The economic case for increased investment in the treatment of adolescents with common mental disorders in Colombia and South Africa.

Adolescence is a critical period for the emergence of mental health disorders. The prevalence of depression and anxiety among adolescents in high- and middle-income countries has increased over the past three decades. According to the Global Burden of Disease Study (2025), mental disorders account for 21.4% of the adolescent burden of disease in high socio-demographic index (SDI) countries and 16.1% and 18.6% in the middle- and low-SDI countries. Despite the high and rising burden, adolescent mental health remains less prioritized in policy and funding. Treatment rates in low- and middle-income countries are low, with fewer than one in ten affected adolescents receiving care in some settings. Poor mental health in adolescence is associated with long-term losses in educational attainment, productivity and social participation. There is growing evidence suggesting that mental health interventions for depression and anxiety can be cost-effective even in resource constrained settings. This paper presents new evidence on the return on investment from scaling up interventions for adolescent depression and anxiety in two middle-income countries: Colombia and South Africa. Using the OneHealth tool and an economic model previously applied in global adolescent investment cases, we estimate health, education and economic benefits under a scale-up scenario. Scaling-up treatment for depression and anxiety in Colombia results in a benefit-cost ratio (BCR) for economic benefits alone of 13.9 and for combined economic and social benefits of 15.4. For South Africa the BCRs are 13.0 and 13.9, respectively. Our findings offer policy-relevant evidence to support increased investment in adolescent mental health in settings where data and resources remain limited.