WELT-REST: WELT Randomized Evaluation of Sleep Therapy

The goal of this clinical trial is to learn whether the SleepQ mobile app can help reduce insomnia symptoms in adults diagnosed with insomnia. The main questions it aims to answer are: * Does adding the SleepQ app to care as usual (CAU) improve insomnia symptoms after 12 weeks? * Does SleepQ also improve depressive symptoms, anxiety, beliefs about sleep and daily functioning? Researchers will compare CAU + SleepQ to CAU alone to see whether SleepQ provides additional benefits for sleep and well-being. Participants will take part remotely from home, be randomly assigned to either SleepQ+CAU or CAU alone, and complete online questionnaires at baseline, week 6, and week 12 about their sleep, mood, and daily functioning. Participants in the intervention group will use the SleepQ app for 12 weeks while continuing their usual care.