Background: The current evidence base in Mental Health and Psychosocial Support (MHPSS) suggests that there is a need to address the complexity of the relationships between implementation and programme impact (Bangpan et al. 2015). Further examination of the links between programme features, delivery mechanisms and the effect of programme outcomes may benefit future programme development. Drawing on a broad range of evidence, and synthesising findings of different study designs offers opportunities to address the challenge to provide invaluable insights to inform policy and practice decisions.

Objectives: To present methods of combining findings from process and outcome evaluations to explore key mechanisms of effective MHPSS programmes.

Methods: We synthesised evidence from process and outcome evaluations using a Cross-Study Synthesis (CSS) approach. First, we synthesised qualitative data from process evaluations to identify key mechanisms or programme design potentially influencing the effectiveness of MHPSS programmes. Secondly, also performed a meta-analysis to evaluate the impact of MHPSS programmes. Thirdly, we coded the outcome evaluations to explore whether programmes have considered the identified key mechanisms when designing/delivering the programmes. Finally, we explored the key mechanisms in effective MHPSS programmes on PTSD and depression using meta-regression and comparative analysis of evidence .

Findings: We included 13 process evaluations and 46 outcome studies. Six key mechanisms were derived from process evaluation studies. The findings from CSS suggest that: 1) having trained providers in MHPSS programmes; 2) having socially adapted programme activities; or, 3) establishing good relationships with recipients, are key mechanisms of effective MHPSS programmes.
Conducting the CSS provides the opportunity to identify which key mechanisms generated by the process synthesis are currently being addressed by existing MHPSS programmes, and where there are gaps. It also supports a greater explorative analysis, identifying which mechanisms are associated with the impact of MHPSS to inform future programme development.