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Relationships of the dexamethasone suppression test to clinical severity and degree of melancholia
Abstract:
Investigators continue to debate whether the Dexamethasone Suppression Test (DST) reflects clinical severity or degree of melancholia ("endogeneity"). To evaluate this question, we studied 73 drug-free inpatients diagnosed with Schedule for Affective Disorders and Schizophrenia/Research Diagnostic Criteria (SADS/RDC) as having major depressive disorder (MDD). We compared absolute and dichotomous DST values (DST suppression versus nonsuppression) with absolute and dichotomous measures of endogeneity (as measured by operationally defined RDC items) and with Hamilton Rating Scale for Depression (HRSD) scores that were collected immediately prior to treatment. We found that degree of endogeneity correlated moderately (r = 0.27) but significantly (p = 0.02) with absolute DST values; DST nonsuppression increased proportionately with changes in categorical endogenous subtype (0% of the nonendogenous patients were nonsuppressives, 52% of probable endogenous, and 61% of subjects definitely endogenous); mean values for maximum DST concentrations increased steadily with categorical endogeneity (nonendogenous, 1.44 microgram/dl; probable endogenous, 7.65 micrograms/dl; definite, 10.93 micrograms/dl; p = 0.01); HRSD scores correlated more strongly (r = 0.45, p = 0.000) with maximum DST levels than did the degree of endogeneity. Age and weight changes did not account for the relationship of endogeneity to DST values. These data suggest that maximum postdexamethasone plasma cortisol levels reflect overall severity of depression and endogeneity and that endogeneity per se is highly confounded with severity.
Insights
The Dexamethasone Suppression Test (DST) appears to measure both depression severity and endogeneity. Higher DST levels correlate with more severe depression and endogenous subtypes, suggesting endogeneity is linked to overall illness severity.
Area of Science:
- Psychiatry
- Neuroendocrinology
- Clinical Psychology
Background:
- The Dexamethasone Suppression Test (DST) is a diagnostic tool used in psychiatry.
- Debate exists on whether DST results reflect clinical severity or the degree of melancholia (endogeneity) in patients with major depressive disorder (MDD).
Purpose of the Study:
- To investigate the relationship between DST results and measures of endogeneity and depression severity.
- To determine if DST reflects clinical severity or endogeneity in major depressive disorder.
Main Methods:
- Studied 73 drug-free inpatients diagnosed with major depressive disorder (MDD) using Schedule for Affective Disorders and Schizophrenia/Research Diagnostic Criteria (SADS/RDC).
- Compared DST values (absolute and dichotomous suppression/nonsuppression) with endogeneity measures (operationally defined RDC items) and Hamilton Rating Scale for Depression (HRSD) scores.
- Analyzed correlations between DST, endogeneity, and HRSD scores, controlling for age and weight.
Main Results:
- Degree of endogeneity moderately correlated with absolute DST values (r = 0.27, p = 0.02).
- DST nonsuppression rates increased with endogenous subtype: 0% nonendogenous, 52% probable endogenous, 61% definite endogenous.
- HRSD scores correlated more strongly with maximum DST levels (r = 0.45, p = 0.000) than with endogeneity.
- Mean maximum DST concentrations increased significantly with categorical endogeneity (p = 0.01).
Conclusions:
- Maximum postdexamethasone plasma cortisol levels reflect both overall depression severity and endogeneity.
- Endogeneity in major depressive disorder is highly confounded with illness severity.
- DST results provide a measure that integrates both severity and endogenous features of depression.