Effects of Darkness Retreat: a Pilot Study

Effect of Darkness Retreat on Worry and Rumination in a Non-clinical Population: a Pilot Study

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.

Study Overview

• Status: Recruiting
• Conditions: Study Protocol Feasibility; Non Clinical Anxiety; Non Clinical Worry; Non Clinical Rumination
• Intervention / Treatment: Other: Darkness Retreat - Several Days of Seclusion in Complete Darkness

Detailed Description

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.

• Study Type: Interventional
• Enrollment (Estimated): 30
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Jarosław M Michałowski, Professor; Phone Number: +48 694 441 722; Email: jmichalowski@swps.edu.pl
• Study Contact Backup: Name: Katarzyna Sanna, PhD; Phone Number: +48601363388; Email: ksanna@swps.edu.pl

Study Locations

• Poland
  • Poznan, Poland
    • Recruiting
    • SWPS University of Social Sciences and Humanities
    • Contact: Jarosław M Michałowski, Prof.; Email: jmichalowski@swps.edu.pl
  • Wielkopolska
    • Poznan, Wielkopolska, Poland, 61-719
      • Recruiting
      • Poznań Laboratory of Affective Neuroscience, Institute of Psychology, SWPS University, Warsaw, Poland
      • Contact: Jarosław M. Michałowski, PhD; Phone Number: +48 692 981 911; Email: jmichalowski@swps.edu.pl

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

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).

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Low-frequency monitoring; Participants assigned to the low-frequency monitoring arm will receive one structured (full) psychological consultation per day throughout the three-day darkness retreat. Consultations will follow a standardized interview protocol focusing on emotional state, safety assessment, and participant well-being. Each session will be conducted without direct visual or physical contact, taking place through a wall separating the participant's cabin from the adjacent monitoring room. Consultations will coincide with meal delivery to minimize disruption of the retreat experience.	Other: Darkness Retreat - Several Days of Seclusion in Complete Darkness; The intervention is a voluntary darkness retreat involving three days and three nights of continuous seclusion in a completely dark cabin, with no access to external light sources or electronic devices. During the retreat, participants are consulted about their well-being through a standardized interview protocol, with consultation frequency determined by their assigned group. Participants in both groups will be equipped with WHOOP wristbands - devices monitoring physiological activity. These wristbands will serve a dual purpose: From a research perspective, they will provide access to biological data- circadian rhythm patterns and heart rate variability, offering deeper insights into the physiological processes accompanying the darkness retreat experience. From a safety perspective, they will enable real-time monitoring of participants' condition, supporting one of the main goals of the pilot study: ensuring participant safety while assessing the feasibility of the procedure.
Experimental: High-frequency monitoring; Participants assigned to the high-frequency monitoring arm will receive three psychological consultations per day during the three-day darkness retreat: one full structured interview and two shorter check-ins. All consultations will follow a predefined protocol to ensure consistency, with the full interview assessing emotional state, safety, and well-being, and the shorter check-ins focusing on brief status updates and safety screening. As in the low-frequency condition, there will be no direct visual or physical contact; all interactions will take place through a wall separating the participant's cabin from the monitoring room. Consultations will be scheduled approximately every three hours during waking hours to allow for more detailed and time-sensitive data collection	Other: Darkness Retreat - Several Days of Seclusion in Complete Darkness; The intervention is a voluntary darkness retreat involving three days and three nights of continuous seclusion in a completely dark cabin, with no access to external light sources or electronic devices. During the retreat, participants are consulted about their well-being through a standardized interview protocol, with consultation frequency determined by their assigned group. Participants in both groups will be equipped with WHOOP wristbands - devices monitoring physiological activity. These wristbands will serve a dual purpose: From a research perspective, they will provide access to biological data- circadian rhythm patterns and heart rate variability, offering deeper insights into the physiological processes accompanying the darkness retreat experience. From a safety perspective, they will enable real-time monitoring of participants' condition, supporting one of the main goals of the pilot study: ensuring participant safety while assessing the feasibility of the procedure.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Study Protocol Feasibility	Feasibility will be assessed based on participant recruitment and retention rates, adherence to the intervention schedule, completeness of data collection at all time points, and occurrence of any adverse events during the darkness retreat.	From recruitment start until completion of the six-month follow-up.
Penn State Worry Questionnaire Score Change	The total sum score of the Polish version of the Penn State Worry Questionnaire.	Time point 1: Just prior to the intervention. Time point 2: Immediately after the intervention. Time point 3: Six months after the previous measurement (time point 2).

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
CESD-R Score Change	The total sum score of the Polish version of the Center for Epidemiologic Studies Depression Scale Revised.	Time point 1: Just prior to the intervention. Time point 2: Immediately after the intervention. Time point 3: Six months after the previous measurement (time point 2).
State-Trait Anxiety Inventory Score Change	The total sum score of the Polish version of the State-Trait Anxiety Inventory.	Time point 1: Just prior to the intervention. Time point 2: Immediately after the intervention. Time point 3: Six months after the previous measurement (time point 2).
Abbreviated Five Facet Mindfulness Questionnaire Score Change	The total sum score of the Polish version of the Abbreviated Five Facet Mindfulness Questionnaire.	Time point 1: Just prior to the intervention. Time point 2: Immediately after the intervention. Time point 3: Six months after the previous measurement (time point 2).
Ruminative Thoughts Questionnaire Score Change	The total sum score of the Polish version of the Ruminative Thoughts Questionnaire.	Time point 1: Just prior to the intervention. Time point 2: Immediately after f the intervention. Time point 3: Six months after the previous measurement (time point 2).
Meaning in Life Questionnaire Score Change	The total sum scores of the Polish version of the Meaning in Life Questionnaire.	Time point 1: Just prior to the intervention. Time point 2: Immediately after the intervention. Time point 3: Six months after the previous measurement (time point 2).
Self-Compassion Scale - Short Form Score Change	The total sum scores of the Polish version of the Self-Compassion Scale - Short Form.	Time point 1: Just prior to the intervention. Time point 2: Immediately after the intervention. Time point 3: Six months after the previous measurement (time point 2).
Post-Traumatic Growth Score Change	The total sum score of the Polish version of the Post-Traumatic Growth.	Time point 2: Immediately after the intervention. Time point 3: Six months after the previous measurement (time point 2).
Go / no - go Test Change	The total change of the completion time of the test.	Time point 1: Just prior to the intervention. Time point 2: Immediately after the intervention. Time point 3: Six months after the previous measurement (time point 2).

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Personal Development Initiative Scale score change	The total sum score of the Polish version of the Personal Development Initiative Scale.	Time point 1: Just prior to the intervention. Time point 2: Immediately after the intervention. Time point 3: Six months after the previous measurement (time point 2).
Client Satisfaction Questionnaire score change	The total sum score of the Polish version Client Satisfaction Questionnaire.	Time point 2: Immediately after the intervention. Time point 3: Six months after the previous measurement (time point 2).
Credibility/Expectations Questionnaire score change	The total sum score of the Polish version of Credibility/Expectations Questionnaire	Time point 1: Just prior to the intervention. Time point 2: Immediately after the intervention. Time point 3: Six months after the previous measurement (time point 2).
Negative Effects of Intervention Questionnaire score change	The total sum score of the Polish version of the Negative Effects of Intervention Questionnaire.	Time point 1: Just prior to the intervention. Time point 2: Immediately after the intervention. Time point 3: Six months after the previous measurement (time point 2).

Collaborators and Investigators

• Sponsor: University of Social Sciences and Humanities, Warsaw
• Collaborators: Within Properties

Publications and helpful links

General Publications

• Soláriková, P., Bartolen, I. (2025). Effects of chamber restricted environmental stimulation therapy on state mindfulness, physiological regulation and emotional experience in young adults: Exploring variations by resting heart rate variability. Acta psychologica, 253, 104697. https://doi.org/10.1016/j.actpsy.2025.104697
• Hruby, H., Schmidt, S., Feinstein, J. S., Wittmann, M. (2024). Induction of altered states of consciousness during Floatation-REST is associated with the dissolution of body boundaries and the distortion of subjective time. Scientific Reports, 14, 9316. https://doi.org/10.1038/s41598-024-59642-y
• Flux, M. C., Fine, T. H., Poplin, T., Al Zoubi, O., Schoenhals, W. A., Schettler, J., Refai, H. H., Naegele, J., Wohlrab, C., Yeh, H.-W., Lowry, C. A., Levine, J. C., Smith, R., Khalsa, S. S., Feinstein, J. S. (2022). Exploring the acute cardiovascular effects of Floatation-REST. Frontiers in Neuroscience, 16. https://doi.org/10.3389/fnins.2022.995594
• Feinstein, J. S., Khalsa, S. S., Yeh, H., Al Zoubi, O., Arevian, A. C., Wohlrab, C., Pantino, M. K., Cartmell, L. J., Simmons, W. K., Stein, M. B., Paulus, M. P. (2018). The elicitation of relaxation and interoceptive awareness using floatation therapy in individuals with high anxiety sensitivity. Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, 3(6), 555-562. https://doi.org/10.1016/j.bpsc.2018.02.005

Study record dates

Study Major Dates

• Study Start (Actual): October 16, 2025
• Primary Completion (Estimated): October 1, 2026
• Study Completion (Estimated): November 1, 2026

Study Registration Dates

• First Submitted: December 16, 2025
• First Submitted That Met QC Criteria: February 19, 2026
• First Posted (Actual): February 24, 2026

Study Record Updates

• Last Update Posted (Actual): February 24, 2026
• Last Update Submitted That Met QC Criteria: February 19, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: Anxiety; Mindfulness; sensory deprivation; darkness retreat; protocol feasibility
• Additional Relevant MeSH Terms: Mental Disorders; Anxiety Disorders
• Other Study ID Numbers: SWPS_Retreat_RCT_1

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Anonymized data from all enrolled participants will be publicly available in the project's OSF repository.
• IPD Sharing Time Frame: IPD and supporting documents will be available as soon as research results are published.
• IPD Sharing Access Criteria: IPD and supporting documents will be publicly available.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; ICF

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No