Efficacy of Smartphone-Based Digital Brief Behavioral Treatment for Insomnia with Adjunct Light Therapy in Young Adults with Insomnia Symptoms and Late Chronotypes: A Three-Arm Randomized Controlled Trial Protocol

Background: Insomnia symptoms associated with late chronotypes are prevalent among young adults, and frequently lead to sleep deprivation, morning-awakening difficulties, and excessive daytime sleepiness. These conditions are associated with psychological distress, impaired academic functioning, and reduced self-esteem. Although chronobiological behavioral interventions are effective, their accessibility remains limited. To bridge this gap, we developed a smartphone application delivering digital brief behavioral treatment for insomnia (BBT-I). We also designed a four-week program integrating the app with light therapy (LT) via wearable glasses named “Digital BBT-I + LT”. This randomized controlled trial will evaluate the efficacy of digital BBT-I with LT and digital BBT-I alone compared with a waitlist control group. Methods: This three-arm parallel-group randomized controlled trial will target young adults with insomnia symptoms and late chronotypes. Participants will be randomized to receive digital BBT-I with adjunctive LT, digital BBT-I alone, or a waitlist control condition. The primary outcome will be insomnia symptom severity, assessed using the Insomnia Severity Index. Evaluations will be conducted at baseline, weekly during the four-week intervention period (days 8, 15, 22, and 29), and at the 3-month follow-up. Discussion: Late chronotypes and insomnia significantly impair sleep and mental health in young adults. Despite the recognized importance of chronobiology-based treatments, they are rarely adopted as standard care. This highlights the need for scalable digital interventions, such as digital BBT-I. By rigorously assessing these strategies, this trial aims to provide clinical evidence regarding accessible interventions to improve sleep and mental health outcomes in this population.