The risk for comorbid major depressive disorder and obesity is increased in adolescents and adults with attention-deficit / hyperactivity disorder (ADHD), and adolescent ADHD predicts adult major depressive disorder and obesity. Non-pharmacological interventions to treat and prevent these comorbidities in patients with ADHD are urgently needed. Under the umbrella of the CoCA project, a pilot clinical trial will provide new insight about the potential of bright light therapy and physical exercise – two non-pharmacological, inexpensive, and easy accessible interventions – to prevent depression and obesity in adolescents and young adults with ADHD. These interventions will be supported by a mobile Health App application. This intervention will be accompanied by neuroimaging studies in patients.This trial is NOW ready to start at the Frankfurt site. All outpatients with ADHD aged 14 to 30 years old living in and around Frankfurt am Main are invited to participate in the trial. Recruitment at the other clinical sites (Barcelona, London and Nijmegen) will start soon afterwards.