In 1994 the Canadian Task Force on Preventive Health Care addressed screening for depression in asymptomatic individuals during periodic health assessments.1 On the basis of a review of the literature published to May 1993, the task force concluded that there was fair evidence to exclude screening for depression in the primary care setting (grade D recommendation), because screening instruments did not improve the detection rate or management of depression, particularly among people at high risk, such as those with a family history of depression. The task force recently revisited the topic to determine whether studies published in the past 10 years provided new evidence to recommend that primary care practitioners routinely screen their patients for depression.
In 2002 a systematic review was conducted at the request of the US Preventive Services Task Force to determine whether routine screening improves the detection, treatment and outcome of depression.2,3 This rigorous overview provided the basis for our review to update the Canadian task force's recommendation (Table 1). (A summary of the methods and results of the Canadian task force's review of the US task force's work, the subsequent literature update and the process of arriving at the practice recommendations are available at www.ctfphc.org.)
Depression is frequently encountered in patients in the primary care setting. The 1994/95 National Population Health Survey, a Canadian longitudinal study that included household residents in all provinces, gave a 1-year prevalence rate for major depressive disorder of about 6% among Canadians 18 years of age and older.8 Rates were higher among females than among males and declined in both sexes in the elderly population. Data from a province-wide Canadian community-based survey revealed a 6-month prevalence of depression of 5.9% among children 6–16 years of age.9 Certain subgroups of the Canadian population may be at increased risk for depression. The 2000/01 Canadian Community Health Survey showed that, after controlling for socioeconomic factors, Aboriginal people living off-reserve were 1.5 times more likely than non-Aboriginal people to have experienced an episode of depression in the previous year.10
The prevalence of major depression in Canadian primary care settings is unknown; however, in the United States point prevalence estimates of between 4.8% and 8.6% have been reported.2,11
When making its recommendations (Table 1), the Canadian task force not only considered the effectiveness of screening tools in identifying patients with depression in primary care settings, but it also evaluated the treatment options and outcomes arising from the initial screening process, weighing at each point the potential benefits of intervention against the potential harms (including false-positive results leading to further, unnecessary diagnostic investigation). The systematic review for the US task force2 found good evidence that screening for depression in the primary care setting improves detection rates. Furthermore, when screening is linked to appropriate follow-up and treatment, the overall result, based on a meta-analysis of findings from key studies, was a reduced risk of depression. However, when identification of depressed patients was not linked to follow-up and treatment, there was generally much less improvement in depressive symptoms. Evidence regarding screening adolescents and children is lacking. The available evidence led the US task force to recommend that adults be screened for depression “in clinical practices that have systems in place to assure accurate diagnosis, effective treatment, and follow-up” (grade B recommendation).12 The Canadian task force, after reviewing this body of evidence in the Canadian context, and having ascertained that no new evidence was available, reached the same conclusion (Table 1).
In the studies reviewed, “effective follow-up and treatment” referred to screening programs that were integrated with both feedback to the clinician regarding depression status and a system for managing treatment (antidepressants and psychotherapeutic interventions). Trials that included access to case management or mental health care as part of the system of care were particularly effective in reducing depressive symptoms.