Depression is a mood disorder characterized by states of sadness and feelings of worthlessness or emptiness and accompanied by physical symptoms such as decreased activity, poor appetite, and poor sleep serious enough to impair functioning in social, occupational, educational, or other situations [1]. The current definition of a major depressive episode (MDE) is based on one of two classifications [2]: DSM-5 [3] and ICD-10 [4]. The DSM-5 includes additional criteria to define major depressive disorder (MDD) (see Additional file 1). The DSM-5 allows for a specifier for depressive episodes that have their onset in pregnancy or within 4 weeks postpartum, collectively termed major depressive episodes, with peripartum onset. Of note, a woman can still meet criteria for depression in pregnancy or postpartum even if the onset did not occur within the “peripartum onset” time frame. In clinical practice and research, depression occurring up to 1 year postpartum is generally considered “postpartum depression” [5].
General adult population
Prevalence
Depression is the most common cause of disability worldwide, with over 300 million people now living with depression, an increase of more than 18% between 2005 and 2015 [6]. Estimates of prevalence for depression vary by characteristics such as age and sex. For example, women are more likely to suffer from major depressive disorders than men [7, 8]. Many studies report depression rates based on results from self-reported screening questionnaires, rather than validated diagnostic interviews, but this is known to exaggerate rates substantially and to blur distinctions between low- and high-prevalence groups [9]. The 2012 Canadian Community Health Survey-Mental Health used the diagnostic interview technique among 25,113 individuals and reported annual prevalence for major depressive disorder (MDD) of 3.9% (95% CI 3.5–4.2%) and lifetime prevalence of 9.9% (95% CI 9.3–10.5%) [10]. It also reported an annual and lifetime prevalence of MDE among Canadians at 4.7% and 11.3%, respectively [10]. Another 2012 Canadian national health survey reported the highest rate of a MDE was among 15–24-year-olds, with 7% having had depression in the past year, compared to 5% in people aged 25–64 years, and 2% in those 65 years and older [11].
Risk factors
There are several risk factors that have been associated with depression in adults. Socio-demographic risk factors include sex, age, marital status, low socioeconomic status, and low education level [8, 12,13,14]. In Canada, the largest difference between sexes is in the 15–24 age range, with the difference diminishing and nearly disappearing at more advanced ages [15]. Additionally, married and never-married individuals experience less depression than those who are separated, divorced, and widowed [8]. Other factors such as trauma early in life (e.g. neglect or sexual abuse), chronic disease (e.g. cancer, cardiovascular disease), previous history of depression, and a family history of depression have also been linked to depression [8, 16, 17].
Consequence of depression
Depression affects a person’s physical health and well-being and impacts psychosocial functioning (e.g. personal relationships, employment). A review by Evans et al. [18] conclude that there may be a bidirectional link between depression and disease, as depression might be an etiologic factor for new disease (e.g. stroke) and also might affect the course of existing chronic diseases such as diabetes mellitus. Depression can affect work performance through absenteeism and presenteeism (decreased work productivity while at work), which is a large cost to employers in terms of productivity [2]. In addition, many depressed individuals are unable to enter the workforce. On a population level, it also has a large societal impact through increased health service utilization, decreased work productivity, increased burden on family members, and increased resource costs related to disability [19]. In the 2003 Canadian Community Health Survey, the total economic burden of mental illness (including health service utilization, long- and short-term work loss, and health-related quality of life) was said to be $51 billion dollars [19]. More recently, direct healthcare costs associated with MDD were determined using a population-based cohort study in Ontario, Canada. The age- and sex-adjusted annual per-capita cost among those with MDD was higher than the comparison group (those without MDD or psychological distress) [$3914 (95%CI $2943–4888) vs $3206 (95%CI $2820–3591)], and the population-wide excess cost for those with MDD was $256 million (prices converted to CDN $ from reported USD) [20].
Although effective interventions to reduce the effects of depression exist, individuals need to be identified to benefit from these interventions. The Mental Health Commission of Canada reports that almost half of those who feel they have suffered from depression or anxiety have not seen a doctor about this problem [21]. In addition, among those who have been diagnosed accurately, many do not receive minimally adequate treatment [21, 22].
Current recommendations
In 2013, the Canadian Task Force on Preventive Health Care (CTFPHC) recommended to not routinely screen for depression (this was based on very-low-quality evidence; see Additional file 2). There is disagreement in recommendations between Canada, the USA, and the UK. Neither the CTFPHC nor the United Kingdom National Screening Committee (UKNSC) recommended screening, whereas the US Preventive Services Task Force (USPFTF) recommended screening based on prioritization of linked evidence of effective follow-up and treatment of screen-identified individuals. Additional file 2 provides additional on how the USPSTF recommendation differs from Canada and the UK, followed by some speculation as to why [23].
Pregnant and postpartum population
Prevalence
Although estimates of the prevalence of major depression should be based on validated diagnostic interviews, many studies report depression rates based on results from self-reported symptom questionnaires and other non-valid methods [9]. An Agency for Healthcare Research and Quality SR reported that the period prevalence of major depression during pregnancy (conception to birth) was 12.7% (95%CI 7.1–20.4%) [24]. However, this is based on one primary study. The period prevalence from birth to 3 months postpartum was 7.1% (4.1–11.7%) [24]. A recent US study in which women were interviewed, and diagnosis made using the DSM-IV criteria, found the 12-month period prevalence of MDD to be 8.4% among women who were currently pregnant or had been pregnant in the past 12 months, 9.3% among postpartum women, and 8.1% among non-pregnant women [25]. It should be noted that the prevalence for postpartum women could include time in which they were pregnant, as it covers the previous 12 months.
Risk factors
There are many risk factors for depression during pregnancy, including younger age, a history of depression, exposure to domestic violence, increased life stressors, a lack of social support, unintended pregnancy, lower income, lower education, smoking, single status, and poor relationship quality [26, 27]. Prior depression is the greatest risk factor for postpartum depression. Nevertheless, for women who experience postpartum depression, it is a first episode among 40% [28]. Other postpartum risk factors include untreated depression or anxiety during pregnancy, experiencing a stressful life event during pregnancy, having a traumatic birth experience, preterm birth or infant admission to neonatal intensive care, low levels of social or partner support, experiencing domestic violence, low socioeconomic status, obstetric complications, low birth weight, and breastfeeding problems [27].
Consequence of pregnancy and/or postpartum depression
While the prevalence of depression in women during pregnancy and the first year postpartum may be similar to that for other women [24], depression has specific negative short- and long-term effects on maternal health, child health and development, and on the overall health of families [29]. Depression during pregnancy is associated with unhealthy behaviours including poor self-care, poor nutrition, increased use of tobacco and alcohol, lower prenatal care seeking, and poorer maternal-fetal bonding [30, 31]. Postpartum depression may lead to difficulties with infant care, a decrease in breastfeeding initiation, and poor-quality mother-child interactions including mutual touching, smiling, and vocalizations, and compromised mother-child bonding [30, 32, 33]. Negative outcomes for infants in mothers with prenatal and postpartum depression may also include preterm delivery, lower birth weight, cognitive, emotional, social, neural functioning or developmental delay [34,35,36,37].
Almost half of Canadians with depression have not seen a primary care provider about their depression [38]; for depression in pregnancy and postpartum, the number may be even higher [35]. Screening for depression, if effective, would allow for treatment among women who would not otherwise be identified and possibly lessen the negative impacts to the mother, fetus/infant, and family. Several treatment options exist, including psychosocial strategies (e.g. peer support, non-directive counselling and self-care such as exercise), psychological therapies, and antidepressant medications [36, 37]. The last poses the additional challenge of considering the safety of exposure to psychotropic medications to the baby in utero and through breast milk [39].
Current practice and recommendations
Across Canada, there is a lack of consensus on how and when prenatal and postpartum depression screening should occur with different provinces and territories having different approaches. Additional file 2 provides examples on how the provinces of Ontario, British Columbia, Alberta, Nova Scotia, and the territory of Nunavut screen women during pregnancy and postpartum. There is discordance in recommendations between Canada, the USA, and the UK. Neither the CTFPHC or UKNSC recommended screening in contrast to the USPFTF recommendation for screening on results that combined screening with treatment. Additional file 2 provides additional details on why the USPSTF recommendation may differ from Canada and the UK [23].
Definition of a controlled trial of screening intervention
The intent of a screening programme for depression would be to identify symptomatic disease that would not otherwise be identified or reported (i.e., by spontaneous patient self-report or clinical inquiry). Current approaches for depression screening are based on the use of questionnaires (e.g. Edinburgh Postnatal Depression Scale (EPDS), Patient Health Questionnaire (PHQ-9), Beck Depression Inventory) to identify people who may have undetected depression. If effective, screening for depression could reduce the health burden in those who otherwise would not be identified [23].
The following three eligibility criteria have been used when considering depression screening trials [40]: (i) the patient population must be clearly defined and participants randomized prior to administering the screening test; (ii) patients who are known to have a current episode of depression or are already being treated for depression close to the time of eligibility assessment are excluded, as screening is intended to identify undetected cases and those who are known to have depression would not be screened in actual clinical practice; and (iii) similar depression management and treatment resources must be provided to patients in the screening arm of the trial and patients in the non-screening arm of the trial who are identified as depressed via other methods (e.g. unaided clinician diagnosis, patient report).
Objective
The CTFPHC is undertaking a systematic evaluation of the evidence to inform its guideline recommendations for depression screening during pregnancy and up to 1 year postpartum in primary health care settings in Canada and to provide an updated recommendation for the general adult population. This protocol outlines the methodological process for performing these two systematic reviews (SR) of the evidence on the benefits and harms of screening for depression. This protocol updates the 2013 McMaster Evidence Review and Synthesis Centre (ERSC) SR previously used by the CTFPHC [41] for their guideline recommendation on depression screening in adults [42], where the pregnant and postpartum population was considered as a subgroup of the general adult population. The scope of the forthcoming guideline has been revised to more formally consider women during pregnancy and postpartum. The analytic framework depicts the structure used to address the key questions for evaluating the benefits and harms of depression screening (see Figs. 1 and 2). We will use the following key questions to guide the SRs.
General adult population
Key question 1
What are the benefits and harms of screening versus no screening for depression in the general adult population in primary care or other non-mental health clinic settings?
Key question 1a
What are the benefits and harms of screening versus no screening for depression in the general adult population in primary care or other non-mental health clinic settings for patients targeted because they have characteristics that may suggest an elevated risk of depression? (characteristics as defined in primary studies, not including exclusion criteria).
Pregnant and postpartum population
Key question 1
What are the benefits and harms of screening versus no screening for depression during pregnancy and up to 1 year postpartum in primary care or other non-mental health clinic settings?
Key question 1a
What are the benefits and harms of screening versus no screening for depression during pregnancy and up to 1 year postpartum in primary care or other non-mental health clinic settings for patients targeted because they have characteristics that may suggest an elevated risk of depression? (characteristics as defined in primary studies, not including exclusion criteria (e.g. previous depression in pregnancy or postpartum)).
This systematic review is being conducted to inform a guideline on screening for depression. We will conduct a separate systematic review on additional key questions about patient values and preferences should the working group decide it is needed to inform the guideline. For each population, after reviewing the evidence from KQ1 and KQ1a, if the working group believes that SR information on patient values and preferences would potentially change recommendations beyond what is learned about values and preferences identified from focus groups conducted by the Knowledge Translation Team of St. Michaels Hospital in Toronto, Ontario [43], supporting the development of recommendations for this guideline, then we will move forward with this additional review(s). The potential key questions are:
Key question 2
How do patients value outcomes that may occur from screening for depression in the general adult population and how do these values influence decisions about being screened?
Key question 2a
How do patients with characteristics that may suggest an elevated risk of depression value outcomes that may occur from screening for depression in the general adult population and how do these values influence decisions about being screened? (characteristics as defined in primary studies, not including exclusion criteria).
The same key questions on patient values and preferences may be addressed in the pregnant and postpartum population. The decision to proceed or not proceed in one population does not determine whether patient values and preferences will be undertaken for the other population. If we do pursue a SR on KQ2 and KQ2a, a separate protocol will be developed at that time. This would include topic refinement and all relevant Population, Intervention, Comparator, Outcome (PICO) criteria and methods.
