A 14-year-old male with attention-deficit/hyperactivity disorder, combined presentation, was initially treated with methylphenidate extended-release, titrated to 54 mg daily over six weeks. His baseline Vanderbilt ADHD Rating Scale parent score was 38 and teacher score was 42. On methylphenidate 54 mg, his parent score improved to 28 and teacher score to 30, representing approximately 25-30% improvement. However, his parents report the medication effect wears off by 3 PM, leaving him unable to complete homework or participate in after-school activities. He also developed appetite suppression with a 4-pound weight loss. The PMHNP decided to cross-titrate to mixed amphetamine salts extended-release 20 mg daily. After four weeks on amphetamine, his parent Vanderbilt score is 18 and teacher score is 20, representing a 50-55% improvement from baseline. Coverage extends through homework time, appetite has improved, and he has regained 2 pounds. He reports occasional difficulty falling asleep, resolved by moving the dose to early morning. The PMHNP is evaluating the differential response pattern. Which of the following best represents the appropriate evaluation?