Circadian Light Sensitivity as a Mechanism for PTSD Vulnerability

Light regulates circadian rhythms, and unhealthy light exposure patterns have negative impacts on mental health. Disrupted circadian rhythms have been associated with posttraumatic stress disorder (PTSD), but the causal mechanisms are currently unknown. Our recent research indicates that the sensitivity of the circadian system to the disruptive effects of light at night likely plays a key role in PTSD development. This project will investigate the mechanistic hypothesis that light exposure at night increases the risk of developing PTSD after a traumatic event, and that people with higher light sensitivity are therefore at elevated risk. We propose four work packages to elucidate the physiological and genetic contributions of circadian light sensitivity and circadian disruption to PTSD risk. We will also test a highly feasible, cost-effective intervention designed to protect against PTSD by reducing disruptive effects of night light exposure on the circadian system in a randomised controlled trial. Our work will be guided by a PTSD Lived Experience Working Group. Beyond determining the causal mechanisms that implicate the circadian system in PTSD, our findings will enable new measures to identify individuals who are most likely to develop PTSD. This will lead to targeted countermeasures which could help to prevent PTSD onset.