An observational study in HIV Prevention, Substance Use and Mental Health, sponsored by Institute of HIV Research and Innovation Foundation, Thailand. Recruiting at 1 site in Thailand. Open to male participants aged 18 Years and older, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-04-06.
Sponsored by Institute of HIV Research and Innovation Foundation, Thailand · Observational
This study evaluates the pre-implementation phase of a host-led harm reduction model for men who have sex with men (MSM) engaging in chemsex in Bangkok, Thailand, focusing on understanding harms, contexts, and needs to develop a tailored intervention.
HAMMOCK is a cross-sectional mixed-methods study designed to explore chemsex practices among MSM, including both hosts and guests, as well as key stakeholders such as CSOs, hospital staff, and police.
The study aims to:
2,238 studies on the registry are indexed under Substance-Related Disorders; 409 are open to participants now.
This study's planned enrollment of 76 is below the median of 251 across 299 observational studies indexed under Substance-Related Disorders.
Browse Substance-Related Disorders studies →Institute of HIV Research and Innovation Foundation, Thailand is the lead sponsor of 13 studies on the registry; 8 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Recruit chemsex party hosts, chemsex party guests, representatives from the CSOs, government hospital, police organization G1: Chemsex party hosts 1. Have ever hosted a chemsex party at least 2 times in the past 6 months.
G2: Chemsex party guests
1. Have ever attended a chemsex party at least 2 times in the past 6 months.
G3: CSOs 1. Currently working in a CSO 3. Hold a role or perform a duty related to chemsex-related incidents or drug use for more than 3 months.
G4: Government hospitals
G5: Police officers
1. Currently working in a police organization. 3. Hold a role or perform the duty related to chemsex-related incidents or drug use for more than 3 months.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Specific by group:
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants (chemsex party hosts, guests, CSO staff, hospital staff, and police officers) will participate in a mixed-method study consisting of two phases (Exploration and Preparation) to assess harms related to chemsex and to develop and refine a novel harm reduction model for private chemsex party settings.
Behavioral: Self-administered questionnaire assessment · Behavioral: Semi-structured in-depth interviews (IDIs) · Behavioral: Development and refinement of harm reduction model
Participants (chemsex party hosts and guests) will complete structured self-administered questionnaires to assess: * Substance use patterns and related harms * Sexual health risks (e.g., condom use, HIV/STI testing, PrEP/ART adherence) * Mental health status using validated tools: * Patient Health Questionnaire-9 (PHQ-9) * Generalized Anxiety Disorder-7 (GAD-7) * Socio-legal harms including stigma and discrimination
All stakeholders will participate in semi-structured in-depth interviews: * Exploration phase: guided by EPIS framework * Preparation phase: guided by * Theoretical Domains Framework (TDF) (hosts \& guests) * Consolidated Framework for Implementation Research (CFIR) (organizational stakeholders) The interviews aim to: * Identify harms associated with chemsex * Explore current practices and contexts * Identify barriers and facilitators * Inform development and refinement of a harm reduction model
A novel four-pronged harm reduction model will be developed and refined based on quantitative and qualitative findings. Domains include: * Substance use harm reduction * Sexual health harm reduction * Mental health harm reduction * Socio-legal harm reduction
Substance use-related harm assessed by self-administered questionnaire
Substance-related harms will be assessed using a structured self-administered questionnaire. The assessment includes: * Patterns of substance use (snorting, injecting, ingesting, anal insertion) * Frequency of use * Physical harms (e.g., injection-related injuries, overdose) * Psychological harms (e.g., substance dependence) This is a descriptive assessment; no composite scale score is generated.
Time frame: Baseline (during Exploration phase, prior to model development)
Sexual health risk behaviors assessed by self-administered questionnaire
Sexual health risks will be assessed using a structured questionnaire including: * Number of sexual partners * Condom use * HIV/STI testing history * Self-reported HIV status * Pre-exposure prophylaxis (PrEP) use and adherence * Antiretroviral therapy (ART) adherence among participants living with HIV This is a descriptive assessment; no composite scale score is generated.
Time frame: Baseline (during Exploration phase, prior to model development)
Depression severity assessed by Patient Health Questionnaire-9 (PHQ-9)
Depression will be assessed using the Patient Health Questionnaire-9 (PHQ-9): * Score range: 0 to 27 * Interpretation: * 0-4: Minimal depression * 5-9: Mild * 10-14: Moderate * 15-19: Moderately severe * 20-27: Severe Higher scores indicate worse depression severity
Time frame: Baseline (during Exploration phase, prior to model development)
Anxiety severity assessed by Generalized Anxiety Disorder-7 (GAD-7)
Anxiety will be measured using the Generalized Anxiety Disorder-7 (GAD-7): * Score range: 0 to 21 * Interpretation: * 0-4: Minimal * 5-9: Mild * 10-14: Moderate * 15-21: Severe Higher scores indicate worse anxiety
Time frame: Baseline (during Exploration phase, prior to model development)
Perceived stigma and socio-legal harm assessed by structured questionnaire
Socio-legal harms will be assessed using a structured questionnaire adapted from the CLYMAX study, including: * Internalized stigma related to chemsex * Perceived discrimination (family, workplace, social) * Legal risks and experiences This is a descriptive assessment; no composite scale score is generated.
Time frame: Baseline (during Exploration phase, prior to model development)
Started Feb 2025 (actual). Primary completion is estimated for Feb 2027, 24 months after the start.
Of 122 non-industry observational studies under Substance-Related Disorders, half reached primary completion within 36 months of starting (the median), counting those still running; a quarter within 18 and three quarters within 56. This study's planned 24 months is below that.
Counting every sponsor, half of 133 studies reached it within 36 months; a quarter within 18 and three quarters within 56.
How these figures are worked out, and which studies are left out of them.
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Institute of HIV Research and Innovation Foundation, Thailand