Evaluation of the Effectiveness of an Internet-Based Cognitive Behavioral Intervention on Sleep Quality, Insomnia Severity, and Daytime Sleepiness in Persian-Speaking Adults With Insomnia

Inclusion Criteria

Inclusion Criteria: * Age between 18 and 60 years. * Meets diagnostic criteria for insomnia disorder according to DSM-5, based on clinical interview or a validated screening procedure. * Insomnia Severity Index (ISI) score ≥ 10, indicating at least subthreshold insomnia. * Reports difficulty initiating or maintaining sleep or early-morning awakenings at least three nights per week for at least three months, with associated daytime impairment (e.g., fatigue, concentration problems, irritability). * Able to read and understand Persian. * Has regular access to the internet and a smartphone and/or computer to use the Omid web-based program. * Willing and able to provide informed consent and to complete online questionnaires and daily sleep diaries. Exclusion Criteria: * Uncontrolled medical or neurological conditions that significantly interfere with sleep or require immediate treatment (e.g., untreated moderate-to-severe obstructive sleep apnea, uncontrolled epilepsy, unstable cardiac disease, advanced cancer). * Current shift work or rotating work schedules that regularly disrupt nighttime sleep. * Pregnancy. * Participation in another clinical trial or research study that could affect sleep during the study period. * Ongoing structured psychotherapy specifically targeting insomnia or other major psychiatric conditions within the past 6 months. * Current major depressive disorder or other severe psychiatric disorder (e.g., bipolar disorder, schizophrenia, psychotic disorders), as determined by clinical assessment or structured interview. * Evidence of problematic substance use, such as heavy alcohol use (more than approximately 3 standard drinks per day on most days of the month) or frequent misuse of recreational drugs (e.g., cannabis use more than once per week), in the judgment of the investigators. * Active suicidal ideation or behavior requiring urgent clinical intervention. * Primary diagnosis of another untreated sleep disorder (e.g., restless legs syndrome, narcolepsy, circadian rhythm sleep-wake disorder) where insomnia is not the main problem. * Having an infant or child under 2 years of age whose care regularly disrupts nighttime sleep, in the judgment of the investigators.