Circadian secretion of cortisol in bipolar disorder.

OBJECTIVE: To compare the 24-h cortisol secretion profiles of normal control subjects and patients with bipolar disorder who were in the depressive, manic and euthymic phases of the disorder. PARTICIPANTS: Eighteen patients, 25-62 years of age, in depressed (n = 5), manic (n = 5) or euthymic (n = 8) phase of bipolar disorder recruited through a psychiatric outpatient clinic, and 5 control subjects, 24-41 years of age, recruited through advertisement or word of mouth. OUTCOME MEASURES: Subjects were interviewed and symptom ratings were obtained using the Hamilton Depression Rating Scale, Beck Depression Inventory and Young Mania Scale. Blood collection began at 0800 and continued at hourly intervals for 24 h. Serum cortisol levels were assayed using a validated commercial radioimmunoassay kit.
RESULTS: An analysis of variance of the area under the cortisol 24-h time-concentration curve (AUC) revealed a significant difference between the control group and patient groups (F = 3.69, p = 0.03). the mean AUCs of the patients in the depressed (263.4 micrograms/dL) and hypomanic (262.2 micrograms/dL) phases were beyond the 95% confidence interval for the controls (120.9-253.3 micrograms/dL). There were no significant group differences in cosinor acrophase and no significant effects of sex, education, age of illness onset, duration of illness or duration of mood state at time of testing on the cortisol measures. Pearson correlations between symptom rating scores and cortisol secretion variables were not significant.
CONCLUSION: The increases in cortisol secretion in patients in both the depressed and manic phases of bipolar disorder suggest that cortisol level is probably not a state marker in bipolar disorder.