ABSTRACT
The standard error of the mean (SEM) is used to calculate the 95" confidence interval (CI) for the mean. It can also be used to calculate other confidence intervals around the mean. The two other most common are the 68" and the 99" CIs. Patients were recruited at the specialist attention deficit hyperactivity disorder (ADHD) service of the Radboudumc outpatient department of psychiatry. Participants were randomly allocated to Mindfulness-Based Cognitive Therapy (MBCT) or waitlist (WL) control condition by an independent researcher. The mindfulness training was adapted from the MBCT protocol developed for recurrent depression. The MBCT groups were instructed by two experienced mindfulness teachers: a psychiatrist specialized in ADHD with 10 years of experience as a mindfulness teacher and a qualified nurse specialist meeting the advanced criteria of the Association of Mindfulness-Based Teachers in the Netherlands and Flanders. ADHD symptoms were assessed by a clinician with the investigator rating version of the Conners' Adult ADHD Rating Scale.
