A 14-year-old boy is being treated for behavioral difficulties at home and at school and has been diagnosed with ADHD. He has been skipping class and often comes home smelling of cigarette smoke. His parents report he has developed sudden facial twitches and makes more frequent repetitive guttural sounds, especially since starting a new medication. His drug screen is negative for unprescribed substances of abuse. Which of the following is the most likely cause of his facial twitches and guttural sounds?

Choice A reason: Nicotine use can cause stimulation and mild physical effects but is unlikely to produce sudden onset of facial tics or guttural sounds in this context. Choice B reason: Atomoxetine, a non-stimulant ADHD medication, is less commonly associated with movement disorders or tics. Choice C reason: Guanfacine is primarily sedating and generally does not precipitate new tics or stereotyped movements. Choice D reason: Stimulant medications such as amphetamines (Adderall) can exacerbate or precipitate tics in children with ADHD. The temporal relationship between starting the new medication and the onset of tics strongly implicates amphetamine as the cause.