Neurocognitive and Clinical Effects of a Culturally Adapted Subliminal Auditory Intervention Integrating Mindfulness and Existential Components on Suicidal Ideation in Adolescents

The aim of this study is to evaluate the clinical and neurocognitive effects of a culturally adapted subliminal auditory intervention, based on mindfulness and existential principles, on suicidal ideation and related psychological variables in Iranian adolescents.

A cluster-randomized, parallel-group, double-blind, phase 2 clinical trial conducted on 600 adolescents with suicidal ideation in psychological clinics across Iran. Clinics are the unit of randomization, and the random allocation sequence is generated using computer-based random numbers in R.

This cluster-randomized study is conducted in psychological clinics across Iran. Clinics are allocated to intervention or control groups. The intervention group receives a culturally adapted subliminal audio file based on mindfulness and existential elements in 16 sessions; the control group receives a matched neutral file. Data are collected at pre-test, post-test, and 3-month follow-up. The trial is parallel and double-blind, and analyses use coded data.

Inclusion criteria: Adolescents with suicidal ideation who have been screened in participating clinics. Exclusion criteria: Severe psychiatric disorders; cognitive limitations preventing participation; acute suicidal

Intervention group: A culturally adapted subliminal audio file based on mindfulness and existential elements is delivered over 16 sessions, containing subliminal messages intended to reduce suicidal ideation and improve psychological variables. Control group: A neutral audio file matched in auditory features, without any subliminal or therapeutic content, used only to control expectancy and listening conditions.

suicidal ideation; rumination; anhedonia; mental health

1. Randomization Method: This study employs cluster randomization, in which psychological clinics across Iran are considered clusters and are randomly assigned to either the Intervention group or the Control group. To maintain balance between the groups, block randomization at the cluster level will be applied. 2. Unit of Randomization: The unit of randomization is the psychological clinic. To prevent contamination between groups, all eligible adolescents within each clinic will be assigned to the same study arm. 3. Stratification Layers (if applied): This study will use stratified cluster randomization. The stratification layers include: Geographical region (north, south, east, west, central) Clinic size (low-caseload, medium-caseload, high-caseload) 4. Randomization Tools: The random allocation sequence will be generated using standard tools, including: R statistical software for computer-generated random numbers Variable block sizes to avoid predictability A researcher independent from participant recruitment will perform the randomization procedure. 5. Generation of the Random Allocation Sequence: Clinics will first be stratified based on predefined layers. A list of random numbers will then be generated using statistical software, and clinics will be assigned to blocks of 4 to 6 clusters. The allocation sequence will be generated by an independent researcher to prevent bias. 6.Allocation Concealment: To ensure proper allocation concealment: The randomization sequence will be placed in opaque, sealed, sequentially numbered envelopes. These envelopes will only be opened after the completion of baseline assessment at each clinic. The recruitment team will not have access to the allocation sequence. This method prevents prior knowledge of group assignment and reduces selection bias.

1. Participants: Participants are and will remain unaware of their group allocation (intervention or control). Both groups receive an audio file that is indistinguishable in terms of listening experience; therefore, participants remain blinded throughout the entire study. 2. Outcome Assessors: Outcome assessors do not and will not have access to group allocation. All data are provided to them in anonymized, coded format with no indicators of group assignment. 3. Data Collectors: Data collectors do not have access to the randomization sequence and receive all information only through participant codes. They remain blinded throughout the data collection process. 4. Principal Investigator: The principal investigator remains blinded during data collection and outcome assessment and will gain access to group allocation only after the completion of all analyses. Blinding of the principal investigator is maintained during the analysis phase. 5. Clinical Staff: Clinical staff who deliver the audio files to participants are unaware of the file type and the assigned group. Therefore, these staff members also remain blinded during the study procedures. 6. Data Safety and Monitoring Committee (DSMC): The DSMC has access only to coded, anonymized datasets. Unblinding occurs solely in the event of a serious safety concern. 7. Data Analysts and Manuscript Writers: Data analysts and manuscript authors work with fully de-identified datasets and remain blinded to group allocation until the completion of statistical analyses. Unblinding is performed only after the analysis is finalized.

Title of documents: De-identified participant data, including questionnaire results (primary and secondary outcomes) Individual participant data will be shared after removal of all identifiable and personal information. Only data related to primary and secondary outcomes, including questionnaire scores at pre-test, post-test, and 3-month follow-up, will be accessible. Raw identifiable data, audio files, or any confidential information will not be shared.

Data access will begin 6 months after publication of the study results and will remain available for 5 years following publication.

Data will be available only to researchers affiliated with accredited academic or research institutions, upon formal request and review by the study’s research committee.

Conditions for data use: Data may be used only for scientific and research purposes. A defined and approved research proposal is required. Commercial use, redistribution, or sharing with third parties is prohibited. Any attempt to identify participants or restore personal information is strictly forbidden. Access will be granted only after signing a responsible data-use agreement.

Investigator using the information below: Name and position: Dr. Khatereh Arbabi (Principal Investigator) Address: No. 33, Rasoulian Lane, Zabeti Street, Heravi, Tehran, Iran Email: arbabikhatere@gmail.com Phone: +98 912 224 3889 Requests will be accepted only via email or formal written communication and data access will be granted after review by the Principal Investigator and approval of the research committee.

Process for Requesting and Receiving Data: Submit a formal request to the principal investigator’s email, including a brief description of the proposed research. Initial review of the request by the principal investigator (within approximately 2 weeks). Submission of the full proposal, a data-use commitment form, and documentation of institutional affiliation. Final review and approval by the research committee (within approximately 2–4 weeks). Upon approval, de-identified data will be shared with the applicant through a secure transfer method.Estimated total time for the process: 4–6 weeks.