A 28-year-old woman has recently developed severe mood swings, depressed mood, anhedonia, and suicidal ideation. She also has episodes of irritability, racing thoughts, and insomnia. She has Crohn disease and has been taking daily prednisone for the past 4 weeks. She has no past psychiatric history. Using the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders, what is the most probable psychiatric diagnosis? Bipolar affective disorder Generalized anxiety disorder Major depressive disorder Medication-induced depressive disorder