A 38-year-old woman presents to the psychiatry clinic with a 3-month history of persistent low mood, loss of interest in her work as a software engineer, and early morning awakening at 4 AM. She reports significant guilt about being a burden to her family, difficulty concentrating on tasks, and a 6 kg weight loss. She denies suicidal ideation but admits to passive death wishes. Her past medical history includes hypothyroidism (TSH normal on levothyroxine). Vital signs are stable; physical examination is unremarkable. What is the most appropriate next step in the management of this patient?