Using data from over two decades of Young Lives research in Peru, India and Ethiopia, this paper shows that risk and protective factors accumulate over the life course.

Key findings:

• Reported symptoms of anxiety and depression vary significantly across countries and over time, with Peru exhibiting the highest prevalence, Ethiopia showing post-conflict deterioration and India remaining relatively stable.
• Gender disparities are substantial, with women reporting significantly worse mental health in Peru and India.
• Early-life conditions such as caregiver mental health and household wealth are linked to later mental health. During adolescence, strong social relationships and a sense of pride are protective factors. In young adulthood, personality traits—especially neuroticism—are consistently associated with worse mental health, while grit shows positive associations in India.
• Economic shocks (e.g., job loss, food insecurity, crop failure) and experiences of violence, including intimate partner violence and conflict-related violence in Ethiopia, emerge as strong risk factors for mental health.
• While some factors associated with mental health are consistent across countries, others are highly context-specific, emphasising the importance of local economic and social conditions.

The evidence underscores the need for comprehensive, context-sensitive, gender-sensitive mental health policies that address risks from early stages.