Psychological First Aid in Humanitarian Emergencies: A Systematic Review of Intervention Effectiveness, Strengths and Weaknesses Applying the LISTEN Big Qualitative Data Method

Background: Psychological First Aid (PFA) is one of the most widely disseminated mental health and psychosocial support (MHPSS) interventions in humanitarian emergencies. Yet despite its global uptake, evidence on its effectiveness remains fragmented, and little is known about which aspects of PFA work well, or fail, in crisis settings. Methods: We conducted a systematic review using the LISTEN method, which integrates collaborative qualitative analysis with digital text-network analysis to synthesise large, heterogeneous datasets. We searched three peer-reviewed databases and two grey literature databases, and key humanitarian organisations’ websites. One hundred publications met inclusion criteria. We examined co-occurring patterns in PFA reported strengths, weaknesses and effectiveness indicators, and incorporated insights from experts by experience to contextualise findings.Results: Across studies, early, low-threshold support was the most consistently reported strength, closely linked to accessibility, service integration and reduced burden on overstretched health systems. Weaknesses clustered around insufficient provider training, limited evaluation capacity and inconsistent definitions of what constitutes PFA. Although many studies reported reduced distress and positive participant feedback, only 16% used validated mental health measures. Stakeholders emphasised that several interventions labelled as PFA deviated from the core model, particularly when delivered as multi-session programmes rather than a rapid response within 72 hours. Text-network analysis highlighted strong associations between training gaps and weaker effectiveness outcomes.Conclusion: PFA interventions show promise in humanitarian emergency contexts, particularly in providing rapid, accessible support. However, inconsistency in definitions and over-reliance on acceptability rather than high quality evaluations limit effectiveness conclusions. Strengthening training, embedding standardised outcome measures, and clarifying PFA models are essential for improving practice. LISTEN offers a scalable approach for synthesising evidence in time-sensitive humanitarian contexts. The development of innovative research methods and incorporating experts by experience in research processes has proven key to contextualise findings with field-based realities.