CannabisNCT05160688
Changes in Cognition and Psychiatric Disorder Symptoms During Cannabis Abstinence Using a Novel Discordant Twin Design
A study testing Contingency management in people with Cannabis, run by University of Colorado, Denver at 1 site in United States.
Trial summary
This study will test whether 42 days of cannabis abstinence, compared to continued cannabis use, is associated with improvements in cognition and psychiatric disorder symptoms. Identical twins, who are concordant on cannabis use, will be experimentally-manipulated to be discordant for 42 days. Read more about this study
- Who is it for?
- Ages 31 to 47 yearsHealthy volunteers can take part
- Conditions the study is for
- Cannabis
- What is being tested?
- Contingency management
- Type of treatment
- Lifestyle or therapy programme
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 146 participants
- Where
- 1 siteUnited States
- Study dates
- 5 May 2023to 23 Mar 2026
- Phase
- Interventional
- Are there results?
- None posted in the registry
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 31 to 47 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Monozygotic (MZ) twin pair, in which both twins are willing to participate
- MZ twin pair must be concordant in their frequency of cannabis use (+/- 2 days)
- Cannabis use at least 1x per week on most weeks
- Cannabis use in the past 7 days at the baseline visit
- Positive qualitative urine toxicology at baseline for THC
- Located within the state of Colorado
Who cannot join
- 1) Discordance in the twin pairs on a significant, adverse experience, like traumatic brain injury.
Trial locations and contacts
1 site in 1 country.
About this study
This study will test whether 42 days of cannabis abstinence, compared to continued cannabis use, is associated with improvements in cognition and psychiatric disorder symptoms. Identical twins, who are concordant on cannabis use, will be experimentally-manipulated to be discordant for 42 days. Each twin, within a twin pair, will be randomly assigned to either the contingency management condition, incentive-based protocol to promote cannabis abstinence, or control condition, no changes in cannabis use requested.
Read the detailed description
The proposed project is a randomized controlled trial to compare cognition and psychiatric disorder symptoms between monozygotic (MZ) twin pairs, who are concordant on frequency of cannabis use. Each twin, within the twin pair, will be randomly assigned to either contingency management (CM), monetary incentives provided to reinforce cannabis abstinence, or control, no changes in cannabis use required or reinforced. Participants in the CM condition will receive an increasing schedule of payments at each visit reinforcing continued cannabis abstinence. All participants will receive increases in the payment schedule for attendance of each subsequent assessment. Participants will be assessed on measures of cognition including attention, memory, and processing speed as well as anxiety, depression, and ADHD symptoms. In addition, at each visit participants will complete a qualitative and quantitative drug test. The qualitative drug test will be used to determine if new cannabis use has occurred since the last visit, and will determine if the participant receives payment for abstinence. The investigators will also use previously collected genotype for each participant.
The first aim of this study is to characterize cognitive recovery, across all potential cognitive domains, using an experimental manipulation to achieve discordance between MZ twins on cannabis use. The hypothesis for the first aim is that the abstinent group will have greater improvements in memory and processing speed compared to controls. However, there will not be any group differences between the abstinent group and the control group on attention, language, and executive function performance. The second aim of the proposed project is to characterize psychiatric disorder symptoms by comparing psychiatric disorder symptom changes among the cannabis abstaining twin to their cannabis using co-twin across 42 days. The abstinent group will endorse more psychiatric symptoms during the withdrawal period (up to 14 days) but will endorse fewer psychiatric symptoms at day 28 and 42 compared to the control group. The third aim (exploratory) of the proposed project is to examine how genetic risk for psychiatric disorders interacts with environment (i.e., cannabis abstinence versus continued use) to influence cognitive functioning. The hypothesis for aim 3 is that anxiety, depression, and ADHD polygenic scores will be more strongly associated with cognitive outcomes in the control group compared to the abstinent group.
- Conditions
- Cannabis
- Being tested
- Contingency management
- Medical subject headings
- Marijuana Abuse
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Contingency managementBehavioural
Participants will be paid to abstain from cannabis use.
| Study group | Role | What they receive |
|---|---|---|
| Contingency management | Experimental | Contingency management (CM) is an incentive-based intervention providing patients with tangible rewards as reinforcement for positive behaviors like abstinence from drug use. Incentives are provided with each urine sample that is drug-free and are increased with each subsequent drug-free urine sample. Participants in the CM condition will receive increasing payments for abstinence: $30 on day 3, $45 on day 5, $60 on day 7, $75 on day 14, $90 on day 21, $105 on day 28, and $120 on day 42. Participants in both conditions also receive increasing payment for visit attendance: $10 on day 1, $15 on day 3, $20 on day 5, $25 on day 7, $30 on day 14, $35 on day 21, $45 on day 28, and $55 on day 42. At the end of the baseline visit, participants in the CM condition will sign a behavioral contract with study staff that clearly outlines expectations as well as the payment schedule. Receives: Behavioral: Contingency management |
| No intervention | No intervention | Participants in this condition will be monitored and will not receive any compensation for cannabis abstinence. |
What is being measured
The primary outcome is the main question the study is designed to answer.
Change in attention performance
Flanker Inhibitory Control and Attention Test on NIH Toolbox: Composite score of accuracy and reaction time
Measured: Change from baseline to day 42
Change in episodic memory
Picture Sequence Memory Test on NIH Toolbox: Cumulative number of correct adjacent pairs
Measured: Change from baseline to day 42
Change in working memory
List Sorting Working Memory Test on NIH Toolbox: Total items correct across all trials
Measured: Change from baseline to day 42
Change in receptive vocabulary
Picture Vocabulary Test on NIH Toolbox: Computer adaptive testing
Measured: Change from baseline to day 42
Change in reading decoding
Oral Reading Recognition Test: Number of letters and words read correctly
Measured: Change from baseline to day 42
Change in immediate memory/verbal learning
Auditory Verbal Learning Test on NIH Toolbox: Total number of words recalled
Measured: Change from baseline to day 4
Change in pattern comparison processing speed
Pattern Comparison Processing Speed Test: Total number of correct responses
Measured: Change from baseline to day 42
Change in oral symbol digit test processing speed
Oral Symbol Digit Test on NIH Toolbox: Total number of correctly identified symbols
Measured: Change from baseline to day 42
Change in attention and executive function
Dimensional Change Card Sort Test on NIH Toolbox: Composite score of accuracy and correct answers
Measured: Change from baseline to day 42
Secondary outcomes (3)
Change in anxiety symptoms
Beck Anxiety Inventory: Total score. Scores range from 0-63 and higher scores indicate higher levels of anxiety.
Measured: Change from baseline to day 42
Change in depressive symptoms
Beck Depression Inventory: Total score. Scores range from 0-63 and higher scores indicate greater levels of depression.
Measured: Change from baseline to day 42
Change in attention deficit/hyperactivity disorder symptoms
Adult Self-Report Scale: Total score. Scores range from 0-72 and higher scores indicate greater level of symptoms of attention deficit/hyperactivity disorder.
Measured: Change from baseline to day 42
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted16 Dec 2021
- Study start5 May 2023
- Primary completion23 Mar 2026
- Study completion23 Mar 2026
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for CannabisStudies of the same condition, open and under way.
- More trials run by University of Colorado, DenverThe 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
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Enrolment
- 146 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of Colorado, Denver
- Sponsor type
- University, hospital or other
- Collaborators
- University of Colorado, Boulder
- Responsible party
- Sponsor
- Investigators
- J. Megan Ross, Ph.D., Principal investigator, University of Colorado, Denver
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05160688
- Sponsor's protocol ID
- 21-4899
- Status last verified
- Aug 2026
- First submitted
- 19 Nov 2021
- Last updated
- 20 Aug 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No: In accordance with NIH data sharing policies, data produced from this project will be made available to ensure timely translation of research results to improve human health. The investigators believe there is a possibility of deductive disclosure of subjects with unusual characteristics, even though all identifiers would be removed prior to release for sharing. Thus, the investigators will make the data and associated documentation available to users only under a specific data-sharing agreement that requires: (1) a commitment to using the data only for research purposes and not to identify any individual participant; (2) a commitment to securing the data using appropriate computer technology; and (3) a commitment to destroying or returning the data after analyses are completed.
Study at a glance
From the registry record, last updated by the sponsor on 20 Aug 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Changes in Cognition and Psychiatric Disorder Symptoms During Cannabis Abstinence Using a Novel Discordant Twin Design
- ClinicalTrials.gov ID
- NCT05160688
- Acronym / sponsor ID
- 21-4899
- Conditions
- Cannabis
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 146 participants (actual)
- Lead sponsor
- University of Colorado, DenverUniversity, hospital or other
- Collaborators
- University of Colorado, Boulder
- Study start
- 5 May 2023 (actual)
- Primary completion
- 23 Mar 2026 (actual)
- Study completion
- 23 Mar 2026 (actual)
- First posted
- 16 Dec 2021 (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.
This study will test whether 42 days of cannabis abstinence, compared to continued cannabis use, is associated with improvements in cognition and psychiatric disorder symptoms. Identical twins, who are concordant on cannabis use, will be experimentally-manipulated to be discordant for 42 days. Each twin, within a twin pair, will be randomly assigned to either the contingency management condition, incentive-based protocol to promote cannabis abstinence, or control condition, no changes in cannabis use requested.
Detailed description
The proposed project is a randomized controlled trial to compare cognition and psychiatric disorder symptoms between monozygotic (MZ) twin pairs, who are concordant on frequency of cannabis use. Each twin, within the twin pair, will be randomly assigned to either contingency management (CM), monetary incentives provided to reinforce cannabis abstinence, or control, no changes in cannabis use required or reinforced. Participants in the CM condition will receive an increasing schedule of payments at each visit reinforcing continued cannabis abstinence. All participants will receive increases in the payment schedule for attendance of each subsequent assessment. Participants will be assessed on measures of cognition including attention, memory, and processing speed as well as anxiety, depression, and ADHD symptoms. In addition, at each visit participants will complete a qualitative and quantitative drug test. The qualitative drug test will be used to determine if new cannabis use has occurred since the last visit, and will determine if the participant receives payment for abstinence. The investigators will also use previously collected genotype for each participant.
The first aim of this study is to characterize cognitive recovery, across all potential cognitive domains, using an experimental manipulation to achieve discordance between MZ twins on cannabis use. The hypothesis for the first aim is that the abstinent group will have greater improvements in memory and processing speed compared to controls. However, there will not be any group differences between the abstinent group and the control group on attention, language, and executive function performance. The second aim of the proposed project is to characterize psychiatric disorder symptoms by comparing psychiatric disorder symptom changes among the cannabis abstaining twin to their cannabis using co-twin across 42 days. The abstinent group will endorse more psychiatric symptoms during the withdrawal period (up to 14 days) but will endorse fewer psychiatric symptoms at day 28 and 42 compared to the control group. The third aim (exploratory) of the proposed project is to examine how genetic risk for psychiatric disorders interacts with environment (i.e., cannabis abstinence versus continued use) to influence cognitive functioning. The hypothesis for aim 3 is that anxiety, depression, and ADHD polygenic scores will be more strongly associated with cognitive outcomes in the control group compared to the abstinent group.
Study design
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Contingency management | Experimental | Behavioral: Contingency managementContingency management (CM) is an incentive-based intervention providing patients with tangible rewards as reinforcement for positive behaviors like abstinence from drug use. Incentives are provided with each urine sample that is drug-free and are increased with each subsequent drug-free urine sample. Participants in the CM condition will receive increasing payments for abstinence: $30 on day 3, $45 on day 5, $60 on day 7, $75 on day 14, $90 on day 21, $105 on day 28, and $120 on day 42. Participants in both conditions also receive increasing payment for visit attendance: $10 on day 1, $15 on day 3, $20 on day 5, $25 on day 7, $30 on day 14, $35 on day 21, $45 on day 28, and $55 on day 42. At the end of the baseline visit, participants in the CM condition will sign a behavioral contract with study staff that clearly outlines expectations as well as the payment schedule. |
| No intervention | No intervention | –Participants in this condition will be monitored and will not receive any compensation for cannabis abstinence. |
Who may qualify
- Ages
- 31 to 47 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (6 listed)
- Monozygotic (MZ) twin pair, in which both twins are willing to participate
- MZ twin pair must be concordant in their frequency of cannabis use (+/- 2 days)
- Cannabis use at least 1x per week on most weeks
- Cannabis use in the past 7 days at the baseline visit
- Positive qualitative urine toxicology at baseline for THC
Key exclusion criteria (1 listed)
- 1) Discordance in the twin pairs on a significant, adverse experience, like traumatic brain injury.
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 |
|---|---|---|
| Contingency managementParticipants will be paid to abstain from cannabis use. | Behavioural | Contingency management |
Primary outcome
Change in attention performance
Time frame: Change from baseline to day 42
Flanker Inhibitory Control and Attention Test on NIH Toolbox: Composite score of accuracy and reaction time
Change in episodic memory
Time frame: Change from baseline to day 42
Picture Sequence Memory Test on NIH Toolbox: Cumulative number of correct adjacent pairs
Change in working memory
Time frame: Change from baseline to day 42
List Sorting Working Memory Test on NIH Toolbox: Total items correct across all trials
Change in receptive vocabulary
Time frame: Change from baseline to day 42
Picture Vocabulary Test on NIH Toolbox: Computer adaptive testing
Change in reading decoding
Time frame: Change from baseline to day 42
Oral Reading Recognition Test: Number of letters and words read correctly
Change in immediate memory/verbal learning
Time frame: Change from baseline to day 4
Auditory Verbal Learning Test on NIH Toolbox: Total number of words recalled
Change in pattern comparison processing speed
Time frame: Change from baseline to day 42
Pattern Comparison Processing Speed Test: Total number of correct responses
Change in oral symbol digit test processing speed
Time frame: Change from baseline to day 42
Oral Symbol Digit Test on NIH Toolbox: Total number of correctly identified symbols
Change in attention and executive function
Time frame: Change from baseline to day 42
Dimensional Change Card Sort Test on NIH Toolbox: Composite score of accuracy and correct answers
3 secondary outcomes
Change in anxiety symptoms
Time frame: Change from baseline to day 42
Change in depressive symptoms
Time frame: Change from baseline to day 42
Change in attention deficit/hyperactivity disorder symptoms
Time frame: Change from baseline to day 42
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 20 Aug 2026.
- Individual participant dataSharing planned: No. In accordance with NIH data sharing policies, data produced from this project will be made available to ensure timely translation of research results to improve human health. The investigators believe there is a possibility of deductive disclosure of subjects with unusual characteristics, even though all identifiers would be removed prior to release for sharing. Thus, the investigators will make the data and associated documentation available to users only under a specific data-sharing agreement that requires: (1) a commitment to using the data only for research purposes and not to identify any individual participant; (2) a commitment to securing the data using appropriate computer technology; and (3) a commitment to destroying or returning the data after analyses are completed.
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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. This study is not recruiting at the moment.
J. Megan Ross, Ph.D. principal investigator
University of Colorado, Denver
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Contingency management in people with Cannabis, run by University of Colorado, Denver at 1 site in United States.
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 1 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: finished, as of the sponsor's last update on 20 Aug 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 States. 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?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Change in attention performance (time frame: Change from baseline to day 42). The study lists 9 primary outcomes in all. 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 20 Aug 2026.