months later. A 24-hour urine collection was initiated the morning before questionnaires were administered. PTSD symptoms and caseness was determined using the Impact of Event Scale (IES-R) and the Clinician Administered PTSD Scale respectively. Urinary 6-sulphatoxy melatonin was assayed by radioimmunoassay. Results: Mean age of participants was 34 years (SD = 12.72) and 75% were males. Ten (27%) participants met the criteria for PTSD 1 month post trauma and 6 (21%) met the criteria for PTSD at 6 months. Four of the six (67%) participants with PTSD at 6 months were also positive for major depression. Significant negative correlations were found between 6-sulphatoxy melatonin excretion at day 2 and all subscales and total score of the IES-R at the six month assessment. Controlling for depression, every one unit decrease in 6-sulphatoxy melatonin excretion was associated with a 13% increase in PTSD risk at six months (OR = 1.13, 95% CI 1.00-1.27). However, this association was lost when self-reported pain, gender and employment was added to the model (OR = 1.11, 0.93-1.32). Conclusion: This study provides preliminary data suggesting disrupted melatonin levels in the first 48 h following trauma may place individuals at increased risk of PTSD.