A 25-Year-Old Man Comes for a Follow-Up Examination 6 Weeks

A 25-year-old man comes for a follow-up examination 6 weeks after beginning sertraline therapy for major depressive disorder. He takes the medication as prescribed but his mood has barely improved. The patient appears anxious and reports that he still feels sad and hopeless most of the time. He denies suicidal ideation. He is more tired than usual and often feels drowsy during the day. The patient has difficulty concentrating at work and has missed two important deadlines; he worries that he might soon lose his job. Which of the following is the most likely explanation for this patient's lack of response?

A) Comorbid anxiety disorder
B) Development of tolerance
C) Inadequate duration of treatment
D) Medication side effect
E) Poor treatment adherence
F) Treatment-resistant depression