 |
 |
 |
|
|
Using disability adjusted life years (DALYs), a composite measure incorporating premature mortality and years lived with disability, the Global Burden of Disease study developed a ranking of conditions contributing to disease burden around the world (1). Of the top 10 conditions, 5 were mental disorders, and of these, major depression ranked first. Overall, unipolar major depression ranked fourth as a cause of disease burden on a worldwide basis. In economically developed countries such as Canada, major depression ranked second. The impact of major depression was projected to increase in upcoming decades (1). Major depression is an important determinant of population health status for 3 reasons. First, it is extremely common. Recent Canadian estimates have placed the 12-month prevalence of major depression between 4% and 10%, consistently demonstrating that this is a highly prevalent disorder within the population (2–8). Second, major depression causes substantial disability, at a level that compares with other major medical conditions (9). In fact, impaired functioning is an intrinsic feature of the disorder, according to contemporary definitions (10). Third, major depression is an important cause of premature mortality. In particular, suicide (which ranks among the top 10 causes of mortality in Canada) is the fourth leading cause of potential years of life lost (PYLL) in Canada (11). PYLL due to 2 other prominent conditions—ischemic heart disease and accidents—is declining rapidly, whereas PYLL due to suicide is increasing (11). Declining PYLL for heart disease and accidents represent important success stories for public health in Canada. Public health progress against major depression must also be pursued energetically. On a clinical level, pharmacologic and nonpharmacologic strategies are available for treatment of this condition. Much attention has focused on these advances. A disturbing lack of evidence exists, however, with respect to the mental health of the population improving due to these clinical advances. This has recently attracted the attention of commentators in the field, one of whom has commented that antidepressants may be “overrated” (12). An example of a population-based approach to major depression may be found in a public health initiative in the US called “National Major Depression Screening Day.” This initiative targets several key aspects of the interface between the health care system and mood disorders in the community, using approaches based on public education, case-finding, and educating professionals (13). Many other population-based studies have incorporated similar principles but in different ways. Based on the idea that improved access to treatment and improved outcomes of treatment should impact favourably on population health, many studies have attempted to increase treatment utilization and to improve clinical outcomes, using methods such as professional education and disease management (14). In Canada, we hope that diminishing stigma, barrier-free access to health care services, and improved clinical care will accomplish these objectives, but previously we have lacked the ability to evaluate this. This paper’s objective is to report changes in major depression point prevalence over time, in treatment utilization, and in long-term antidepressant use. MethodsData from the National Population Health Survey (NPHS) were used in this analysis. The NPHS is a longitudinal study of a Canadian national sample. The original survey included 17 626 subjects sampled in 1994–1995, but additional provincial “buy-ins” resulted in a larger sample in 1996–1997. A third iteration of data collection occurred in 1998–1999. The NPHS employed a brief predictive instrument, designed to identify probable episodes of major depression in the year preceding the interview. Kessler and others developed the instrument called the Composite International Diagnostic Interview Short Form for Major Depression (CIDI-SFMD) (15). Validation studies suggest that the instrument is sensitive but somewhat nonspecific for major depressive episodes (MDEs) (16,17). The CIDI-SFMD provides a 12-month period prevalence estimate. Period prevalence refers to the proportion of the population meeting DSM-IV criteria for major depression at any time in the preceding year. Period prevalence is a problematic way of measuring prevalence, because it is not sensitive to the impact of treatment on population health. An individual who develops an MDE and then promptly seeks and receives effective treatment will be recorded in a period prevalence calculation in the same way as a person who does not seek treatment and remains ill. For this reason, an indicator of point prevalence was derived for this study by combining the CIDI-SFMD output with responses to a distress scale included in the NPHS interview. The distress scale comprised various CIDI items that inquired into feelings of sadness, nervousness, restlessness, hopelessness, worthlessness, and feelings that “everything was an effort” (18). Additional items clarified whether these symptoms occurred “a lot,” “somewhat,” “a little,” “more than usual,” “the same,” or “less than usual” in the preceding month. In this analysis, subjects with a CIDI-SFMD score indicating an 80% or greater chance of having had an MDE in the preceding year, combined with reporting distress at greater-than-usual levels in the preceding month, were regarded as a measure of point prevalence of major depression. The NPHS measured treatment utilization in various ways. Two questions were considered most pertinent to treatment utilization for major depression: one that referred to the use of antidepressants in the preceding month and another that asked about consultations with health professionals for purposes of emotional or mental health in the past year. In the current analysis, the proportion of subjects reporting antidepressant use, the proportion reporting that they consulted a professional about their emotional or mental health, and the proportion reporting both or either type of utilization were calculated.
|
||||||