A Comparison of Group Cognitive Behavioural Therapy (CBT) and Structured Activity Group for Adults With Attention Deficit Hyperactivity Disorder (ADHD)

Many adults with attention deficit hyperactivity disorder (ADHD) experience difficulties with inattention, planning, impulsivity and emotion regulation that impacts work and social life negatively also after treatment with medication. There are various psychological treatments aiming to improve these symptoms, but it is not known if they work or not. The goal of this clinical trial is to evaluate group cognitive behavioural therapy (CBT) for adults with attention deficit hyperactivity disorder (ADHD) in comparison to an active control group consisting of a discussion and activity group. Previous research suggests that group CBT works about equally well as other structured group activities. The main questions the researchers aim to answer are if group CBT work better than activity groups to: * Improve symptoms of ADHD * Improve general mental health and life quality * Improve every-day functioning The researchers also want to learn if group CBT or activity groups work better for some people with ADHD depending on individual characteristics such as * Type of symptoms, age, gender or co-occurring psychiatric diagnoses The comparison is a manualised structured activity group given at the same number of sessions and same group size. All participants will visit our clinics at 14 occasions. They will: * Fill in questionnaires before and after the group intervention, and online after 6, 12 and 24 months * Do an interview with an independent trained clinician about their daily functioning and difficulties related to ADHD symptoms before and after the group intervention, and after 6, 12 and 24 months