The primary goal of this pilot study is to test the feasibility and safety of a research protocol for a voluntary darkness retreat.

The study will also allow for a preliminary examination of the psychological effects of the retreat. The investigators will investigate whether participants experience changes in their well-being and ruminative style, whether these changes persist over time, and if these effects are moderated by individual characteristics such as readiness for change or subjective evaluation of the experience as well as frequency of participants' monitoring.

Participants will be randomly assigned to one of two experimental groups, both of which will spend 3 days and 3 nights in seclusion. These groups will differ only in the frequency of psychological monitoring during the retreat, allowing us to compare the effectiveness and safety of each protocol.

The aim of the pilot study is to test a research protocol designed to assess the psychological effects of several days of voluntary darkness retreat. The primary objective of the pilot is to examine whether the protocol is feasible, implementable, and safe under real-world conditions when working with a non-clinical population. Our sample will consist of 30 psychologically healthy students aged 30-50 with higher levels of trait anxiety and worry. Participants will be randomly assigned to one of the two conditions: (1) Low-frequency monitoring: one structured psychological consultation per day (one full psychological consultation per day) (2) High-frequency monitoring: three consultations per day (one full consultation + two shorter check-ins).

The trial will also provide preliminary data on whether participating in a darkness retreat is associated with any changes in well-being and ruminative thought style. The investigators will examine if changes are observed in the levels of anxiety, ruminative style, worry, mindfulness, and a sense of meaning in life, if those changes differentiate accordingly to the monitoring frequency (high monitoring vs. low monitoring), and if those changes persist over time (at the 6-month follow-up).

The study uses a 2 × 3 mixed factorial design with two intervention arms (low-frequency vs. high-frequency monitoring) and three measurement time points: T1 - just prior to the intervention, T2 - immediately after the intervention, and T3 - six-month follow-up. The primary intervention lasts three days and three nights. All primary and secondary outcomes are assessed using self-administered online questionnaires in Polish. Each primary outcome measure will be analyzed using 2 (arms) × 3 (time points) ANOVA models to test for the short- and long-term intervention effects. Additional analyses will use standard NHST procedures (e.g., t-tests and correlation coefficients) with a conventional significance level of α = .05.

During the study, participants will not be informed that its primary aim is to compare two variants of the psychological monitoring protocol. This information will be withheld to minimize the risk of expectancy effects. To ensure the highest ethical standards, a debriefing procedure will be carried out after the study has been completed.

Participants will be recruited from university/postgraduate students through a two-stage process.

Stage I. Individuals expressing interest in participation will be asked to confirm that they are not currently engaged in psychotherapy or coaching, are not taking psychotropic medication, and are in generally good physical health. The following individuals will be excluded from the study: those diagnosed with an acute or chronic somatic illness (e.g., cardiovascular disease); psychiatric or neurological disorders (e.g., depression, addiction, bipolar disorder, schizophrenia, epilepsy, stroke, severe brain injury, Parkinson's disease, Alzheimer's disease or other forms of dementia); those exhibiting active suicidal tendencies with a plan or intent; those taking psychotropic medication; engaged in psychotherapy or coaching; and pregnant individuals.

Preliminary verification of these criteria will be carried out using a screening questionnaire containing demographic questions and items regarding psychotherapy/coaching, use of psychoactive medication, somatic health, suicidal tendencies, pregnancy, and confirmation of a history of diagnoses in the categories of psychotic disorders, eating disorders, obsessive-compulsive disorder, substance use disorders, bipolar disorder, along with the following questionnaires:

PSWQ: Inclusion criteria based on the PSWQ (Penn State Worry Questionnaire, range 16-80, higher scores indicating worse functioning):

Participants must obtain a total score between 40 and 80. (40-59 = moderate level of worry/anxiety) (60-80 = high level of worry/anxiety)

In cases where participants fall within the high range, if clinical levels of worry are identified during the clinical interview, they will be excluded from participation.

PAtient Health Questionnaire-9 (PHQ-9, range 0-27, higher scores indicating worse functioning): Individuals scoring above 10 will be considered at elevated risk for depression, and those scoring 20 or higher will not be invited to the clinical interview.

Generalized Anxiety Disorder-7 (GAD-7, range 0-21, higher scores indicating worse functioning): Individuals scoring 7 or higher will be classified as having elevated generalized anxiety symptoms, and those scoring 15 or higher will be excluded from further participation.

Alcohol Use Disorders Identification Test (AUDIT, range 0-40, higher scores indicating worse functioning): Individuals scoring above 8 will be considered at elevated risk for problematic drinking, and those scoring 22 or higher will not be invited to the clinical interview.

Drug Use Disorders Identification Test (DUDIT, range 0-44, higher scores indicating worse functioning): Individuals scoring above 4 will be classified as at elevated risk for substance use, and those scoring 7 or higher will be excluded.

The questionnaire will also include the following measures, which will not be used for automatic exclusion but will indicate the need for further evaluation during the clinical interview if the following thresholds are met:

DSM-5 - Panic Disorder (range 0-40, higher scores indicating worse functioning): score ≥ 26 DSM-5 - Social Anxiety Disorder (range 0-40, higher scores indicating worse functioning): score ≥ 26 DSM-5 - Post-Traumatic Stress Disorder (range 0-44, higher scores indicating worse functioning): score > 22

Only individuals who are not excluded based on the above criteria will be invited to the next stage.

Stage II. Candidates meeting the preliminary criteria will be invited to an online clinical interview with a psychologist. Approximately one week before the scheduled interview, participants will receive via email a link to the Personality Beliefs Questionnaire (PBQ; Zawadzki et al., 2017), that would help in a more in-depth assessment of psychological functioning during the actual meeting. In order to exclude clinical cases, the psychologist will use the structured clinical interview M.I.N.I. (Mini International Neuropsychiatric Interview)

Participants who complete the psychological interview-regardless of their final qualification for the study-will receive a compensation of approximately 200 ZŁ in shopping vouchers (50EUR).

Anonymized data from all enrolled participants will be publicly available in the project's OSF repository.

IPD and supporting documents will be available as soon as research results are published.

IPD and supporting documents will be publicly available.

During the study, participants will not be informed that its primary aim is to compare two variants of the psychological monitoring protocol-more frequent versus less frequent-in terms of their impact on worry levels and overall psychological well-being. This information will be withheld to minimize the risk of expectancy effects, which could distort participants' responses and reduce the reliability of the collected data.

Due to the nature of the study, it is not possible to obtain valid results while fully informing participants about this aspect in advance. Disclosing this information during participation could influence how they experience the retreat and report their well-being.

To ensure the highest ethical standards, a debriefing procedure will be carried out after the study has been completed (i.e., after the follow-up assessment and prior to the anonymization of data). Participants will be fully informed about the actual aim of the study and the methodological approach used.