Impaired mitogen-induced lymphocyte responses and the hypothalamic-pituitary-adrenal axis in depressive disorders

The lymphocyte stimulation responses to the mitogens phytohemagglutinin (PHA), concanavalin A (Con A) and pokeweed (PWM) were investigated in 30 hospitalized depressed women undergoing a dexamethasone suppression test (DST). Patients were classified according to DSM-III as having major depression with melancholia, without melancholia, and minor depression. The Hamilton Depression Rating Scale (HDRS) and the State-Trait Anxiety Inventory (STAI) were measured. Patients with major depression showed significantly decreased lymphocyte stimulation induced by PHA, Con A, and PWM as compared to those with minor depression. These differences could not be attributed to age, body weight, weight loss, total number of leukocytes, menopausal status, sleep disturbances, concomitant use of low-dosage benzodiazepines or length of drug-free period before testing. The group mean differences in lymphocyte stimulation counts were not affected by the severity of illness or the severity of state and trait anxiety. There were no significant differences in the lymphocyte responses to PHA, Con A, and PWM between DST non-suppressors and DST suppressors. No significant correlations were established between baseline and post dexamethasone cortisol values and the lymphocyte stimulation counts.