This study evaluates two behavioral treatments for patients with insomnia disorder: Bedtime Restriction Therapy (BRT) and Cognitive Behavioral Therapy for Insomnia (CBT-I). Both therapies aim to improve the clinical symptomatology of insomnia by teaching participants techniques to better manage their sleep schedule and habits. BRT is a simpler and shorter therapy focused on aligning the time spent in bed with reported sleep time. CBT-I includes additional components such as relaxation techniques and cognitive exercises. The study will compare these treatments to see if BRT is as effective as CBT-I in improving the clinical symptomatology of insomnia.

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