Abstract: The death of the loved one is one of the important turning points of people's life. Although most people can recover from bereavement without professional help, a few bereaved people might experience a wide range of mental disorders, including depression, prolonged grief disorder, and posttraumatic stress disorder. The supply of traditional bereavement psychological services is far from meeting the demand of these people. In recent years, Internet-based interventions have gradually been applied to improve the mental health of bereaved people. They can provide therapy for more people, which may greatly ease the imbalance between supply and demand. Systematically investigating the effectiveness of Internet-based interventions for bereaved people and what will influence their effectiveness helps guide clinical practice. However, although there were two reviews on the effectiveness of internet-based intervention for bereaved people, they only relied on a small number of studies published before 2021. With a sudden upsurge in online psychotherapeutic intervention during the COVID-19 pandemic and the growing interest in psychotherapy research for internet-based interventions, more studies were published and needed to be included. In addition, the investigation of moderating effects on the effectiveness of internet-based interventions for bereaved people was still missing. Thus, this study conducted a systematic review and meta-analysis aims to examine the effectiveness of Internet-based mental-health interventions for bereaved people and explore whether the effectiveness was influenced by intervention theories, intervention strategies (the use of exposure, cognitive reappraisal, behavioral activation, or meaning reconstruction within the intervention), the number of sessions, frequency of session completion, therapeutic feedback, the reminder, and dropout rate.
Systematic searches were conducted in PubMed, PsycINFO, EMBASE, CINAHL, Scopus, Web of Science, CNKI (China National Knowledge Infrastructure), WFD (Wanfang Data), and Weipu database. Then, we searched reference lists and bibliographies of all included articles to ascertain articles not retrieved by the primary search. Comprehensive Meta-Analysis 3 was used for meta-analysis. Publication bias was assessed by funnel plots, Egger's regression test, and the trim and fill technique.
47 studies of Internet-based interventions for bereaved people were included in the systematic review through literature search and screening, of which 19 randomized controlled trials met the criteria of meta-analysis (N = 1222 participants). The meta-analysis included a total of 68 effect sizes. The results showed that the interventions had a significant moderate effect on mental health (g = 0.54; 95% CI = [0.39, 0.70]). Specifically, the interventions showed significant moderate effects for symptoms of pathologic grief (g = 0.56; 95% CI = [0.39, 0.74]), depression (g = 0.51; 95% CI = [0.36, 0.67]), and posttraumatic stress disorder (g = 0.63; 95% CI = [0.45, 0.81]). In terms of improving mental health, the effectiveness of Internet-based interventions for bereaved people was moderated by the use of meaning reconstruction, the number of sessions, frequency of session completion, and therapeutic feedback. Without using meaning reconstruction, having 10 sessions or more, and therapeutic feedback was associated with a larger effect of the Internet-based interventions, and contacting more than once a week showed a stronger effect than once a week. However, whether an intervention was based on cognitive behavior therapy, set reminders, had a high or low dropout rate, included exposure exercises, cognitive reconstruction, or behavioral activation had no moderating effect.
This study shows that Internet-based interventions have positive effects on improving the mental health of bereaved people and have different effects under different conditions. It supports that Internet-based interventions can be used as alternative options to face-to-face intervention for bereaved people to alleviate the problem of lacking bereavement service resources, which helps promote Internet-based interventions for bereaved people in clinical practice in China. Additionally, it provides directions for how to develop more effective Internet-based interventions for bereaved people in the future.

Key words: bereavement, Internet-based intervention, pathologic grief, posttraumatic stress disorder, depression