Depression is among the most prevalent of mental disorders and is one the leading causes of disability worldwide (World Health Organization, 1996). A study across six countries found that patients with higher scores for depressive symptoms had worse health, functional status, quality of life and greater use of health services across all sites (Herrman et al, 2002). This chapter provides an overview of the issues and methods involved in the assessment of depressive symptoms in adults and older persons; different factors and methods are required for younger consumers.

Why assess outcomes?

Given its often erratic and relapsing course, the assessment of the quality and severity of depression is important for a number of reasons. These have been divided by Hickie et al (2002) into two groups: clinical and evaluative. The clinical reasons comprise: enhancing the involvement of consumers in their own treatment; documenting a range of clinically relevant aspects of life; improving the identification of early relapse; comparing responses to different treatments; improving understanding of short- and long-term outcomes; and alerting the clinician to a possible need to change the treatment or management. Their list of non-clinical purposes include: evaluating new treatments; contributing to assessment of cost-effectiveness; understanding variations in quality and access to services; and evaluating the impact of major health service innovations and specific policy initiatives. This is an impressive list of reasons for measuring outcomes in depression, to which we add a few of our own. Depression, like most mental disorders, has an effect beyond the index consumer. In addition to the mental pain of the condition itself, there is often ‘collateral damage’ to family members in terms of worry, burden of care and impaired child care, as well as to society at large in terms of lost productivity and treatment costs. Certain forms of outcome measure can target some of these effects. Also, it is known that not all aspects of the depressed state recover at the same rate (see below). By formally assessing domains beyond primary symptoms, one can assess wider aspects of recovery, such as social and occupational functioning.