Depression is a highly prevalent condition that results in substantial functional impairment. Advocates have attempted in recent years to make the 'business case' for investing in quality improvement efforts in depression care, particularly in primary care settings. The business case suggests that the costs of depression treatment may be offset by gains in worker productivity and/or reductions in other healthcare spending. In this paper, we review the evidence in support of this argument for improving the quality of depression treatment. We examined the impact of depression on two of the primary drivers of the societal burden of depression: healthcare utilisation and worker productivity. Depression leads to higher healthcare utilisation and spending, most of which is not the result of depression treatment costs. Depression is also a leading cause of absenteeism and reduced productivity at work. It is clear that the economic burden of depression is substantial; however, critical gaps in the literature remain and need to be addressed. For instance, we do not know the economic burden of untreated and/or inappropriately treated versus appropriately treated depression. There remain considerable problems with access to and quality of depression treatment. Progress has been made in terms of access to care, but quality of care is seldom consistent with national treatment guidelines. A wide range of effective treatments and care programmes for depression are available, yet rigorously tested clinical models to improve depression care have not been widely adopted by healthcare systems. Barriers to improving depression care exist at the patient, healthcare provider, practice, plan and purchaser levels, and may be both economic and non-economic. Studies evaluating interventions to improve the quality of depression treatment have found that the cost per QALY associated with improved depression care ranges from a low of 2519 US dollars to a high of 49,500 US dollars. We conclude from our review of the literature that effective treatment of depression is cost effective, but that evidence of a medical or productivity cost offset for depression treatment remains equivocal, and this points to the need for further research in this area.