This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Psychiatry
[{'content': 'Episodes of depression in major depressive disorder tend to: \nSelect and explain. \nA. Increase in frequency with age, B. Decrease in length with age, C. Last for about 9 months when treated, D. Have a rapid onset', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Episodes of major depression tend to increase in both length and frequency with age. When treated, episodes of major depression last for about 3 months. If untreated, depression lasts from 6 to 12 months. Episodes of major depression often have a gradual onset and occur an average of 5 to 6 times over a 20-year period.', 'role': 'assistant'}]