Screening for depression: the global mental health context

Depression is the leading mental health related cause of the Global Burden of Disease. The sequelae of depression contribute further to its immense public health burden, including impact of maternal depression on child growth and development, and increased risk for dementia, suicide, and premature mortality from co‐occurring physical disorders. The World Health Organization (WHO)'s Mental Health Gap Action Programme (mhGAP) guidelines recommend antidepressant medication or brief psychological treatments for moderate to severe depression, and there is a mounting body of evidence from trials on how these treatments can be delivered in real‐world primary care settings in low resource contexts by relying on lay health workers and primary care practitioners1.

Despite this evidence on cost‐effective and scalable models of depression care, the vast majority of people suffering from this condition – for example up to 90% in India and China – do not receive treatment. A major barrier to receiving treatment is the low detection rate in primary care. To date, virtually all efforts to improve detection have focused on training of general practitioners, and this is also the approach adopted by the mhGAP guidelines. Yet, the evidence in support of training is weak. In an early WHO Collaborative Study, following training of primary care workers in four countries (Colombia, India, Sudan and Philippines) to detect mental disorders, detection rates barely increased from 2.4% to 2.6%2. In a Kenyan study, detection rates post‐training did not significantly differ between the trained and the control group3. In a cluster randomized controlled trial conducted in Malawi, while there was a significant difference between the 5‐day mental health trained primary care workers and workers in the control condition, the training arm failed to detect 90% of patients with depression4. In short, training alone has a negligible or, at best, a small impact on detection rates.

It is in this context that screening should be considered as a cost‐effective supplementary strategy to improve the detection of depression in routine care settings and translate the evidence of effective interventions to reduce its global health burden. Many of the trials in low and middle income countries, as well as US‐based studies such as IMPACT5 and PROSPECT6, have shown that lay workers or general medical ancillary personnel (e.g., nurses and social workers) can be taught to screen for depression and other common mental disorders effectively using brief questionnaires with a high degree of acceptability.

We emphasize that the use of such questionnaires also meets the criteria recommended for screening tests, for example, that the test is valid, feasible at a very low resource cost, and that there are cost‐effective interventions to follow. Additionally, screening using symptom measures avoids the complexity of diagnosis, and the same measure can be used for monitoring of clinical progress and outcomes, as in the Improving Access to Psychological Treatments national program in England7. Based on these experiences, and the recent recommendations of the US Preventive Services Task Force8, we propose steps regarding the implementation of screening for depression in routine care.

The first consideration is what measure should be used for screening for depression. Experience supports the use of brief, self‐report questionnaires, such as the Patient Health Questionnaire (PHQ‐9)9, which has been widely used internationally, takes a few minutes to complete, can be used to generate a diagnostic outcome, and shows sensitivity to treatment response. One caveat, however, is that, because depression and anxiety frequently co‐exist, additional brief screening for anxiety may also be appropriate, using such measures as the Generalized Anxiety Disorder 7 (GAD‐7)10.

The second consideration is how screening should be done. These questionnaires can be delivered either in self‐report or health worker delivered formats and, with the growing use of digital technologies, can also be used on devices to allow for self‐screening and remote monitoring of clinical progress. Stepped approaches to screening, for example using the two‐item version of the PHQ routinely for all attenders, followed by the remaining seven items for those who screen positive on at least one question, may also be a cost‐effective approach.

The third consideration is who should be screened. Given the high prevalence of depression and other common mental disorders in primary care populations, one option is to routinely screen all adult attenders. However, this may not be feasible in the very low resource settings, where the possible yield of cases may greatly exceed the feasibility of delivering effective interventions. This challenge may be partly addressed by calibrating the screening questionnaire cut‐point to a higher level, so that only more severe presentations are identified. An alternative approach is to screen high‐risk or vulnerable groups such as mothers with newborn children, people with chronic diseases, people with chronic sleep disturbances or medically unexplained somatic complaints or severe social stressors.

The fourth consideration is when screening should take place. Since depression is frequently a recurring condition, annual screening, in particular for individuals with a prior history, would seem sensible.

In conclusion, now that we have strong evidence on how we can effectively treat patients with depression in a cost‐effective way using locally available resources, it is time to scale up this evidence through addressing the barrier of low detection rates by instituting routine screening. This recommendation to improve detection needs to be accompanied by a research agenda addressing many of the considerations outlined above regarding the implementation of screening, such as the measure to be used, the frequency, the method of delivery and the target group.

Routine screening for depression in adult primary care attenders is a vital milestone in the journey towards reducing the very large treatment gaps globally and scaling up the robust evidence on cost‐effective interventions for this common mental disorder.

Charles F. Reynolds 3rd1, Vikram Patel2
1University of Pittsburgh School of Medicine and Graduate School of Public Health, Pittsburgh, PA, USA; 2Department of Global Health and Social Medicine, Harvard Medical School, Boston, MA, USA; Center for Chronic Conditions and Injuries, Public Health Foundation of India, New Delhi, India

The authors are supported by the US National Institute of Mental Health (grants nos. MH P30 90333 and R34 MH 96997), the Wellcome Trust, and the Brain and Behavior Research Foundation.