Participants assigned to the intervention group will receive first the intervention. They will complete various assessment at baseline (T0), post-intervention after the 3 weeks of intervention (T1), and 3 months after the end of the intervention (T2).

Participants assigned to the waitlist control group complete a baseline assessment (T0), a second assessment after 3 weeks of waiting (T1), and then receive the intervention. They are assessed again after the intervention (T2) and at 3-month follow-up (T3). This design allows for pre- and post-intervention comparisons while ensuring delayed access to the program.

The intervention consists of three structured sessions delivered over three weeks, with additional online follow-ups. Each session lasts 1.5 hours and takes place in the evening, with a one-week interval between sessions.

Session 1 focuses on providing fundamental knowledge about sleep health. Session 2 introduces behavioral strategies to improve sleep health and asks participants to implement behavior change intentions.

Session 3 reviews the implementation of the intention, the changes made or not, and addresses the relationship between stress and sleep, along with coping strategies.

RU-SATED is the instrument used to measure sleep health. Sleep health varies according to individual, social and environmental conditions, and emphasises that good sleep is not simply the result of an absence of sleep disorders. In terms of its components, sleep health relates to (1) sleep duration, or the total number of hours of sleep obtained over 24 hours, (2) sleep efficiency, corresponding to the ease or otherwise with which an individual falls asleep and returns to sleep, and (3) timing, or how our sleep fits into a 24-hour day, (4) alertness, or sleepiness, which concerns a person's ability to maintain a state of attentive wakefulness throughout the day, (5) satisfaction, or subjectively represented sleep quality, and finally (6) sleep regularity.

More specifically, RU-SATED score is distributed between 0 and 12, with the higher the score, the better the person's sleep health.

Sleep satisfaction will be assessed using a single-item question from a sleep diary completed by participants each morning for seven consecutive days. The item reads: "How would you rate the quality of your sleep?" Responses are recorded on a 5-point Likert scale ranging from 1 ("very restless") to 5 ("Very deep"). Daily scores will be summed to obtain a total sleep satisfaction score ranging from 7 to 35. Higher scores indicate a higher perceived sleep quality. The measure provides a subjective evaluation of sleep quality from the participant's perspective.

Self-reported bedtime and wake-up time recorded daily in a sleep diary. Used to calculate the timing of sleep onset and wake time, as well as midpoint of sleep.

This outcome is assessed students' beliefs about sleep hygiene using the Theory of Planned Behavior (TPB). Since no standardized tools exist, items were developed based on prior research and theoretical guidelines. Validity was confirmed through factor analysis and internal consistency testing.

The instrument includes 7-point Likert scales measuring:

Attitudes (6 items) - Perceptions of sleep hygiene. Higher scores indicate more favorable attitudes (score range of 6 to 42).

Subjective norms (4 items) - Perceived social expectations. Higher scores reflect stronger norms (score range of 4 to 28).

Motivation to comply (4 items) - Importance given to others' opinions (score range of 4 to 28).

Perceived control (4 items) - Confidence in maintaining good sleep habits (score range of 4 to 28).

Intention (3 items) - Readiness to adopt healthy sleep behaviors (score range of 3 to 21).

This structured approach ensures a comprehensive assessment of beliefs and behavioral influences.

Perceived stress is evaluated using the Perceived Stress Scale (PSS), which measures how stressful life situations are perceived. This self-administered questionnaire consists of 14 items, rated on a 5-point Likert scale (0 = "Never", 1 = "Almost never", 2 = "Sometimes", 3 = "Fairly often", 4 = "Very often"). The total score ranges from 0 to 56, with higher scores indicating greater perceived stress. The PSS will be used to control for stress levels during evaluation phases, especially around exam periods, when participants are expected to report higher stress levels.