Prognosis of depression: depressive course and trajectories of functional and work disabilities (WC2005-048)

Background

Starting date: 01/11/2005

Mood disorder is a highly prevalent disabling disorder that frequently runs a chronic course with a number of negative health care consequences, including decreased quality of life or productivity, and increased medical consumption, disability, psychiatric and somatic morbidity and mortality (Andrade et al. 2003; Spijker et al 2001; Beekman et al 1997; Penninx et al 1999). Given an extremely variable natural history, the most viable route for prevention is to design ways to detect those at risk for an unfavourable prognosis in an early stage, tailoring interventions to the projected prognosis. A first requirement for any such preventative action is to have detailed knowledge of the long-term prognosis of mood disorders. Given the undisputed relevance for public health, it is surprising how little is known about the short- and long-term course of various depression disorders. Both from a clinical and a public health perspective accurate data on the prognosis are necessary to be able to plan and monitor treatment and to inform patients. Theoretically, the concept of the course of depression is not well studied. Recent work suggests that a simple disease-episode model is not adequate to understand the course. In clinical practice and in the trial literature, the disease model of the prognosis of depression predominates, probably leading to overly optimistic expectations with regard to the prognosis. Moreover, given the pleiomorphic natural history, the course of depression may be better understood in terms of a fluctuating expression of a chronic underlying disposition toward experiencing negative cognitions, affect, and avoiding behaviour. Few studies have systematically combined a categorical with a dimensional definition and measurement of depression, that included subjects at different levels of vulnerability and phase of illness and followed them over time. Most of the (few) studies in this area do involve major depression, but regarding other depressive disorders (dysthymia, minor depression) such studies are absent.

There have been some studies that explored the importance of demographic and clinical factors on the course of depressive disorders. Again, however, since there are not so many studies that have explored the course of various types of depressive disorders, also the information on potential demographic and psychiatric-clinical variation of the course and consequences of depressive disorders is scarce. A few studies have described that the course of depression may be worse for women than for men and for older versus younger persons (Mojtabai R et al, 2004; Bracke P 2000), but these data are sometimes contradicted by other studies. For major depression, a higher severity of depressive symptoms at baseline, longer duration of previous episodes, and a history of multiple negative life events have been found to be associated with a worse prognosis (Spijker et al. 2002), but how these data exactly relates to other psychiatric-clinical information (personal history, family history etc) and whether these data are also as important in the prediction of the course of minor depression and dysthymia has been unresolved.
Public health consequences of depression ranging from impact on the well-being and daily functioning of patients, to severe economic consequences and impact on mortality, are now well-established. However, the course of these public health consequences has been much less examined, especially for dysthymia and minor depression. The trial literature tends to focus on the symptoms of the disorder when evaluating outcomes. From a patient and public health perspective, data on the trajectory of outcome in terms of well being, functioning, co-morbidity and economic consequences are equally important but much less studied. Several epidemiological studies have shown that fluctuating symptom levels correlate strongly with fluctuating levels of well being and disability. However, data on the (long-term) course of public health effects of various depression disorders are scarce. Finally, the potential impact that demographic and psychiatric-clinical factors may have in determining the public health consequences of depression has not been largely examined.