In order to diagnose Adult ADHD, specialists like those at ADHD services in London count on assessment tools that include checklists, rating scales and history forms. Each tool will serve a distinct purpose.One of the tools used in assessing Adult ADHD is the Symptom Checklist for adults. This is provided in the form of a checklist that helps in determining if ADHD symptoms are indeed present. It also shows when these symptoms may appear, when they began and whether you suffer impairment because of the symptoms.