Introduction: Attention deficit hyperactivity disorder (ADHD) is the most common neurodevelopmental disorder, affecting 2-7% of adults worldwide. Adults with ADHD face increased levels of stress and fatigue, frequently contributing to exhaustion. They are at higher risk for stressful life events and mental health issues, with a majority of meeting criteria for at least one comorbid psychiatric disorder. Additionally, adults with ADHD have more sickness absence days compared to controls, possibly twice or several times as many. Although research on assessing and treating adult ADHD is growing, many individuals remain undiagnosed and untreated due to lack of recognition, misconceptions, and limited access to psychiatric care. Internet-delivered interventions offer a promising solution for improving access to care and effec- tively disseminating psychological treatments. However, their efficacy for adult ADHD remains underexplored.

Methods: This study will involve 240 participants, randomly assigned to one of three conditions: Internet-based cognitive-be- havioral stress-management; Internet-based mindfulness stress-management; or a wait-list control. Participants in the intervention groups will engage in twelve-week, twelve-module programs, with clinical support available on demand. Both interventions have an explicit focus on workplace functioning, but differ in their content. The cognitive behavioral program is based on cognitive behavioral therapy (CBT) principles, including both tailored and transdiag- nostic applications. The mindfulness program is based on a well-established skills-training manual for adult ADHD. Outcome measures include self-reported quality of life (primary outcome), symptoms of ADHD, perceived stress, symptoms of exhaustion, depression, and anxiety. Additionally, participants from both intervention groups will be interviewed to explore their experiences with the programs.

Discussion: Previous research indicates a positive attitude toward internet-delivered psychological interventions among adults with ADHD. A previous single-arm open trial has also indicated the potential of the current cognitive-behavioral stress-management intervention. This study aims to further assess its efficacy by comparing it to an active control intervention, thereby accounting for the expectation of benefit and common factors of internet interventions. The additional inclusion of a wait-list control will help account for spontaneous improvement and regression toward the mean. If the cognitive-behavioral intervention shows further promise, it could be further developed and potentially disseminated more broadly, either through routine healthcare systems or as a product. Given the position of ADHD adults in the labor market and the costs of sickness absence for all social partners, demonstrating effective inter- ventions for this population could have significant socio-economic benefits, reducing both individual and societal burdens.