The influence of Executive Function on Mental Health in vulnerable adolescents: a multi-site low and middle income country approach Executive function (EF) regulates emotions, thoughts and behaviours, and difficulties in EF have been strongly implicated in mental health problems in high income countries (HICs). EF includes a set of cognitive skills such as working memory, cognitive flexibility, selective attention and inhibition which form the building blocks for higher order cognitive functions such as reasoning, planning every day activities and problem solving. EF is therefore critical in emotional, behavioural, cognitive, and social functioning and interpersonal relationships.  Poor EF has wide ranging implications in a number of important areas; in particular, it is associated with increased rates of mental health disorders such as depression, anxiety and attention deficit hyperactivity disorder. There are two periods during which development of EF is rapid; childhood and adolescence. These are critical time points to intervene and prevent impairments in EF.  Poor EF can result from biomedical factors, such as poor nutrition or exposure to HIV and malaria or from exposure to poverty, particularly when this occurs during periods of rapid EF development. These risk factors will affect both individuals' performance on EF tasks as well as the neural substrates of EF. The high level of socioeconomic adversity and the presence of multiple risk factors will have a strong influence on adolescents' achieving their potential and will impact their contributions to society through employment, social functioning, mental and physical health.   Investigators across multiple Departments at the University of Oxford have over a number of years concentrated on the relationship between EF, mental health and risk taking behaviours such as (unprotected sex, alcohol or drug use). Research in this area is being carried out in collaboration with investigators in multiple Low and Middle Income Countries (LMIC): by Abubakar and Newton in Kenya; Kahn, Scerif, Demeyere and Stein in South Africa; Favara, Sanchez and Pankhurst in Ethiopia and Peru.   This proposal will create a platform for UK and LMIC researchers working on EF and mental health, the harmonisation of EF tools currently used across sites and it will enable the piloting of a new EF measure to allow for the comparison of EF and its association with mental health data across sites. A number of studies have shown that EF can be improved in children and adolescents either through direct stimulation (e.g. EF-specific training tasks) or through enhancing their psychosocial environment, but not all these interventions may be financially viable or culturally acceptable in LMICs. A necessary step before intervening is to ensure we have accurate tools which reliably measure EF across settings and cultures, and that the cultural acceptability of relevant interventions is assessed.  As part of this proposal, we will refine our measurement tools and investigate contextually appropriate interventions to improve EF, during one of the critical periods of EF development i.e. adolescence. Improving EF in adolescence will ensure they will be able to take advantage of school education and it will allow for informed relational and occupational choices, as well as reduce the risk of high-risk sexual and substance use behaviours and promote physical and mental health. The Global Challenges Research Fund (GCRF) supports cutting-edge research to address challenges faced by developing countries. The fund addresses the UN sustainable development goals. It aims to maximise the impact of research and innovation to improve lives and opportunity in the developing world.