Post-traumatic stress disorder is a common condition that affects millions of people across the world. Up to date recommendations based on the best available evidence are vital to prevent and treat this debilitating condition. In this issue, we are bringing together a series of systematic reviews and meta-analyses that underpinned the development of the 2018 International Society for Traumatic Stress Studies Guidelines.

Background: Treatments for posttraumatic stress (PTS) are effective for many but not all people. There is a continued need to further our understanding of psychological mechanisms involved in the development and maintenance of PTS. Research has examined dysregulation of negative affect (NA) in PTS but relatively little attention has been paid to the role of dysregulation of positive affect (PA) in PTS.

Moral injury is the profound psychological distress which can arise following participating in, or witnessing, events which transgress an individual’s morals and include harming, betraying, or failure to help others, or being subjected to such events, e.g. being betrayed by leaders. It has been primarily researched in the military, but it also found in other professionals such as healthcare workers coping with the COVID-19 pandemic and civilians following a wide range of traumas.

Studies of posttraumatic stress disorder (PTSD) report volume abnormalities in multiple regions of the cerebral cortex.