This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Mood Disorders, Subject name: Psychiatry
[{'content': 'The most common comorbid illness with depression is \nSelect and explain. \nA. Anxiety disorder, B. Substance use disorder, C. Obsessive-compulsive disorder, D. Comorbid illnesses are rare', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Substance use disorder is the commonest comorbid psychiatric illness. The other impoant ones are panic disorder, social anxiety and OCD. Substance use is more common in men depressives and anxiety in women depressives. Bipolar disorder patients have twice the rates of prevalence, in comparison to the unipolar depressive patients.', 'role': 'assistant'}]