Protocol for a systematic review to understand the long-term mental-health effects of influenza pandemics in the pre-COVID-19 era

Abstract

Aims: This protocol describes a forthcoming systematic review of the question: ‘What are the long-term effects of historical influenza pandemics on mental health, resulting either from illness itself or the social or economic effects of pandemics and public health responses?’ Methods: We will review studies that investigate associations between influenza pandemics and long-term mental-health impacts. Following the PICO framework, populations (P) may include those with and without pre-existing mental-health symptoms or conditions. Intervention (I) is exposure to an influenza pandemic during the study period encompassing five pandemics (1889–2009). Comparators or controls (C) are not applicable. The review will address outcomes (O) of mental-health morbidity from direct infection and/or related circumstances, including, for example, receiving a disability pension, institutionalisation and/or death. Results: Due to societal disruptions, illness and bereavement during pandemics, many people are likely to be affected in myriad ways. Therefore, investigation into mental-health consequences should not be restricted by risk group or diagnosis. To our knowledge, this protocol and forthcoming systematic review are the first to include studies for broad populations and multiple measures of mental-health morbidity. The historical perspective and comparison of pandemics with varying severity but assumed similar causative pathogens also enable insights into the consistency of long-term consequences across pandemics. Conclusions: Pandemics likely produce long-term mental-health impacts with relevance for social, health and economic planning. The systematic review based on this protocol will complement other evidence on pandemic impacts and help policymakers incorporate relevant interventions.