Light Therapy for University Students

The Bergen Insomnia Scale (BIS) is a short scale on sleep habits consisting of six items pertaining to sleep onset, maintenance, early morning wakening, restorative sleep, daytime functioning, and sleep satisfaction. Responses indicate how often sleep problems, according to the six items, are experienced during the last month on an 8-point scale (0-7 days per week) with a range between 0 and 42, where a higher score suggests more sleep problems.

The Pittsburgh Sleep Quality Index (PSQI) consists of 19 self-rated items about sleep habits during the last month. The questions are categorised into seven components, rated from 0 to 3, evaluating sleep duration, quality, and latency as well as habitual sleep efficiency, sleep disturbances, usage of sleep medication, and daytime dysfunction. A global PSQI score, ranging from 0 to 21, is calculated by summarising the seven components' scores, where a higher global score indicates worse sleep quality and a score above five suggests poor sleep quality.

Wrist-worn actigraphy devices (model GT3X+ ActiSleep) were used to objectively measure sleep. Sleep parameters were calculated using the Cole-Kripke sleep algorithm in the ActiLife 6 data analysis software. Parameter measured: Total time in bed, measured as minutes.

Wrist-worn actigraphy devices (model GT3X+ ActiSleep) were used to objectively measure sleep. Sleep parameters were calculated using the Cole-Kripke sleep algorithm in the ActiLife 6 data analysis software. Parameter measured: Total sleep time, measured as minutes.

Wrist-worn actigraphy devices (model GT3X+ ActiSleep) were used to objectively measure sleep. Sleep parameters were calculated using the Cole-Kripke sleep algorithm in the ActiLife 6 data analysis software. Parameter measured: Sleep latency, measured as minutes.

Wrist-worn actigraphy devices (model GT3X+ ActiSleep) were used to objectively measure sleep. Sleep parameters were calculated using the Cole-Kripke sleep algorithm in the ActiLife 6 data analysis software. Parameter measured: Wake after sleep onset, measured as minutes.

Wrist-worn actigraphy devices (model GT3X+ ActiSleep) were used to objectively measure sleep. Sleep parameters were calculated using the Cole-Kripke sleep algorithm in the ActiLife 6 data analysis software. Parameter measured: Number of awakenings, measured as number of awakenings per sleep period.

Wrist-worn actigraphy devices (model GT3X+ ActiSleep) were used to objectively measure sleep. Sleep parameters were calculated using the Cole-Kripke sleep algorithm in the ActiLife 6 data analysis software. Parameter measured: Sleep fragmentation index, measured as percentage.

Wrist-worn actigraphy devices (model GT3X+ ActiSleep) were used to objectively measure sleep. Sleep parameters were calculated using the Cole-Kripke sleep algorithm in the ActiLife 6 data analysis software. Parameter measured: Sleep movement index, measured as events per hour.

Wrist-worn actigraphy devices (model GT3X+ ActiSleep) were used to objectively measure sleep. Sleep parameters were calculated using the Cole-Kripke sleep algorithm in the ActiLife 6 data analysis software. Parameter measured: Sleep efficiency, measured as percentage.

The Center for Epidemiological Studies Depression Scale (CES-D) is a 20 item self-report instrument, designed to measure common symptoms of depression that have occurred over the past week such as poor appetite, hopelessness, pessimism, and fatigue. Response options range from 0 to 3 for each item. Scores range from 0 to 60, with high scores indicating greater depressive symptoms.

General Anxiety Disorder (GAD-7) is a shorter version of the original GAD-13 item scale designed to measure anxiety. Each of the seven questions is rated on a 4-point Likert scale based on symptom frequency. The total score is calculated by summing the scores for all seven items, thus scores range from 0 to 21, with higer score meaning more anxiety. Cut-points are as follows: 0-4: Minimal anxiety, 5-9: Mild anxiety, 10-14: Moderate anxiety, and 15-21: Severe anxiety. A score of 10 or greater is often used as a clinical cut-off point.

The reduced Horne & Östberg Morningness-Eveningness Questionnaire (rMEQ) is a self-report questionnaire is one of the most widely used questionnaire to measure chronotype. The rMEQ consists of 5 questions that assess an individual's preference for morning or evening activities. Based on results from the scoring, individuals can be categorized as: Morning Types: Prefer morning activities; Evening Types: Prefer evening activities or Intermediate Types: Have no strong preference.

The Epworth Sleepiness Scale (ESS) is widely used in sleep research and clinical settings and consists of 8 questions (each with 4 answering possibilities) about sleepiness. measure a person's likelihood of dozing off during various daily activities. ESS provides a score ranging from 0 to 24, with higher scores indicating excessive daytime sleepiness. In general ESS scores can be interpreted as follows: 0-5 Lower Normal Daytime Sleepiness; 6-10 Higher Normal Daytime Sleepiness; 11-12 Mild Excessive Daytime Sleepiness; 13-15 Moderate Excessive Daytime Sleepiness; and 16-24 Severe Excessive Daytime Sleepiness.

Three neuropsychological tests were used to measure cognitive performance: Operation Span (Ospan) is a cognitive task designed to measure working memory capacity by requiring participants to remember sequences of letters while simultaneously solving simple math problems. This dual-task approach assesses how well individuals can manage their memory resources under distraction.

Three neuropsychological tests were used to measure cognitive performance: Digit span forward is a cognitive task where a person listens to a sequence of numbers and then repeats them back in the same order. This task primarily measures short-term auditory memory and is commonly used in psychological assessments to evaluate working memory capacity.

Three neuropsychological tests were used to measure cognitive performance: Digit span backward is a cognitive task that measures short-term memory by requiring participants to recall a sequence of numbers in reverse order. This task is more challenging than recalling the numbers in the original order, as it involves both storage and manipulation of the information.