Can someone fail an ADHD assessment just by being too calm or composed during it?

Not by itself, no, though presentation on a given day is one thing a clinician notices. A skilled assessor accounts for the fact that a formal appointment is a structured, novel, often high-interest situation, exactly the kind of context where someone with ADHD can sometimes perform better than in their everyday, less structured environment. That's why assessments rely on history and multiple data sources rather than in-session observation alone; a calm, composed appointment doesn't override a documented pattern of impairment reported across school, work, and home settings over time. FasTreat also offers private online ADHD assessment and ongoing care, depending on your needs and clinical assessment. Related reading: https://www.fastreat.com/en/adhd-faq References: https://www.caddra.ca/wp-content/uploads/Canadian-ADHD-Practice-Guidelines-4.1-January-6-2021.pdf