Effect of Extended Cannabis Abstinence on PTSD Symptoms

Study Overview
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Brief Summary
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This will be a 12-week randomized trial. Outpatients and patients from the Mood and Anxiety program at the Centre for Addiction and Mental Health (CAMH) with a current diagnosis of post-traumatic stressed disorder (PTSD) and cannabis-use disorder (CUD) will be randomized to receive individual motivational interviewing therapy and contingency management (n = 12) or individual motivational interviewing therapy alone (control group, n = 12) after enrolment.

Official Title
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Effect of Extended Cannabis Abstinence on PTSD Symptoms

Conditions
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PTSD, Cannabis Use, Cognitive Symptom, Comorbidities and Coexisting Conditions

Intervention / Treatment
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* Behavioral: Contingency-management
* Other: Enhanced usual care


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Subjects aged between 18 and 55 years (from both sexes [or genders]); Diagnosed with CUD (moderate or severe) according to the Structured Clinical Interview for DSM-IV (SCID) (mode of cannabis consumption can be inhalation or ingestion); Diagnosis of current (past 30 days) PTSD, using the CAPS-5 on screening; On antidepressant medication(s) for at least 1 month (to ensure safety and homogeneity as PTSD treatment of our population); Be able to provide written informed consent; and Be able to communicate in English. Exclusion Criteria: diagnosed with a severe or unstable medical illness that precludes safe participation in the study as per the study physician; diagnosed with schizophrenia, schizoaffective disorder, or bipolar disorder or current acute psychosis or mania based on DSM-5 criteria; current suicidality risk as indicated by the Columbia Suicide Severity Rating Scale (C-SSRS) with concurrence after the study physician's evaluation if the response to C-SSRS questions 1 or 2 is yes 34; and have pain interfering with normal function as reported by the 12-Item Short Form Survey (SF-12) (moderate or higher interference).

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 55 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Other
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Contingency management group<br>Randomized to receive individual motivational interviewing therapy and contingency management | Behavioral: Contingency-management<br>* In addition to structured assessments at baseline, four, eight and twelve months, subjects randomized to the contingency-management group will receive a contingent bonus if the participants show successful abstinence at the end of weeks 4, 8 and 12.<br>Other: Enhanced usual care<br>* Subjects will receive structured, quantitative assessments at baseline, four, eight and twelve weeks.<br>|
| Other: Control group<br>Randomized to receive individual motivational interviewing therapy alone | Other: Enhanced usual care<br>* Subjects will receive structured, quantitative assessments at baseline, four, eight and twelve weeks.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Severity of PTSD symptoms, as measured with the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5) at week 4 | Changes in CAPS-5 during the study phase between the group that achieved abstinence and the group that did not. In addition, we will record changes in each PTSD symptom category, which will all be part of the larger trial analysis. | Week 0-4 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Changes in cognitive function, as measured with various Cambridge Automated Neuropsychological Test Automated Battery (CANTAB) cognitive tests | Changes between abstainers and non-abstainers on cognitive testing during the study phase. | Week 0-4 |