Adolescence is a critical life stage where the foundations of lifelong health and wellbeing are laid. It is now well-established that most serious mental disorders that disable or kill in adult life have an onset between the ages of 12-25, with over half having an onset before the age of 16.

While disorders such as anxiety, depression and psychosis have an adolescent onset their recognition is often delayed, and interventions, when offered, are often 'late'; only when the disorders have become established and disability set in.

The majority of adolescents live in low- and middle-income countries (LMIC) where resources are scarce, the stigma of ill-health high, and the most vulnerable are at the greatest disadvantage. There is a frequent association between mental health problems and physical problems, especially those related to nutrition, both undernutrition and obesity.

The most common non-communicable disorders (NCDs) of adolescence, and their greatest burden, is hence related to a combination of mental ill-health and nutrition-related problems. It is well-established from work in high-income countries that such disorders can be prevented and, if identified early, be treated with low-intensity interventions to prevent chronicity and continuity into adult life.

The ISOBAR project aims to implement evidence-based interventions in school-settings in two LMICs, India and Nigeria. The project team has extensive experience in working with young people in school-settings in these countries. Our previous work in these countries has shown that while many adolescents suffer from such disorders and see schools as places where they would seek help, almost no state-funded school in such settings offers any health programmes that promote positive health and prevent serious disorders from emerging.

We aim to recruit and train school-based counsellors in evidence-based interventions which have been tailored to local socio-cultural context and offer these in a staggered manner to three schools at each site (two in India, one in Nigeria). We will conduct this work in an equitable partnership with schools, young people, their carers, local community organisations, health providers and policymakers who have strong and well-established links.

Using an implementation research framework, we will evaluate our programme for whether it is acceptable to the local community, useful in promoting positive health, preventing serious disorders from emerging, and ensuring that those who need specialist care receive it in a timely and effective manner. We will determine the costs and benefits of our intervention and explore factors that affect its sustainability beyond the lifetime of our project.

The work will leave a lasting legacy that has the potential to transform the health and well-being of millions of adolescents in the developing world