World Health Organization's low-intensity psychosocial interventions: a systematic review and meta-analysis of the effects of Problem Management Plus and Step-by-Step.

Many societies have been recently exposed to humanitarian and health emergencies, which have resulted in a large number of people experiencing significant distress and being at risk to develop mental disorders such as depression, anxiety and post-traumatic stress disorder. The World Health Organization has released a series of scalable psychosocial interventions for people impaired by distress in communities exposed to adversities. Prominent among these is a low-intensity transdiagnostic psychosocial intervention, Problem Management Plus (PM+), and its digital adaptation Step-by-Step (SbS). This systematic review is the first to summarize the available evidence on the effects of PM+ and SbS. Up to March 8, 2023, five databases were searched for randomized controlled trials examining the effects of PM+ or SbS on distress indicators (i.e., general distress; anxiety, depressive or post-traumatic stress disorder symptoms; functional impairment, self-identified problems) and positive mental health outcomes (i.e., well-being, quality of life, social support/relationships). We performed random-effects multilevel meta-analyses on standardized mean differences (SMDs) at post-intervention and short-term follow-up assessments. Our search yielded 23 eligible studies, including 5,298 participants. We found a small to medium favorable effect on distress indicators (SMD=-0.45, 95% CI: -0.56 to -0.34) and a small beneficial effect on positive mental health outcomes (SMD=0.31, 95% CI: 0.14-0.47), which both remained significant at follow-up assessment and were robust in sensitivity analyses. However, our analyses pointed to substantial between-study heterogeneity, which was only partially explained by moderators, and the certainty of evidence was very low across all outcomes. These results provide evidence for the effectiveness of PM+ and SbS in reducing distress indicators and promoting positive mental health in populations exposed to adversities, but a larger high-quality evidence base is needed, as well as research on participant-level moderators of the effects of these interventions, their suitability for stepped-care programs, and their cost-effectiveness.