Depression is very common in all health-care settings, and primary care is no exception. Recently, our group undertook a meta-analysis in order to better understand the issue of diagnostic error in depression. We identified a surprisingly large number of primary studies—157, across 11 countries—that examined the ability of clinicians to diagnose a mental disorder.

We found that depression was identified accurately in about half of true cases. Clinicians correctly reassured eight of 10 healthy people but with substantial false alarms. In a typical urban practice (where the prevalence of depression is 20%), the error rate was 25% (10% missed cases and 15% false alarms).

Several factors influenced the clinical judgments of primary-care providers.

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  • International differences existed: Primary-care practitioners in Italy and the Netherlands were most successful in their diagnoses; those in the United States, the United Kingdom, and Australia were least successful. Health-care differences in each country are likely influencing the ability of clinicians to identify depression.
  • Diagnostic accuracy was significantly greater in younger adults than in older adults. Clinicians struggled to recognize depression in older people even after adjusting for differences in prevalence.
  • One of the most important factors influencing detection is whether distress and depression are discussed at the appointment. Examining the patient prospectively over an extended period rather than in a one-time assessment improved the accuracy of depression diagnosis. In a second assessment, the patient is more likely to discuss sensitive issues and offer extra information that can aid the diagnosis, and the practitioner has additional time to observe clinical change and employ screening instruments. We therefore recommend scheduling second appointments for people with unclear diagnoses.
  • We found that detection of mild depression (and distress) was inferior to the detection of more severe conditions. The detection of mild disorders is challenging because symptoms do not differ greatly from those seen in healthy but stressed individuals, causing clinicians to underestimate the degree of the patient’s depression. Furthermore, in many cases, clinicians recognize symptoms but do not believe psychological issues are clinically significant.

Depression can be difficult for any health professional to identify. Few can remember the official diagnostic criteria, and a variety of occupational, financial, and life events (stressors) must be considered when trying to pinpoint the patient’s problem. As Zimmerman and colleagues noted in the journal Psychological Medicine, several groups are trying to develop simpler diagnostic criteria for major depression that would include only low mood, loss of interest or pleasure, guilt/worthlessness, impaired concentration/indecision, and suicidal thoughts.

We conclude that depression is common but underdetected and undertreated in primary care. However, accurate diagnosis is difficult based on existing criteria, and primary-care clinicians appear to perform no worse than other medical colleagues. Our results should not be interpreted as a criticism of clinicians’ skills but rather as a call for greater understanding of the predictors of diagnostic error as well as the interventions that may improve identification.

Alex J. Mitchell, MD is a psychiatry consultant at Leicester General Hospital, Leicester, UK.