Attention-deficit hyperactivity disorder (ADHD) is a condition that develops during childhood and affects 6–10% of kids and 2–6% of adults. People with ADHD have either mainly inattentive symptoms (such as lacking concentration), mainly hyperactive and impulsive symptoms (such as speaking or acting without thinking), or a combination of the two. Two people with ADHD can have very different symptoms and experiences. So it’s important for clinicians who diagnose the condition to have the right knowledge and expertise. But our new research found half of psychologists who assess for ADHD don’t follow the diagnostic guidelines or criteria.