Which of the following is a common symptom of attention deficit hyperactivity disorder (ADHD)?

Hyperactivity is a hallmark symptom of attention deficit hyperactivity disorder (ADHD). Individuals with ADHD often exhibit excessive movement, difficulty remaining still, and a general restlessness that can manifest in behaviors such as fidgeting or talking excessively. This symptom is particularly evident in environments requiring sustained attention and impulse control, such as classrooms or during quiet activities. Hyperactivity can vary in intensity; some individuals may display more impulsive behaviors, while others might primarily struggle with inattentiveness.

Considering the other potential symptoms listed, they don't align with ADHD as closely as hyperactivity does. Severe anxiety may co-occur with ADHD but is not a core characteristic of the disorder itself. Delusions are more associated with psychotic disorders rather than ADHD. Lastly, excessive sleepiness is not typically recognized as a symptom of ADHD; individuals might struggle with sleep due to their symptoms, but it's not a defining feature of the disorder. Therefore, hyperactivity stands out as a fundamental symptom characteristic of ADHD.