A 38-year-old male with bipolar I depression has been taking lurasidone 80 mg daily for 8 weeks, prescribed after a partial response to lurasidone 40 mg. Despite the dose increase 4 weeks ago, he reports persistent depressed mood, hypersomnia, and anhedonia with minimal improvement. He states he takes the medication reliably every morning with coffee and a piece of toast before rushing to work. He denies missed doses. His previous provider is considering switching to a different medication for treatment failure. The PMHNP reviews his medication-taking routine in detail. Which of the following is the most likely explanation for this patient's apparent non-response?