A 42-year-old male has been on fluoxetine 40 mg daily for four months for major depressive disorder. His PHQ-9 score has improved from 20 to 8. He reports his mood is no longer depressed, he is sleeping well, appetite is normal, and he has no suicidal ideation. However, he describes feeling emotionally flat, stating he does not feel sad but also does not feel joy or excitement. He reports decreased motivation, reduced interest in hobbies he previously enjoyed, and a sense of not caring about things that used to matter to him. His wife has noticed he seems emotionally detached. The PMHNP is evaluating whether these symptoms represent residual depression or a medication side effect. Which evaluation is most accurate?