Comparative Efficacy of BRT and CBT-I for Insomnia

• Cognitive behavioral therapy for insomnia (CBT-I) (Behavioral): Cognitive Behavioral Therapy for Insomnia (CBT-I) is a gold-standard, evidence-based treatment combining techniques to improve the clinical symptomatology of insomnia. Delivered in six 90-minute group sessions over six weeks, it includes: sleep education (i.e. understanding sleep mechanisms and influencing factors), bedtime restriction (i.e. aligning bedtimes with reported sleep duration), stimulus control (i.e. getting out of bed when unable to sleep), cognitive therapy (i.e. addressing dysfunctional sleep beliefs), relaxation techniques (i.e. using methods like progressive muscle relaxation).
• Bedtime restriction (BRT) (Behavioral): Bedtime Restriction Therapy (BRT): A behavioral intervention aimed at improving the clinical symptomatology of insomnia by aligning time spent in bed with reported sleep duration. Participants attend four 60-minute group therapy sessions over six weeks. The intervention includes: setting individualized sleep windows based on sleep diaries, regular adjustment of sleep schedules to enhance sleep pressure, group discussions to address implementation challenges and maintain motivation. BRT focuses exclusively on bed time restriction without additional cognitive or relaxation components, making it a simplified, resource-efficient approach to treating insomnia.

Primary outcomes

• Insomnia Severity Index (ISI) summary scores [Baseline (T0) to 6 weeks (T1), 3 months (T2), and 6 months (T3)]

Sex: All, ages: 18 Years to 80 Years

Inclusion Criteria:

* Must meet DSM-5 criteria for insomnia disorder.
* Adults aged 18 to 80 years
* Capable of giving written informed consent.
* Sufficient fluency in the study site's language (i.e., German or French) to understand all study-related information.

Exclusion Criteria:

* Unstable, progressive, or degenerative medical condition
* Acute pain or poorly managed chronic pain
* Suicidality
* Uncontrolled psychiatric condition requiring treatment outside of study
* Alcohol or drug abuse or dependency
* Diagnosis of psychosis, bipolar disorder, autism, borderline personality disorder, or antisocial personality disorder
* Clinical evidence of sleep disorders other than insomnia (e.g., sleep apnea, restless legs, periodic limb movements in sleep, parasomnia)
* Evidence of intellectual disability
* Regular intake of benzodiazepines (BZD) or benzodiazepine receptor agonists (BZDRA)
* Alteration of medication within 4 weeks prior to study treatment or planned alteration during the trial period (stable medication except BZD or BZDRA does not lead to exclusion)
* Current other psychotherapy for insomnia
* Known pregnancy or breastfeeding
* Inability to comply with study procedure
* Insufficient fluency in German or French to complete the study