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Construct Overview of Depression

Please note that this section is an archive and is no longer being updated.

Background

The widespread physical and social implications of depression and depressive symptoms continue to burden society. Depression was ranked as the fourth leading cause of disease burden worldwide by the World Health Organization (WHO) in 1996.¹ Researchers have projected that depression will be the second leading cause of disease burden by 2020. Depression is associated with increases in bed days of care, suicide rates, and medical care utilization, among others.¹

Depression is considered a syndrome, or complex of symptoms, which make up the individual criteria set forth by the Diagnostic and Statistical Manual of Mental Disorders (DSM).² Depressive symptoms take several diagnosable forms, including Major Depressive Disorder, Dysthymic Disorder, Bipolar Disorder, Cyclothymic Disorder, Mood disorder due to a general medical condition, and Substance-induced mood disorder. As an example, Major Depressive Disorder is characterized by loss of interest or pleasure in usual activities, change in appetite or weight, sleep disturbances, psychomotor disturbances, loss of energy, feelings of guilt or worthlessness, problems with concentration, and suicidal ideation. For diagnostic criteria specific to each of these disorders, please consult the DSM.

VA Relevance

Older VA patients who have the highest quartile depressive symptoms have 50% greater medical costs than those with lowest quartile symptoms.³ Depression and depressive symptoms are associated with decreased productivity and quality of life and increased mortality, morbidity, and costs.³ In 2002, the prevalence of Major Depression, Dysthymia, or depressive symptoms was 12% among VA inpatients and outpatients. The VA Technology Assessment Program (VATAP) provided a brief report on outcomes measurement in depression that summarized research with veterans. Some of the points were:

• Prevalence for depression among 2160 Boston male VA outpatients was 29%. (Hankin 1999)
• Based on findings from the National Registry for Depression, 54% of depressed veterans had an additional psychiatric diagnosis. PTSD and substance abuse were the most common comorbid psychiatric conditions. 88% of depressed veterans had comorbid medical conditions, with hypertension and arthritis being the most common. (Blow 2002)

Measurement

Measurement of depression is accomplished via interviews and self-report instruments. Interviews and instruments may be used to either diagnose or screen for depressive disorders or symptoms. Depressive disorders are commonly diagnosed using the criteria set-forth by the DSM and related structured or semi-structured interview protocols (i.e. the Structured Clinical Interview for DSM-IV-TR or SCID).

Screening instruments must be sensitive enough to detect Major Depression and have adequate positive predictive value to ensure that a substantial amount of patients who screen positive for depression would actually be diagnosed as such.¹ Because of their potentially high rate of use, screening instruments should be cost-effective, brief, and easy to administer.

Assessment of depressive symptomatology is challenging due to the blurry and often imperceptible lines between Major Depressive Disorder, Dysthymia Disorder, and normal depressed mood, or the "blues."⁴ In addition, depressive symptoms vary greatly among individuals, so instruments must tap into several different dimensions. These dimensions will vary based on the developers' underlying theory about the etiology of depression.⁴ Depressive symptoms also often overlap and co-occur with symptoms that define other disorders; for example, there is sometimes a difficult distinction between depression and anxiety. Lastly, in addition to the subjective bias inherent in self-report, other patient attributes may complicate the measurement of depression, such as lack of ability to communicate appropriately if severely depressed, cognitive deficits, and lack of motivation to respond at all.⁴

Through literature review, METRIC identified three commonly used self-report or interviewer-administered depression instruments and ranked them according to number of citations, as determined by the ISI Web of Knowledge.⁵ What follows is a brief summary of each instrument and three applicable references.

Most Frequently Cited Instruments

1. Beck Depression Inventory (BDI)
   [2545 Citations]
2. Center for Epidemiological Studies-Depression Scale (CESD)
   [286 Citations]
3. Geriatric Depression Scale (GDS)
   [159 Citations]

1. Maruish ME. 2000. Handbook of Psychological Assessment in Primary Care Settings. Lawrence Erlbaum Associates, Inc.: NJ
2. American Psychiatric Association. 1994. Diagnostic and Statistical Manual of Mental Disorders (DSM IV).
3. VA Technology Assessment Program (VATAP). 2004. Outcomes Measurement in VHA Mental Health Services: Outcomes Measurement in Depression (Short Report). Accessed July 2005. Available: http://www.va.gov/vatap/pubs/Bariatricfinalreport3-05.pdf
4. McDowell I and Newell C. 1996. Measuring Health: A Guide to Rating Scales and Questionnaires, Second Edition. Oxford University Press: NY.
5. ISI Web of Knowledge, Accessed June 2005. Available: http://isi01.isiknowledge.com/portal.cgi/wos/.