Research in humanitarian settings – referred to here as areas affected by disasters and armed conflicts – has shown diverse impacts of such crises on the mental health and psychosocial well-being of populations. These consequences range from resilience (good mental health despite exposure to significant adversity), non-disordered psychological distress, to increased mental disorders, including anxiety (eg, post-traumatic stress disorder (PTSD)), depressive, and substance use disorders.1,–,3 In addition, mental health practitioners in humanitarian settings frequently encounter people with severe pre-existing neuropsychiatric disorders (eg, psychotic disorders and epilepsy).4 Moreover, disasters and armed conflicts have been shown to impact the social conditions that shape mental health, through increased poverty, threats to human rights, domestic and community violence and changed social relations.5

To address negative impacts, mental health and psychosocial support (MHPSS) programmes are increasingly a standard component of humanitarian response. MHPSS has been defined as ‘any type of local or outside support that aims to protect or promote psychosocial well-being and/or prevent or treat mental disorder’.6 There appears to be increasing consensus on best practices, as indicated by the publication of two sets of international guidelines; the 2007 Inter-Agency Standing Committee Guidelines on Mental Health and Psychosocial Support in Emergency Settings6 and the 2011 Sphere Handbook.7

In this editorial, we discuss the emerging field of MHPSS from the perspective of evidence-based practice. We describe challenges to evidence-based MHPSS practice, and highlight areas where concerted action may either (A) improve the quality of MHPSS programming (by basing decision-making on research findings) and/or (B) improve MHPSS research efforts (by making the pursuit of reliable and valid knowledge more responsive to needs of affected populations). We structure the discussion in accordance with steps of the programme cycle where empirical evidence may support decision-making, that is needs …