Background: While Internet- and mobile-based interventions (IMIs) are potential options to increase the access to evidence-based therapies for post-traumatic stress disorder (PTSD), comprehensive knowledge on their working mechanisms is still scarce.

Objective: We aimed to evaluate studies investigating the efficacy and mechanisms of change in IMIs for adults with PTSD.

Although the concept of pathological grief dates back at least as far as Freud’s “Mourning and Melancholia”, there has been opposition to its recognition as a distinct mental disorder. Resistance has been overcome by evidence demonstrating that distinctive symptoms of prolonged grief disorder (PGD) – an attachment disturbance featuring yearning for the deceased, loss of meaning and identity disruption – can endure, prove distressing and disabling, and require targeted treatment.

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.