The use of glucocorticoids is a prevalent and important treatment for patients with rheumatic disease, back pain, severe allergic reaction, and so forth by both primary care and medical specialists. Often those prescribing these powerful medications are not aware of the potential side effects and problematic sequelae. Increasing numbers of anecdotal reports, as well as a few small empirical clinical studies, associate the following with glucocorticoid treatment: mood instability, unmasking of bipolar disorders, depression, psychosis, and even suicide. The causes associated with these negative outcomes and their underlying mechanisms have, up until now, not been well understood. This volume presents a “state-of-the-science” report on glucocorticoids and mood, and the proposed mechanisms of the negative sequelae from glucocorticoid treatment.