Return on investment from interventions to prevent common mental disorders among adolescents in Australia: A modelling study.

Objective: The prevalence of common mental disorders (CMDs, depression/anxiety) among Australian adolescents is increasing. Evidence is needed to inform how prevention efforts can be focused for greatest impact. This study used a compartmental model to estimate how investments could be optimally allocated across interventions to prevent CMDs in adolescents, and the corresponding health and economic benefits.

Methods: The Australian 0- to 19-year-old population was disaggregated by age (0-9, 10-14, 15-19), sex (male, female) and CMD experience (never, currently, previously). Twelve prevention interventions were included following targeted reviews. The model was calibrated to Australian population survey data and included sociodemographic risk factors from the literature that were relevant for included interventions (bullying, financial stress, poor school connectedness, racial discrimination, child maltreatment). An optimisation estimated how an additional AUD$50 million-AUD$1 billion per annum over 2024-2050 could be allocated across interventions to maximise the number of adolescents turning 20 without a lifetime experience of CMD.

Results: The benefit-cost ratios of interventions varied widely depending on whether they impacted CMDs directly or indirectly by reducing a risk factor, and also whether CMD was their primary purpose or not (e.g. poverty interventions). Optimally investing AUD$50 million-AUD$1 billion p.a. over 2024-2050 could lead to 144,577-791,277 fewer adolescents experiencing a CMD by age 20 (AUD$5064-AUD$18,507/lifetime CMD experience averted), with lower bound benefit-cost ratios ranging from 5.0 to 19.2. Optimally, budget allocations should include combinations of interventions targeting different age groups, sub-populations and risk factors.

Conclusions: Investing in evidence-based prevention interventions for adolescent mental health is likely to have a favourable return-on-investment.