ADHD Assessment - Why it's Important to Get a Private ADHD Diagnosis Anyone who suspects they have ADHD but hasn't been diagnosed with it should undergo an ADHD assessment. The process can last up to two hours, and it's recommended to bring an adult family member or a friend along. https://archertvsni.get-blogging.com/30336169/a-productive-rant-about-adhd-diagnosis-uk-private