Background Internationalevidence on the cost and effects of interventions for reducing the globalburden of depression remain scarce. Aims To estimate the population-level cost-effectiveness of evidence-based depression interventions and their contributiontowards reducingcurrent

Declaration of interest None. There is now widespread recognition of the immense burden that depression imposes on individuals, communities and health services throughout the world. Latest estimates from the Global Burden of Disease study GBD 2000 indicate that unipolar depressive disorders account for 4.4% of the global disease burden (65 million disability adjusted life years (DALYs) lost in total), in the same range as the total burden attributable to ischaemic heart disease, diarrhoeal diseases, or the combined impact of asthma and chronic obstructive pulmonary disease (World Health Organization, 2002; Ustun ̈ ̈ et al, 2004, this issue). What can be done to reduce this global burden, and at what cost? Although service access and treatment coverage remain low, there is growing empirical evidence from lowerincome as well as higher-income countries for the effectiveness and also cost-effectiveness of a range of pharmacological and psychosocial interventions for treating and managing depression (e.g. Chisholm et al, 2000; Schoenbaum et al, 2001; Simon et al, 2001; Araya et al, 2003; Patel et al, 2003). Using these and other data relating to the epidemiological burden of depression, the clinical outcomes associated with different interventions and the economic costs of treatment, this analysis set out to inform mental health policy and planning through the provision of a population-level assessment of cost-effectiveness for different regions of the world.