To the Editor: We read with great interest the report by Charles DeBattista, D.M.H., M.D., and co-authors (1) of their double-blind, placebo-controlled trial with depressed patients in which the patients who received 15 mg of intravenous hydrocortisone demonstrated a significantly greater reduction in Hamilton Depression Rating Scale scores over a 24-hour period than those who received placebo or ovine corticotropin-releasing hormone. This mood-elevating effect of hydrocortisone has previously been noted by Goodwin et al. (2). The authors considered a number of explanations for the finding of the antidepressant-like effects of hydrocortisone injections. They hypothesized that the hydrocortisone may have enhanced negative feedback and thereby reduced hypothalamic-pituitary-adrenal axis activity overall, enhanced dopamine activity, corrected a state of hypocortisolemia, or increased β endorphin levels. We suggest an alternative explanation—namely, that the antidepressant effect of hydrocortisone may have been mediated by means of the serotonin (5-HT) system.

The antidepressant effects of tricyclic antidepressants, serotonin-specific reuptake inhibitors, lithium, and ECT are possibly mediated by an attenuation of inhibitory somatodendritic 5-HT_1A receptor function, with a subsequent facilitation of 5-HT transmission (3). Elevated plasma cortisol levels, induced by acute stress or administration of hydrocortisone, attenuate somatodendritic 5-HT_1A receptor function in both mice and humans, thereby facilitating 5-HT_1A neurotransmission in an antidepressant-like manner (4–6). This is in marked contrast to the effects of long-term elevation of corticosteroids, which reduce postsynaptic 5-HT_1A receptor numbers, an effect that may promote depression (7). We propose that this attenuation of somatodendritic 5-HT_1A receptor function is the basis of the mood-elevating effects produced by hydrocortisone in the study by Dr. DeBattista et al. and illustrates a potential neurobiological basis of resilience in the face of psychosocial stress. Failure of this response, due, for example, to deficient glucocorticoid receptor function, may be central to the development of depressive illness (8).