How Much Does A Private ADHD Diagnosis Cost? You might have to take the private option if you are an adult who suffers from ADHD. This is a good option because private psychiatrists are more experienced in diagnosing adults suffering from ADHD. They also test them for co-morbidities like anxiety http://www.stes.tyc.edu.tw/xoops/modules/profile/userinfo.php?uid=1556594