This thesis examines how self-experimentation can support health behavior change for young adults with ADHD. The work speaks to a gap in ADHD research that rarely addresses health promotion as a lived, day to day practice. The central question guiding the project is: What role might self-experimentation play in the health behavior change process of young adults with ADHD?

Methodologically, the project uses Research through Design with participatory methods to generate situated insight rather than a fixed solution. The study unfolds across four phases that move from context to concept, from interaction to impact. Activities include co-creation with ADHD participants, expert interviews, iterative prototyping, user testing, and reflective sessions. In Phase 1, three co-creation sessions engaged nine students with ADHD, complemented by interviews with five experts. Phase 2, is where ideation activities take place and a concept for SE for ADHD is developed. In Phase 3, a first self-experimentation toolkit was prototyped and tested over two weeks, followed by a group session. In Phase 4, a refined toolkit was tested for two weeks by seven participants, followed by one on one interviews.

Two design artefacts structure the inquiry. Prototype 1 introduced a friendly, low-barrier toolkit built around the idea of consistency over perfection, with two foldable journals, a map, and a compass to support planning, tracking, and reflection. Prototype 2 consolidated use into a single foldable journal with optional stickers and a digital guide, aiming to reduce fragmentation and make the two week journey visible and easier to sustain. Both prototypes follow a three-step self-experimentation cycle of Plan, Track, and Reflect adapted for ADHD.

Across phases, three contributions emerge. First, Phase 1 introduces Dropout States as a framing for moments when ADHD users are most likely to disengage. These tags capture recurrent pitfalls such as Overwhelm, Perfectionist, Negative, Low Stimulation, and Unaccountable, and help explain why well-intended plans fail. Second, a complementary set of Guiding Principles is articulated to counter these pitfalls, including Simplicity, Guidance, Positivity, Stimulation, Accountability, Visibility, Flexibility, and Sensemaking. Third, the project defines SE as a potential reframing tool for ADHD individuals. Together, these elements form a practical lens for designing tools that help people show up, learn, and adjust.

Findings show that self-experimentation can reframe the change process in useful ways. Participants described relief from perfection pressure, better organization of mental clutter, clearer translation of intentions into concrete actions, and more individualized strategies that fit current context. At the same time, the approach introduces frictions that matter in ADHD. Many participants relied on external accountability, reported cognitive effort at key steps such as planning and daily documentation, and found hybrid or purely physical formats hard to keep accessible in daily life. These insights position self-experimentation as a promising tool for initiating change and building self-knowledge, provided that tools include supportive structures and minimize effort.

The project proposes a Progressive Engagement Model as a way to align the method with ADHD needs. In this model, people begin with short, guided micro-experiments that are playful and low effort, then shift toward greater autonomy only as readiness and confidence grow. This direction sits alongside clear limitations of the study, including two-week trials, a sample of eleven ADHD participants and five experts across phases, heavy reliance on qualitative evidence, and the potential influence of researcher facilitation on engagement.

In sum, self-experimentation is not a single solution. It is a practical way to potentially reframe health behavior change for young adults with ADHD, making the process more forgiving, organized, actionable, and personally relevant, as long as design choices reduce cognitive load and bring in accountability where needed. Ultimately, this thesis contributes to a body of research that seeks to understand ADHD not only through deficits but through contextual and experiential knowledge. By investigating self-experimentation not as a fix, but as a reflective and adaptive process, the project highlights the value of designing with neurodiverse users. Breaking the cycle means more than disrupting habits, it means challenging assumptions about what change should look like.