Depression is a leading cause of burden of disease and health care costs 
. Worldwide, depression ranks third on the list of leading causes of burden of disease, causing over 4 percent of all disability adjusted life years (DALYs), and it is projected to rank first on this list by 2030 
. For middle- and high-income countries, depression was already the leading cause of burden of disease in 2004, causing over five and eight percent of all DALYs, respectively 
. In the Netherlands, almost four percent of the burden of disease is caused by depression 
, and the 12 month prevalence of depression is 5.4% 
. These rates compare to other European countries 
. For the Netherlands, it is estimated that the direct medical costs of depression are 773 million euros (1.1% of total costs of illness in the Netherlands) 
Effective prevention of major depression has the potential to reduce the burden of disease considerably. Three types of prevention can be discerned, depending on the target group of the intervention: universal (targeted at entire populations), selective (targeted at high-risk groups), or indicated (targeted at individuals with depressive symptoms not meeting all criteria for a depressive disorder). An important reason for targeting prevention at people with sub-threshold (minor) depression is that they have an increased risk of developing major depression compared to persons not meeting the criteria of sub-threshold depression 
. In addition, sub-threshold depression is associated with impaired functioning, reduced quality of life, and excess medical and non-medical costs 
Various types of psychotherapy have been evaluated not only to cure depressive episodes but also to prevent first and further episodes 
. A recent meta-analysis attributed a statistically significant reduction of 22% in the incidence of depressive disorders to psychological interventions 
. This meta-analysis included all types of prevention (universal, selective, and indicated). A meta-analysis of indicated prevention of major depression in individuals with sub-threshold depression only, found a risk reduction of 30%, but this was not statistically significant 
. Cognitive behavioural therapy in the form of a ‘Coping with depression’ course was in several studies found to result in a reduced risk of getting major depression of 38% 
. So, effective prevention of major depression has the potential to reduce the burden of disease considerably.
In a Dutch trial, minimal contact psychotherapy, based on Lewinsohn's ‘Coping with depression’ course, prevented one third of the incidence of major depression in individuals with sub-threshold depression 
. As this specific delivery format of the ‘Coping with Depression’ course requires little effort and therapists' time, it seems attractive from an economic point of view. Moreover, the bibliotherapeutical format introduces some additional benefits: it is a low threshold intervention, with no fear of stigma involved; it focuses on empowering the participants by improving self-management skills; and it can be conducted at times that agree best with the participant's agenda.
Although the evidence base for effectiveness of depression prevention is growing, evidence for its cost-effectiveness is still scarce. To our knowledge, few economic evaluations of preventive interventions for depression have been published. Smit et al. evaluated the cost-effectiveness of MCP in costs per avoided major depression episode, with a one year time horizon, not including the costs of screening for eligible participants 
. Lynch et al. performed an economic evaluation as part of a trial in which the effectiveness of a CBT course for the prevention of depression in adolescents with depressed parents 
. Vos et al. published cost-effectiveness analyses of several depression interventions, including relapse prevention by maintenance treatment 
. In this paper, we estimated the costs and benefits of opportunistic screening in general practice and treatment with minimal contact psychotherapy for individuals with sub-threshold depression to prevent the incidence of depressive disorders in those individuals.