Cannabis IntoxicationENDURANCENCT07471347
Exploring The Effect Of Cannabidiol On Cannabis Tolerance Using A Novel Vaporiser Device In Heavy Users (Stage 1)
A study testing delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) in people with Cannabis Intoxication, run by King's College London at 1 site in United Kingdom.
Trial summary
Cannabis contains delta-9-tetrahydrocannabinol (THC), which causes intoxication. People who use cannabis frequently often develop tolerance, meaning they need to use more THC to feel the same effects. Read more about this study
- Who is it for?
- Ages 18 to 45 years
- Conditions the study is for
- Cannabis Intoxication
- What is being tested?
- delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD)
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 10 participants
- Where
- 1 siteUnited Kingdom
- Study dates
- Mar 2026to Dec 2026
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 45 years
- All sexes
- No healthy volunteers
- Adult
Who may be able to join
- Adults, between 18 and 45 years old
- Heavy and frequent cannabis user: using 7-14 grams of high potency cannabis per week over the past month, and using cannabis on at least 5 days per week over the past month
- Positive urine drug screen (UDS) for cannabis
- Willing to abstain from cannabis use for 4 hours before any experimental session.
- Willing to eat two non-vegan full-fat yoghurts to aid drug absorption
- Providing written informed consent.
Who cannot join
- Dependent use of alcohol or illicit drugs (apart from cannabis or tobacco/nicotine)
- Not able to provide a UDS which is negative for illicit drugs (apart from cannabis)
- Not able to provide a negative alcohol breath test
- Personal or family history (first-degree) of psychosis or mania
- Currently prescribed antidepressant, mood-stabilising, antipsychotic or stimulant medication, or regular medication for a significant medical condition (e.g. antihypertensives, anticonvulsants, anticoagulants, or immunosuppressants)
- Diagnosis of a major medical or psychiatric illness that the study doctor considers inappropriate for the purposes of this study
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- Female participants who are pregnant or mothers who are lactating
- Not willing to use an adequate form of contraception for the duration of the study
- Participant in another experimental medicine study or clinical trial within the past three months.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
United Kingdom1 site
King's Clinical Research Facility
London
Edward Chesney, +4420 7836 5454
About this study
Official title: Exploring The Effect Of Cannabidiol On Cannabis Tolerance Using A Novel Vaporiser Device In Heavy Users: A Randomised Placebo-Controlled Experimental Study (Stage 1)
Cannabis contains delta-9-tetrahydrocannabinol (THC), which causes intoxication. People who use cannabis frequently often develop tolerance, meaning they need to use more THC to feel the same effects. Cannabidiol (CBD) is another compound found in cannabis that is not intoxicating and may influence how THC affects the body and brain.
This study will examine whether taking CBD changes how much THC heavy cannabis users consume to reach their usual level of intoxication. The study will also develop a new laboratory method that allows participants to safely and gradually self-administer THC using a vaporiser, similar to how cannabis is used in real-world settings.
Read more
The study will include around 30 adults who use cannabis heavily. In the first stage, participants will take part in pilot sessions to help refine the THC administration procedure. In the second stage, participants will attend two study sessions and receive a single oral dose of CBD or placebo, in a random order. After this, they will inhale THC using a vaporiser and decide when to stop based on how intoxicated they feel.
Researchers will measure how much THC is used, along with mood, mental health symptoms, thinking abilities, physical measures such as heart rate and blood pressure, and blood levels of THC and CBD. The results will help improve understanding of cannabis tolerance and whether CBD alters responses to THC in heavy cannabis users.
Read the detailed description
Cannabis produces its intoxicating effects mainly through delta-9-tetrahydrocannabinol (THC). People who use cannabis frequently often develop tolerance, meaning they need to consume larger amounts of THC to achieve their usual level of intoxication. Cannabidiol (CBD) is another cannabinoid found in cannabis that does not cause intoxication and may alter how THC affects the body and brain. However, its effects on cannabis tolerance in heavy users are not well understood.
This study aims to develop a controlled laboratory method for measuring cannabis tolerance and to investigate whether CBD changes how much THC heavy cannabis users consume. The study is conducted in two stages and will recruit approximately 30 adult heavy cannabis users who do not have a history of psychotic or major medical disorders.
In Stage One, participants will take part in pilot sessions to establish a safe and reliable method of THC administration using a handheld vaporiser. Participants will self-administer THC in small doses at regular intervals and decide when they have reached their usual and maximum tolerated levels of intoxication. These pilot sessions will be used to refine the timing, dosing, and outcome measures used in the main experiment.
In Stage Two, participants will complete two experimental sessions in a double-blind, randomised, placebo-controlled, crossover design. In each session, participants will receive a single oral dose of CBD (1000 mg) or a matching placebo, followed three hours later by THC administration using the vaporiser. The order of CBD and placebo will be randomised, and sessions will be separated by a washout period.
During each experimental session, participants will self-titrate THC intake until they reach their typical desired level of intoxication and may continue until they reach their maximum tolerated level. Cannabis tolerance will be assessed by measuring the amount of THC consumed, based on changes in vaporiser cartridge weight and the number of inhalations required to reach these intoxication levels.
Additional outcomes include subjective drug effects, mood, psychotic-like symptoms, cognitive performance, speech measures, physical observations (such as heart rate and blood pressure), and blood levels of THC, CBD, and related biomarkers. Safety will be closely monitored throughout all sessions by trained medical staff.
The findings from this study will help establish a novel experimental model of cannabis tolerance and improve understanding of how CBD influences responses to THC in heavy cannabis users.
- Conditions
- Cannabis Intoxication
- Being tested
- delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD)
- Keywords
- Cannabis, THC, Delta-9-tetrahydrocannabinol
- Medical subject headings
- Marijuana Abuse
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD)Drug
Vida T400:C20 Blueberry Cookies Medical Cannabis Cartridge (400mg delta-9-tetrahydrocannabinol and 20mg cannabidiol per cartridge)
| Study group | Role | What they receive |
|---|---|---|
| Delta-9-tetrahydrocannabinol/Cannabidiol | Experimental | Delta-9-tetrahydrocannabinol/Cannabidiol (vaporised; self-administered by the participant, titrated to individual tolerability) Receives: Drug: delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) |
What is being measured
The primary outcome is the main question the study is designed to answer.
Cannabis tolerance
Change in THC cartridge weight
Measured: From initiation of use until the participant reaches their desired level of intoxication (self-titrated), assessed up to 4 hours.
Secondary outcomes (10)
Cannabis tolerance (maximum)
Change in THC cartridge weight
Measured: From initiation of use until the participant reaches their maximum tolerated level of intoxication (self-titrated), assessed up to 4 hours.
Drug effects questionnaire (DEQ)
Five-item questionnaire on drug effects
Measured: Baseline; The timepoint at which the participant reaches their desired level of intoxication (self-titrated); The timepoint at which the participant reaches their maximum tolerated level of intoxication (self-titrated), assessed up to 4 hours.
Visual analogue scales
- Relaxed/Anxious
- Sad/Happy
- Not paranoid/Paranoid
- Thinking clearly/confused
- Tired/Energetic
Measured: Baseline; The timepoint at which the participant reaches their desired level of intoxication (self-titrated); The timepoint at which the participant reaches their maximum tolerated level of intoxication (self-titrated), assessed up to 4 hours.
Observer Rated Cannabis Intoxication Scale (ORCIS)
A Likert scale to rate the participant's level of intoxication
Measured: Baseline; The timepoint at which the participant reaches their desired level of intoxication (self-titrated); The timepoint at which the participant reaches their maximum tolerated level of intoxication (self-titrated), assessed up to 4 hours.
Cannabis withdrawal Scale (CWS)
A 19-item self-report questionnaire designed to assess the severity of cannabis withdrawal symptoms
Measured: Baseline; The timepoint at which the participant reaches their desired level of intoxication (self-titrated); The timepoint at which the participant reaches their maximum tolerated level of intoxication (self-titrated), assessed up to 4 hours.
Marijuana Craving Questionnaire-Short Form
A brief assessment tool used to measure craving for cannabis
Measured: Baseline; The timepoint at which the participant reaches their desired level of intoxication (self-titrated); The timepoint at which the participant reaches their maximum tolerated level of intoxication (self-titrated), assessed up to 4 hours.
Positive and negative symptom scale
An investigator-rated measure of psychotic symptoms.
Measured: Baseline; The timepoint at which the participant reaches their desired level of intoxication (self-titrated); The timepoint at which the participant reaches their maximum tolerated level of intoxication (self-titrated), assessed up to 4 hours.
Psychotomimetic States Inventory
A 48-item questionnaire that was developed for use in drug studies to measure psychotic-like experiences
Measured: Baseline; The timepoint at which the participant reaches their desired level of intoxication (self-titrated); The timepoint at which the participant reaches their maximum tolerated level of intoxication (self-titrated), assessed up to 4 hours.
Digit symbol substitution test
Measured: Baseline; The timepoint at which the participant reaches their desired level of intoxication (self-titrated); The timepoint at which the participant reaches their maximum tolerated level of intoxication (self-titrated), assessed up to 4 hours.
Forward and reverse digit span
Assessment of working memory: Forward Digit Span is the maximum number of digits the participant can correctly repeat in the same order, and Reverse Digit Span is the maximum number of digits the participant can correctly repeat in reverse order.
Measured: Baseline; The timepoint at which the participant reaches their desired level of intoxication (self-titrated); The timepoint at which the participant reaches their maximum tolerated level of intoxication (self-titrated), assessed up to 4 hours.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted13 Mar 2026
- Study startMar 2026 (estimated)
- Primary completionDec 2026 (estimated)
- Study completionDec 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Cannabis IntoxicationStudies of the same condition, open and under way.
- More trials run by King's College LondonThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Basic science
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Enrolment
- 10 participants (estimated)
Sponsor and investigators
- Lead sponsor
- King's College London
- Sponsor type
- University, hospital or other
- Collaborators
- South London and Maudsley NHS Foundation Trust
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07471347
- Sponsor's protocol ID
- R&D2025/050
- Acronym
- ENDURANCE
- Status last verified
- Jan 2026
- First submitted
- 30 Jan 2026
- Last updated
- 13 Mar 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 13 Mar 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Exploring The Effect Of Cannabidiol On Cannabis Tolerance Using A Novel Vaporiser Device In Heavy Users: A Randomised Placebo-Controlled Experimental Study (Stage 1)
- ClinicalTrials.gov ID
- NCT07471347
- Acronym / sponsor ID
- ENDURANCE / R&D2025/050
- Conditions
- Cannabis Intoxication
- Keywords
- Cannabis, THC, Delta-9-tetrahydrocannabinol
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 10 participants (estimated)
- Lead sponsor
- King's College LondonUniversity, hospital or other
- Collaborators
- South London and Maudsley NHS Foundation Trust
- Study start
- Mar 2026 (estimated)
- Primary completion
- Dec 2026 (estimated)
- Study completion
- Dec 2026 (estimated)
- First posted
- 13 Mar 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Cannabis contains delta-9-tetrahydrocannabinol (THC), which causes intoxication. People who use cannabis frequently often develop tolerance, meaning they need to use more THC to feel the same effects. Cannabidiol (CBD) is another compound found in cannabis that is not intoxicating and may influence how THC affects the body and brain.
This study will examine whether taking CBD changes how much THC heavy cannabis users consume to reach their usual level of intoxication. The study will also develop a new laboratory method that allows participants to safely and gradually self-administer THC using a vaporiser, similar to how cannabis is used in real-world settings.
The study will include around 30 adults who use cannabis heavily. In the first stage, participants will take part in pilot sessions to help refine the THC administration procedure. In the second stage, participants will attend two study sessions and receive a single oral dose of CBD or placebo, in a random order. After this, they will inhale THC using a vaporiser and decide when to stop based on how intoxicated they feel.
Researchers will measure how much THC is used, along with mood, mental health symptoms, thinking abilities, physical measures such as heart rate and blood pressure, and blood levels of THC and CBD. The results will help improve understanding of cannabis tolerance and whether CBD alters responses to THC in heavy cannabis users.
Detailed description
Cannabis produces its intoxicating effects mainly through delta-9-tetrahydrocannabinol (THC). People who use cannabis frequently often develop tolerance, meaning they need to consume larger amounts of THC to achieve their usual level of intoxication. Cannabidiol (CBD) is another cannabinoid found in cannabis that does not cause intoxication and may alter how THC affects the body and brain. However, its effects on cannabis tolerance in heavy users are not well understood.
This study aims to develop a controlled laboratory method for measuring cannabis tolerance and to investigate whether CBD changes how much THC heavy cannabis users consume. The study is conducted in two stages and will recruit approximately 30 adult heavy cannabis users who do not have a history of psychotic or major medical disorders.
In Stage One, participants will take part in pilot sessions to establish a safe and reliable method of THC administration using a handheld vaporiser. Participants will self-administer THC in small doses at regular intervals and decide when they have reached their usual and maximum tolerated levels of intoxication. These pilot sessions will be used to refine the timing, dosing, and outcome measures used in the main experiment.
In Stage Two, participants will complete two experimental sessions in a double-blind, randomised, placebo-controlled, crossover design. In each session, participants will receive a single oral dose of CBD (1000 mg) or a matching placebo, followed three hours later by THC administration using the vaporiser. The order of CBD and placebo will be randomised, and sessions will be separated by a washout period.
During each experimental session, participants will self-titrate THC intake until they reach their typical desired level of intoxication and may continue until they reach their maximum tolerated level. Cannabis tolerance will be assessed by measuring the amount of THC consumed, based on changes in vaporiser cartridge weight and the number of inhalations required to reach these intoxication levels.
Additional outcomes include subjective drug effects, mood, psychotic-like symptoms, cognitive performance, speech measures, physical observations (such as heart rate and blood pressure), and blood levels of THC, CBD, and related biomarkers. Safety will be closely monitored throughout all sessions by trained medical staff.
The findings from this study will help establish a novel experimental model of cannabis tolerance and improve understanding of how CBD influences responses to THC in heavy cannabis users.
Study design
- Primary purpose
- Basic science
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| Delta-9-tetrahydrocannabinol/Cannabidiol | Experimental | Drug: delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD)Delta-9-tetrahydrocannabinol/Cannabidiol (vaporised; self-administered by the participant, titrated to individual tolerability) |
Who may qualify
- Ages
- 18 to 45 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult
Key inclusion criteria (6 listed)
- Adults, between 18 and 45 years old
- Heavy and frequent cannabis user: using 7-14 grams of high potency cannabis per week over the past month, and using cannabis on at least 5 days per week over the past month
- Positive urine drug screen (UDS) for cannabis
- Willing to abstain from cannabis use for 4 hours before any experimental session.
- Willing to eat two non-vegan full-fat yoghurts to aid drug absorption
Key exclusion criteria (9 listed)
- Dependent use of alcohol or illicit drugs (apart from cannabis or tobacco/nicotine)
- Not able to provide a UDS which is negative for illicit drugs (apart from cannabis)
- Not able to provide a negative alcohol breath test
- Personal or family history (first-degree) of psychosis or mania
- Currently prescribed antidepressant, mood-stabilising, antipsychotic or stimulant medication, or regular medication for a significant medical condition (e.g. antihypertensives, anticonvulsants, anticoagulants, or immunosuppressants)
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD)Vida T400:C20 Blueberry Cookies Medical Cannabis Cartridge (400mg delta-9-tetrahydrocannabinol and 20mg cannabidiol per cartridge) | Drug | Delta-9-tetrahydrocannabinol/Cannabidiol |
Primary outcome
Cannabis tolerance
Time frame: From initiation of use until the participant reaches their desired level of intoxication (self-titrated), assessed up to 4 hours.
Change in THC cartridge weight
10 secondary outcomes
Cannabis tolerance (maximum)
Time frame: From initiation of use until the participant reaches their maximum tolerated level of intoxication (self-titrated), assessed up to 4 hours.
Drug effects questionnaire (DEQ)
Time frame: Baseline; The timepoint at which the participant reaches their desired level of intoxication (self-titrated); The timepoint at which the participant reaches their maximum tolerated level of intoxication (self-titrated), assessed up to 4 hours.
Visual analogue scales
Time frame: Baseline; The timepoint at which the participant reaches their desired level of intoxication (self-titrated); The timepoint at which the participant reaches their maximum tolerated level of intoxication (self-titrated), assessed up to 4 hours.
Observer Rated Cannabis Intoxication Scale (ORCIS)
Time frame: Baseline; The timepoint at which the participant reaches their desired level of intoxication (self-titrated); The timepoint at which the participant reaches their maximum tolerated level of intoxication (self-titrated), assessed up to 4 hours.
Cannabis withdrawal Scale (CWS)
Time frame: Baseline; The timepoint at which the participant reaches their desired level of intoxication (self-titrated); The timepoint at which the participant reaches their maximum tolerated level of intoxication (self-titrated), assessed up to 4 hours.
Marijuana Craving Questionnaire-Short Form
Time frame: Baseline; The timepoint at which the participant reaches their desired level of intoxication (self-titrated); The timepoint at which the participant reaches their maximum tolerated level of intoxication (self-titrated), assessed up to 4 hours.
Positive and negative symptom scale
Time frame: Baseline; The timepoint at which the participant reaches their desired level of intoxication (self-titrated); The timepoint at which the participant reaches their maximum tolerated level of intoxication (self-titrated), assessed up to 4 hours.
Psychotomimetic States Inventory
Time frame: Baseline; The timepoint at which the participant reaches their desired level of intoxication (self-titrated); The timepoint at which the participant reaches their maximum tolerated level of intoxication (self-titrated), assessed up to 4 hours.
Digit symbol substitution test
Time frame: Baseline; The timepoint at which the participant reaches their desired level of intoxication (self-titrated); The timepoint at which the participant reaches their maximum tolerated level of intoxication (self-titrated), assessed up to 4 hours.
Forward and reverse digit span
Time frame: Baseline; The timepoint at which the participant reaches their desired level of intoxication (self-titrated); The timepoint at which the participant reaches their maximum tolerated level of intoxication (self-titrated), assessed up to 4 hours.
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 13 Mar 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) in people with Cannabis Intoxication, run by King's College London at 1 site in United Kingdom.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 6 inclusion and 9 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 13 Mar 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United Kingdom. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Edward Chesney, MRCPsych PhD (+4420 7836 5454, kingscrf@kcl.ac.uk), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Cannabis tolerance (time frame: From initiation of use until the participant reaches their desired level of intoxication (self-titrated), assessed up to 4 hours.). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 13 Mar 2026.