A 67-year-old woman with a history of obesity, chronic low back pain, and recurrent episodes of major depression presents with mild depressive symptoms of more than 2 years’ duration, with worsening symptoms over the past 4 months. She was receiving sertraline at a stable dose of 100 mg per day until 3 months ago, when she initially presented for her worsening depressive symptoms. At that time, sertraline was tapered off, and treatment with extra-long extended-release bupropion (bupropion XL) was started at a dose of 150 mg daily and was increased to 300 mg daily 3 weeks later. Despite having taken the higher dose of bupropion XL for more than 2 months, the patient continues to have low mood, loss of interest in usual pleasurable activities, trouble falling asleep, wakefulness several times during the night, diminished energy, poor appetite, difficulty concentrating, and intrusive thoughts of being “better off dead,” but she does not have active suicidal thinking. Her nine-question Patient Health Questionnaire (PHQ-9) score is 17 (on a scale of 0 to 27, with higher scores indicating greater severity of depressive symptoms). How would you evaluate and treat this patient?