Chapter Overview
Depression is a common problem that carries a high burden of suffering, which can include death from suicide. Effective treatment is available. However, in 1990 as in 1979 the Task Force recommended that routine screening for depression in asymptomatic individuals be excluded from periodic health assessments based on fair evidence that such screening by questionnaire did not improve detection rate or management.<1,2> However, physicians should be sensitive to the possibility of depression in their patients, particularly those at higher risk.

Burden of Suffering
Depression is frequently encountered in family practice and in ambulatory care settings. The lifetime prevalence of clinically significant depression is 15% to 30%; it is about twice as common among women as among men. The prevalence in the general population ranges between 3.5% and 27% depending on the definition used and the population studied; however, it is thought to have increased among children and adolescents. People who are single, divorced, separated, seriously ill, recently bereaved or those with a family history of depression have a greater incidence than others. Depressed individuals frequently present with physical symptoms, which may make diagnosis more difficult, particularly in the early stages and in mild cases. Important episodes of depression have been overlooked, so that instead of recognizing and treating the problem diagnostic testing or treatment for other illnesses is performed. Depression has a significant effect on the patient’s quality of life and productivity, but psychiatric referral also has some negative implications regarding societal attitudes.

Spontaneous remission can occur over 6 to 12 months in up to50% of affected people; however, about 50% of those who suffer from major depression become chronically depressed. Affected people are more likely than others to be suicidal: 30% to 70% of people who have committed suicide were previously identified as having major depression. In Canada, in 1986, suicide accounted for an estimated97, 600 potential years of life lost among men and another 25,300years among women.

Maneuver
The gold standard for diagnosing depression is careful application of standardized clinical criteria. In the primary care setting the problem must be recognized first and then properly evaluated. Several short (12-38 item), self-administered questionnaires have been proposed to assist with early recognition. When evaluated, these questionnaires have been generally sensitive to changes in clinical status but correlation with other tests or with clinical assessment has ranged from 0.40 to 0.89, with sensitivity 64-91% and specificity 56-82%.Hence, for many instruments, validity has not been fully established.

Effectiveness of Early Detection and Treatment
Once identified, depression can be treated effectively with medication and psychotherapy; however, there is no conclusive evidence that treatment in the early stages of depression has greater long-term effects than intervention started later in the course of the illness.

Four randomized controlled trials have evaluated whether routine use of a screening questionnaire provided any benefit in terms of detection and management of depression. Shapiro and associates asked 1,242 patients attending an inner-city primary care teaching facility to complete the General Health Questionnaire (GHQ) before seeing a physician.<3> The provision of the GHQ information to the physician had no statistically significant effect on the detection of psychologic problems except among patients over 65 years of age. There was no ultimate effect on patient management, even in the group over 65 years of age.

Hoeper and collaborators found that physicians’ knowledge of a "positive" GHQ result had no effect on the detection of psychologic distress among 1,469 patients in a Wisconsin primary care office.<4>

Using somewhat weaker methods in terms of identification of case and control subjects and choice of outcome measures, Johnstone and Goldberg used the GHQ to assess 1,093 patients.<5> New episodes of psychiatric illness were diagnosed and treated in 16% ofthe patients without data from the GHQ; an additional 11% were identified for treatment after the GHQ results were reviewed.

Zung and colleagues found that physicians informed of positive scores of the Zung Self-Rating Depression Scale detected depression in more patients (68% of 102) than when they were not informed of the results (15% of 41).<6> However, there were significant flaws in the design and execution of this study, particularly in terms of losses to follow-up.

In a well designed, randomized controlled trial, Magruder-Habiband coworkers used the Zung Self-Rating Depression Scale and a DSM-III screen to evaluate depression status in a group of subjects over age 45 attending a U.S. Veterans’ Administration general medical clinic over a 12 month period.<7> Providing physicians with scores for patients whose depression was unrecognized in the clinical setting had an important impact on eventual recognition and management. However, in order to reduce the number of false positives, only patients scoring positive on both self-rating scale and a research assistant administered DSM-III checklist were identified to the attending physician. Hence, while the self-assessment instrument maybe feasible in a primary care setting, the study does not evaluate the effectiveness or the impact of this instrument alone on the recognition and management of depression. The study did, however, provide valuable insight into the impact of informing physicians about unrecognized depression, and in conjunction with the Shapiro study indicates that further studies would be of value.

Recommendations of Others
The U.S. Preventive Services Task Force does not recommend routine screening but encourages physicians to have a high level of clinical suspicion.<8>

Conclusions and Recommendations
Overall, these five trials fail to provide adequate evidence to support the use of routine screening tests for the early detection of depression. In fact, the current evidence supports not routinely using screening instruments but rather to maintain a high level of clinical sensitivity.

Unanswered Questions (Research Agenda)
The following have been identified as research priorities:

1. Conducting research into improved methods of identifying people at high risk for depression and developing a simple diagnostic test for use in this group by primary caregivers.
2. Evaluating the impact of questionnaires in the early detection of depression and subsequent management of patients over 65 years of age.

This review was initiated in November 1992 and updates a report published in May 1990.<1> Recommendations were finalized in January 1994.

Acknowledgements
The original Task Force report was co-authored by Dr. Graham Worrall, MSc, DRCOG, MRCGP, CCFP, visiting lecturer, Community Medicine, Memorial University, St. John’s, Newfoundland.

Full Citation
Feightner JW. Early detection of depression. In: Canadian Task Force on the Periodic Health Examination. Canadian Guide to Clinical Preventive Health Care. Ottawa: Health Canada, 1994;450-4.