Cannabis, Schizophrenia and Reward: Self-Medication and Agonist Treatment?

In this translational research proposal, based on our formulation, we seek to confirm and expand upon data obtained in our pilot study suggesting that cannabis and the cannabinoid agonist dronabinol, given in low dose to patients with schizophrenia and co-occurring cannabis use disorder, will in fact ameliorate the brain reward circuit dysregulation in these patients and, thereby, provide evidence in support of the role of cannabis as a "self-medication" agent for them.

Study Overview

• Status: Completed
• Conditions: Schizophrenia; Dual Diagnosis; Psychotic Disorder; Cannabis Use Disorder
• Intervention / Treatment: Drug: Marijuana; Drug: Dronabinol; Drug: Placebo

Detailed Description

Substance use disorders are strikingly common in patients with schizophrenia and contribute to its morbidity and cost to society. We have proposed a neurobiological formulation suggesting that cannabis and other substance use in these patients may ameliorate a dysfunction in the brain reward circuit(thus serving a "self-medication" function), while also worsening the symptoms and course of schizophrenia.

In this translational research proposal, based on our formulation, we seek to confirm and expand upon data obtained in our pilot study suggesting that cannabis and the cannabinoid agonist dronabinol, given in low dose to patients with schizophrenia and co-occurring cannabis use disorder, will in fact ameliorate the brain reward circuit dysregulation in these patients and, thereby, provide evidence in support of the role of cannabis as a "self-medication" agent for them. Also, by also testing the full range of effects produced by dronabinol (effects on brain reward circuitry assessed with task-based function MRI and resting state connectivity), as well as on reward responsiveness, mood, craving, cognition, psychiatric and extrapyramidal symptoms), we will provide clues as to whether dronabinol should be tried in low doses as an adjunctive agent (with an antipsychotic medication) to limit cannabis use in patients with schizophrenia.

This study will involve 8 groups of 25 participants each. Groups 1-3 will have diagnoses of schizophrenia and cannabis use disorder; Group 4 will have schizophrenia only, Groups 5-7 will have cannabis use disorder only and Group 8 will be healthy control participants. Following screening and baseline neuropsychiatric testing, participants will have two tests days (T1 and T2) that will include task-based functional MRI, including assessment of resting state connectivity, and measuring a number of other parameters including reward responsiveness, mood, craving, symptoms and cognition. The assessments at T1 will be virtually the same for all groups. At T2 Groups 1-3, and Groups 5-7 will be randomly assigned to one of the following conditions prior to the assessments: receiving 15mg of dronabinol and smoking a placebo marijuana cigarette, receiving a placebo pill and smoking a real marijuana cigarette, or receiving a placebo pill and smoking a placebo marijuana cigarette. Group 4 and Group 8 will receive no drug or placebo at T2. Participants receiving drug will have safety assessments before the drug is administered, after the drug is administered but before leaving the research clinic for the day, and again a week later.

• Study Type: Interventional
• Enrollment (Actual): 263
• Phase: Phase 1

Contacts and Locations

Study Locations

• United States
  • New Hampshire
    • Lebanon, New Hampshire, United States, 03756
      • Dartmouth Hitchcock Medical Center
  • Vermont
    • Burlington, Vermont, United States, 05401
      • University of Vermont

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 55 years (Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

Groups 1-3 Participants with schizophrenia and a cannabis use disorder

1. Ages 18 - 55 years
2. Diagnosis of schizophrenia
3. Diagnosis of cannabis abuse or dependence
4. Use of cannabis within the month prior to screening
5. Willing to remain abstinent for the 14 days before the baseline assessments and throughout the two scans.
6. Psychiatrically stable
7. Treated with a stable dose of an antipsychotic medication (except clozapine) for the past month
8. Not seeking treatment for their cannabis use disorder.

Group 4 - Control participants with schizophrenia

1. Ages 18 - 55 years
2. Diagnosis of schizophrenia
3. Willing to remain abstinent as described above
4. Psychiatrically stable
5. Treated with a stable dose of an antipsychotic medication (except clozapine) for the past month

Groups 5-7 - Control participants with cannabis use disorder

1. Ages 18 - 55 years
2. Diagnosis of cannabis abuse or dependence
3. Use of cannabis within the month prior to screening
4. Willing to remain abstinent as described above
5. Not seeking treatment for their cannabis use disorder.

Group 8 - Healthy control participants

1. Ages 18 - 55 years
2. Willing to remain abstinent as described above

Exclusion criteria:

Groups 1-3 with schizophrenia and a cannabis use disorder

1. Positive symptoms of psychosis (> 4 [moderate]) on any item of the Positive and Negative Syndrome Scale psychosis subscale (once abstinent) except for the hallucination item. We will exclude for a rating > 5 for this item.
2. Cocaine/stimulant use disorder
3. Pharmacological treatment for addiction
4. Mental retardation
5. History of head injury
6. Metal objects within the body that would contraindicate and MRI
7. Pregnancy or currently nursing
8. Uncontrolled medical condition
9. Taking clozapine
10. Any condition that would contraindicate use of cannabis or dronabinol.
11. History of a seizure disorder

Group 4 - Control participants with schizophrenia

1. Positive symptoms of psychosis (> 4 [moderate]) on any item of the Positive and Negative Syndrome Scale psychosis subscale (once abstinent) except for the hallucination item. We will exclude for a rating > 5 for this item.
2. Any history of a substance use disorder other than nicotine
3. Pharmacological treatment for addiction
4. Mental retardation
5. History of head injury
6. Metal objects within the body that would contraindicate and MRI
7. Pregnancy or currently nursing
8. Uncontrolled medical condition
9. Taking clozapine

Groups 5-7 - Control participants with cannabis use disorder

1. Axis I psychiatric diagnosis other than a cannabis use disorder
2. Taking any psychotropic medication
3. Pharmacological treatment for addiction
4. Mental retardation
5. History of head injury
6. Metal objects within the body that would contraindicate and MRI
7. Pregnancy or currently nursing
8. Uncontrolled medical condition
9. History of a seizure disorder

Group 8 - Healthy control participants

1. Any Axis I psychiatric diagnosis
2. Taking any psychotropic medication
3. Pharmacological treatment for addiction
4. Mental retardation
5. History of head injury
6. Metal objects within the body that would contraindicate and MRI
7. Pregnancy or currently nursing
8. Uncontrolled medical condition
9. Current tobacco smokers

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Quadruple

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Marijuana cigarette and placebo capsule; 3-5% tetrahydrocannabinol cannabis cigarette smoked immediately prior to the second functional MRI and a placebo capsule (for dronabinol) by mouth taken approximately 2.75 hours prior to the second functional MRI.	Drug: Marijuana; Smoked plant with THC; Other Names: Cannabis
Experimental: Dronabinol and placebo cigarette; Dronabinol 15mg 3-5% by mouth taken approximately 2.75 hours prior to the second functional MRI and a placebo cigarette (for marijuana) smoked immediately prior to the second functional MRI.	Drug: Dronabinol; Capsule with THC; Other Names: Marinol
Placebo Comparator: Placebo cigarette and placebo capsule; Placebo cigarette (for marijuana) smoked immediately prior to the second functional MRI and a placebo capsule (for dronabinol) by mouth taken approximately 2.75 hours prior to the second functional MRI.	Drug: Placebo; Capsule with no active ingredient

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Brain Reward Circuit Activation on fMRI Scan	Activation of the Brain Reward Circuit (particularly the nucleus accumbens) in anticipation of monetary reward. The 'Measure' is a mean of the Fisher-Z transform of the inter-regional correlation measured for each participant between the nucleus accumbens and anterior cingulate cortex. The Fisher-transformation creates a normally distributed correlation value for statistical analyses assessing between group differences. A Fisher-Z transform of '0' represents a value of '0' for the estimated correlation, which represents no correlation in the activity time series between the regions. The values reflect strengths of functional connectivity between brain regions that can be compared between groups (e.g. Healthy controls and SCZ-CUD groups who received different study drugs). Means and standard deviations similar to healthy controls would be considered a good outcome.	3 hours
Resting State Connectivity Within the Brain Reward Circuitry	Resting state connectivity within brain reward circuitry as measured with the Fisher-transformed r value of the connectivity maps between the nucleus accumbans and other brain areas. The Fisher-transformation creates a normally distributed correlation value for statistical analyses assessing between group differences (smoked THC vs placebo; oral dronabinol vs placebo)	1 hour after smoking study drug, 3 hours after oral dronabinol

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
PANSS Positive Symptoms	Positive and Negative Symptom Scale (PANSS) Positive Symptom Mean Subscale Score at 2nd Assessment Day, range 7-49, higher = more symptoms. The outcome measure was recorded at single time of measurement. The time frame includes 3 hours after oral THC/placebo and 1 hour after smoked THC/placebo (the three-hour window is inclusive of the one-hour post smoke). Each individual smoked THC or placebo AND took oral THC or placebo.	3 hours after oral THC/placebo
PANSS Negative Symptoms	Positive and Negative Symptom Scale Negative Symptom Mean Subscale Score at 2nd Assessment Day, range 7-49, higher = more symptoms. The time frame includes 3 hours after oral THC/placebo and 1 hour after smoked THC/placebo (the three-hour window is inclusive of the one-hour post smoke). Each individual smoked THC or placebo AND took oral THC or placebo.	3 hours after oral THC/placebo
Cognitive Functioning, Verbal Learning	Cognitive functioning, verbal learning Hopkins Verbal Learning Test (HVLT-R) total raw score. Possible range of scores is 0-35, higher is better functioning. The time frame includes 4 hours after oral THC/placebo and 2 hour after smoked THC/placebo (the three-hour window is inclusive of the one-hour post smoke). Each individual smoked THC or placebo AND took oral THC or placebo.	4 hours after oral drug
Drug Experience, Anxiety	Drug experience ratings of mood and desirability, anxiety rating on a scale of 0-100, higher means more anxiety. The time frame includes 3 hours after oral THC/placebo and 1 hour after smoked THC/placebo (the three-hour window is inclusive of the one-hour post smoke). Each individual smoked THC or placebo AND took oral THC or placebo.	3 hours after taking oral drug
Drug Experience Ratings of Drug Liking	Drug experience ratings of liking rating on a scale of 0-100, higher number = more liking The time frame includes 3 hours after oral THC/placebo and 1 hour after smoked THC/placebo (the three-hour window is inclusive of the one-hour post smoke). Each individual smoked THC or placebo AND took oral THC or placebo.	3 hours after taking oral drug
Cognitive Function, CPT-IP 2 Digit	Cognitive function, CPT-IP 2 digit measure of Attention. The Continuous Performance Test-Identical Pairs version (CPT-IP)80 assessed attention with range of 1-5, hirer scores indicating better function The outcome measure was recorded at single time of measurement. The time frame includes 4 hours after oral THC/placebo and 2 hour after smoked THC/placebo (the three-hour window is inclusive of the one-hour post smoke). Each individual smoked THC or placebo AND took oral THC or placebo.	4 hours after oral drug

Collaborators and Investigators

• Sponsor: Dartmouth-Hitchcock Medical Center
• Collaborators: Harvard Medical School (HMS and HSDM); National Institute on Drug Abuse (NIDA); Massachusetts General Hospital; Columbia University; Massachusetts Institute of Technology; University of Vermont; Nathan Kline Institute for Psychiatric Research
• Investigators: Principal Investigator: Mary F Brunette, MD, Dartmouth College

Study record dates

Study Major Dates

• Study Start: July 1, 2014
• Primary Completion (Actual): September 18, 2021
• Study Completion (Actual): September 18, 2021

Study Registration Dates

• First Submitted: October 15, 2013
• First Submitted That Met QC Criteria: October 16, 2013
• First Posted (Estimated): October 17, 2013

Study Record Updates

• Last Update Posted (Estimated): December 9, 2025
• Last Update Submitted That Met QC Criteria: November 18, 2025
• Last Verified: October 1, 2025

More Information

Terms related to this study

• Keywords: Schizophrenia; Substance Abuse; Dronabinol; Dual Diagnosis; Cannabis Use Disorder
• Additional Relevant MeSH Terms: Schizophrenia Spectrum and Other Psychotic Disorders; Mental Disorders; Chemically-Induced Disorders; Schizophrenia; Psychotic Disorders; Substance-Related Disorders; Organic Chemicals; Hydrocarbons; Terpenes; Cannabinoids; Dronabinol; nabiximols
• Other Study ID Numbers: D14061; 1R01DA034699-01A1 (U.S. NIH Grant/Contract)

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No