Major Depressive Disorder

Which of the following neurotransmitter systems is primarily implicated in the pathophysiology of Major Depressive Disorder according to the monoamine hypothesis?

A 52-year-old man with a history of Major Depressive Disorder, currently on sertraline 100 mg daily for 8 weeks, returns to the psychiatry clinic. He reports persistent depressed mood, anhedonia, and fatigue despite compliance with medication. His wife notes no improvement in his social withdrawal or irritability. Vital signs are stable, and there are no contraindications to dose escalation. What is the most appropriate next step in management?

According to DSM-5 criteria, what is the minimum duration of symptoms required for a diagnosis of Major Depressive Disorder?

A 38-year-old woman presents with a 3-week history of persistent depressed mood, anhedonia, sleep disturbance, and feelings of worthlessness. She has no significant past psychiatric history and no contraindications to antidepressants. Which is the drug of choice for first-line treatment of her major depressive disorder?

A 52-year-old man with major depressive disorder and chronic neuropathic pain from diabetic peripheral neuropathy presents for antidepressant initiation. He has no cardiac contraindications. Which antidepressant is most appropriate as first-line therapy given his comorbid pain condition?