Summary prepared by Sheldon Cohen in collaboration with the Psychosocial Working Group. Last revised October, 1998.

Chapter Contents:
a. Definition and Background
b. Measurement
c. Relation to SES
d. Relationship to Health
e. Limitations
f.  Conclusions
g. Selected Bibliography

Definition and Background

The gold standard for a research diagnosis of depression is the Structural Clinical Interview (SCID), a clinical interview that uses the DSM-III-R criteria for illness. However, because of the time and expense required to administer a clinical interview, epidemiologic type studies often use clinical interviews designed for administration by lay interviewers (Composite International Diagnostic Interview [CIDI] or the Diagnostic Interview Schedule [DIS]) or self-report questionnaires that measure symptoms and mood rather than illness and disorder. We will describe the SCID interview, as well as two of the most popular self-report measures, the Center for Epidemiological Study of Depression Scale (CES-D), and the Beck Depression Inventory (BDI). There are, however, a number of other self-report scales one might consider including the HRSD, the Zung, the MMPI-D scale, and the MAACL-D scale.

Measurement

The SCID is a semi-structured interview for making the major Axis I DSM-III-R diagnoses. It is administered by a clinician and includes an introductory overview followed by nine modules, seven of which represent the major axis I diagnostic classes. Because of its modular construction, it can by adapted for use in studies in which particular diagnoses (e.g., depression only) are of interest. The output of the SCID is recorded as the presence or absence of each of the disorders being considered, for current episode (past month) and for lifetime occurrence. The reader is referred to Spitzer et al. (1992) and Williams et al. (1992) for more detailed information about the interview and its psychometrics.

The Composite International Diagnostic Interview (CIDI) is a structured diagnostic interview designed to be used by trained interviewers who are not clinicians (Kessler et al., 1994). The interview can be modified to include only the stem measures for major depression.

The Beck Depression Inventory (BDI) is a list of 21 symptoms and attitudes that are each rated in intensity. Examples include: mood, pessimism, sense of failure, lack of satisfaction, guilt feelings, self-dislike, etc. It is scored by summing the ratings given to the 21 items. Although originally designed to be administered by trained interviewers, it is most often self-administered and takes 5-10 minutes. This instrument has been used to measure severity of depression in depressed samples but has also been used to assess depression in general population samples. It is also associated with other self-report measures of depression. The reader is referred to Beck, Steer & Garbin (1988) for an overview of the measure and its applications.

The Center for Epidemiologic Studies of Depression Scale (CES-D) was designed to measure current level of depressive symptomatology, and especially depressive affect. The 20 items were chosen (from 5 previously used depression scales) to represent all major components of depressive symptomatology. These include: depressed mood, feelings of guilt and worthlessness, feelings of helplessness and hopelessness, loss of appetite, sleep disturbance, and psychomotor retardation. Each item is rated on 4-point scales indicating the degree of their occurrence during the last week. The scales range from "rarely or none of the time" to "most all of the time." The scale can distinguish between clinical groups and general community groups. Although it is usually scored continuously, there are various cutoff scores for clinical depression with reasonable associations between cutoff scores and a clinical diagnosis. The reader is referred to Insel (1986) for an excellent overview of the CES-D including suggestions for cutoff scores.

Relationship to SES

In general, depression is thought to be associated with SES in the expected manner. For example, the BDI has been found to be inversely related to educational attainment in a sample of unselected adults (r=-.34) and in middle aged women (Matthews et al., 1989). See Beck, Steer & Garbin (1988) for a review of demographics and the BDI.

The CES-D has also shown correlations with SES. Comstock & Helsing (1976) report associations, with very nice gradients for employment and household income. Ensel (1986) reports graded relations between both education and income in a large community sample.

In regard to the SCID, household income has been associated with depression in a sample of Caucasian twins and their parents, although the gradient was not very clear (Meyer et al., 1996). On the other hand, data from the National Comorbidity Study showed a nice gradient for education, and a relation with income driven mostly by a very high risk in the lowest income category (Blazer et al., 1994).

Relationship to Health

Depression is a health outcome. However, depression has been associated with many physical health outcomes including reporting symptoms, utilization of health services, and morbidity and mortality.

Limitations

The use of various cut-offs on the self-report measures provide only screening type estimates of clinical depression with both inclusion and exclusion errors. The self-report scales may also be biased toward diagnosing more depression in women than men because some of the items reflect the kind of feelings and behaviors more likely to occur in women (e.g., crying). The SCID is the gold standard but time consuming and expensive to implement.

Network Usage

The network sees the measurement of depressive symptoms, and depression histories, as critical in the effort to disentangle the SES---Health pathway. Depression measures have been included in a variety of Network sponsored research, including the CARDIA Year-15 exam, and other smaller scale studies.

Conclusions

The choice of an instrument to assess depression is largely subject to the design of the study and available resources. The SCID is the gold standard for measurement, but requires subject time and trained clinical interviewers. Shorter interviews requiring less training (like the DIS) are the second choice. However, most epidemiologic type studies do not allow for either interview approach. In these cases, self-reported depression questionnaires like the CES-D and Beck are acceptable. Irrespective of the type of measurement, depression is generally found to increase with decreases in SES. A clearer understanding of how SES would trigger depression is needed.

Selected Bibliography

Beck, A. T., Steer, R. A., & Garbin, M. G. (1988). Psychometric properties of the Beck Depression Inventory: Twenty-five years of evaluation. Clinical Psychology Review, 8, 77-100.

Blazer, D. G. et al. (1994). The prevalence and distribution of major depression in a national community sample: The national comorbidity survey. American Journal of Psychiatry, 151, 979-986.

Comstock, G. W., & Helsing, K. J. (1976). Symptoms of depression in two communities. Psychological Medicine, 6, 551-563.

Ensel, W. M. (1986). Measuring depression: The CES-D scale. In N. Lin, A. Dean & W. Ensel (Eds.), Social support, life events, and depression. New York: Academic Press.

Kessler, R. C., McGonagle, K. A., Zhao, S., Nelson, C. B., Hughes, M., Eshleman, S., Witchen, H.-U., & Kendler, K. S. (1994). Lifetime and 12-month prevalence of DSM-III-R psychiatric disorders in the United States: Results from the National Comorbidity Survey. Archives of General Psychiatry, 51, 8-19.

Matthews, K. A. et al. (1989). Educational attainment and behavioral and biologic risk factors for coronary heart disease in middle-aged women. American Journal of Epidemiology, 129, 1132-114?.

Meyer, J. M. et al. (1996). The Virginia twin-family study of adolescent behavioral development: Assessing sample biases in demographic correlates of psychopathology. Psychological Medicine, 26, 1119-1133.

Spitzer, R. L. et al. (1992). The structured clinical interview for DSM-III-R (SCID). I: History, rationale, and description. Archives of General Psychiatry, 49, 624-629.

Williams, J. B. W. et al. (1992). The structured clinical interview for DSM-III-R (SCID). II. Multisite test-retest reliability. Archives of General Psychiatry, 49, 630-.