Adult ADHD diagnosis waiting lists in the NHS leave thousands of adults undiagnosed for years, despite ADHD affecting around 1 in 20 people. Written by a GP specialising in adult ADHD, this article explains why NHS waiting times are so long, the impact of delayed diagnosis, why many adults feel forced to go private, and how untreated ADHD costs society an estimated £17 billion each year through lost productivity, poor health outcomes, and reduced economic participation.