After an adolescent diagnosed with attention deficit-hyperactivity disorder (ADHD) begins methylphenidate (Ritalin) therapy, a nurse notes that the adolescent loses 10 pounds in a 2-month period. What is the best explanation for this weight loss?

A. Side effects of Ritalin cause nausea; therefore, caloric intake is decreased: Nausea can occur as a side effect, but appetite suppression is a more common and direct cause of weight loss with methylphenidate. Nausea alone does not fully account for gradual weight changes over months. B. Increased ability to concentrate allows the client to focus on activities rather than food: Improved concentration may lead to reduced distractions, but the primary mechanism for weight loss is pharmacological appetite suppression rather than distraction from eating. C. Hyperactivity seen in ADHD causes increased caloric expenditure: While hyperactivity may burn additional calories, weight loss observed after starting methylphenidate is more strongly linked to decreased appetite than baseline activity levels. D. The pharmacological action of Ritalin causes a decrease in appetite: Methylphenidate stimulates the central nervous system, which commonly reduces hunger and caloric intake. Appetite suppression is a well-documented side effect that can lead to measurable weight loss in adolescents.