Brain Mechanisms Supporting Cannabis-induced Pain Relief

Chronic low back pain is a common and disabling condition that affects millions of people in the United States. Many people with chronic low back pain do not get enough relief from current treatments. Cannabis may help reduce pain, but researchers do not fully understand how it affects the brain in people with chronic pain. The purpose of this study is to examine how inhaled cannabis changes brain activity and reduces pain in people with chronic low back pain. Results from this study may help researchers better understand how cannabis works for pain and support the development of improved pain treatments.

Study Overview

• Status: Recruiting
• Conditions: Lower Back Pain; Back Pain; Sciatica; Degenerative Disc Disease; Lumbar Radiculopathy; Chronic Low-back Pain (cLBP); Chronic Low Back and Leg Pain
• Intervention / Treatment: Drug: Active Cannabis; Drug: Placebo Cannabis

Detailed Description

Chronic low back pain is one of the most common causes of pain and disability in adults. Unfortunately, treatments that can directly reduce chronic low back pain remain limited. Cannabis has shown promise for pain relief, but researchers do not yet fully understand how it affects the brain or reduces pain in people with chronic pain.

The purpose of this study is to examine how inhaled (vaporized, not smoked) cannabis affects pain responses and brain activity in adults with chronic low back pain. Researchers will compare the effects of cannabis containing tetrahydrocannabinol (THC) to a placebo cannabis containing 0% THC.

This study involves one visit to the Keck Center for Functional MRI at UC San Diego. Participants will complete screening procedures, questionnaires, and pain testing using heat stimulation applied to the calf. Participants will be trained to rate their pain intensity and unpleasantness. A straight leg raise maneuver will also be performed to assess low back pain and any pain radiating down the leg.

Participants will inhale either THC-containing cannabis or placebo cannabis (no THC) using a vaporization device under study staff supervision. Brain imaging, heat pain testing, leg raise assessments, and pain ratings will be collected before and after cannabis administration to evaluate changes in pain processing and brain activity. Researchers will also assess self-reported pain, mood, sleep, stress, and cannabis-related effects using standardized questionnaires.

This study may improve understanding of how cannabis influences the brain and pain systems in people with chronic low back pain, and findings may help support the development of improved treatments for chronic pain.

• Study Type: Interventional
• Enrollment (Estimated): 100
• Phase: Early Phase 1

Contacts and Locations

• Study Contact: Name: Madelynn Meredith, BS; Phone Number: 619-431-1850; Email: mameredith@health.ucsd.edu
• Study Contact Backup: Name: Yasmeen Esshaki, MA; Phone Number: 619-786-0375; Email: yesshaki@health.ucsd.edu

Study Locations

• United States
  • California
    • La Jolla, California, United States, 92093
      • Recruiting
      • Center for Functional MRI - W.M.Keck Building
      • Principal Investigator: Fadel Zeidan, PhD
      • Contact: Madelynn Meredith, BS; Phone Number: 619-431-1850; Email: mameredith@health.ucsd.edu
      • Contact: Yasmeen Esshaki, MA; Phone Number: 619-786-0375; Email: yesshaki@health.ucsd.edu

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 21 years to 65 years (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Between 21-65 years old
• Currently 30 days cannabis free
• Lower back pain for three months or more
• Are not taking opioids
• If female and of a child bearing potential age, are not pregnant or nursing mothers
• Do not have mental or neurological conditions inhibiting sensory/motor functions
• Do not have a lifetime history of dependence on cannabis
• Do not have a lifetime history of DSM-IV schizophrenia, bipolar disorder, panic disorder, or psychosis
• Prior THC-containing cannabis experience within the past two years
• Agrees not to use cannabis outside of the study during participation in the study
• Agrees not to use opioids or barbiturates during participation in the study
• Agrees not to drive a motor vehicle within 4 hours following last use of inhaled cannabis during participation in the study

Exclusion Criteria:

• Active pulmonary disease
• Allergy or past adverse effects or negative past experiences from cannabis
• Positive urine drug test for THC, barbiturates, opioids, oxycodone, or methadone
• Any significant illness, including cardiovascular disease, diabetes, renal and liver disease.
• Any current or history of an immunocompromising disease or condition (such as lupus, psoriasis, multiple sclerosis, etc.)
• Any current or history of neurologic conditions, including Parkinson disease, dementia, cognitive impairment, history of seizure disorder, and history of traumatic brain injury/head injury
• Any current major psychiatric illness, such as bipolar disorder, major depression, psychosis, substance use disorder, or schizophrenia
• Any current or history of suicidal ideation or attempt
• Overt sensitivity to thermal stimulation
• Resting blood pressure > 140/90
• Resting heart rate > 100 beats/minute
• Prisoner
• Institutionalized
• Claustrophobia
• MRI contraindications
• Participation in any new (within 2 weeks prior or any time after enrollment) pain management procedures during the study period
• Known history of vasovagal fainting, syncope, or severe adverse reactions associated with blood draws or needle procedures

Study Plan

How is the study designed?

Design Details

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

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Active THC; Participants will be administered 400mg of vaporized cannabis (5.1%) before pain testing and fMRI.	Drug: Active Cannabis; 400 mg of vaporized and inhaled active cannabis (5.1%)
Placebo Comparator: Placebo THC; Participants will be administered 400mg of vaporized cannabis (<.1%) before pain testing and fMRI.	Drug: Placebo Cannabis; 400 mg of vaporized and inhaled placebo cannabis (<.1%); Other Names: Non-Active cannabis

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Cerebral Blood Flow (CBF)	Changes in brain blood flow and oxygen levels will be measured using non-invasive MRI-based brain imaging methods. These scans will assess how much blood is reaching brain tissue and how oxygen levels in the brain change over time.	All data will be collected at the single study session (Day 1).

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Pain Ratings	Pain ratings will be assessed in response to noxious heat stimulation. Pain intensity and pain unpleasantness will be measured using a 0-10 Visual Analog Scale (VAS), where 0 indicates "no pain" and 10 indicates "most intense imaginable pain" or "most unpleasant imaginable pain." Higher scores indicate greater pain intensity or unpleasantness. Subjective response to cannabis will be assessed using a 0-10 Numeric Rating Scale (NRS), with higher scores indicating greater subjective effects.	All data will be collected at the single study session (Day 1).

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Neurochemical Metabolites	We will use a specialized, non-invasive brain scan called proton magnetic resonance spectroscopy (1H-MRS) to measure certain brain chemicals linked to pain processing, including glutamate, GABA, and myo-inositol. The scan uses radiofrequency signals (sim	All data will be collected at the single study session (Day 1).
Respiration Rate	Changes in breathing rate may be associated with pain relief and improved well-being. Breathing rate will be monitored continuously in real time to ensure accurate data collection.	All data will be collected at the single study session (Day 1).
THC Concentrations	THC concentrations will be measured to evaluate the relationship between THC levels and pain relief.	All data will be collected at the single study session (Day 1).

Collaborators and Investigators

• Sponsor: University of California, San Diego

Study record dates

Study Major Dates

• Study Start (Actual): May 7, 2021
• Primary Completion (Estimated): January 15, 2027
• Study Completion (Estimated): March 15, 2027

Study Registration Dates

• First Submitted: July 7, 2021
• First Submitted That Met QC Criteria: July 19, 2021
• First Posted (Actual): July 29, 2021

Study Record Updates

• Last Update Posted (Actual): June 3, 2026
• Last Update Submitted That Met QC Criteria: May 30, 2026
• Last Verified: January 1, 2026

More Information

Terms related to this study

• Keywords: chronic low back pain; Cannabis; THC; Vaporized cannabis
• Additional Relevant MeSH Terms: Pain; Neurologic Manifestations; Bone Diseases; Musculoskeletal Diseases; Nervous System Diseases; Mental Disorders; Neuromuscular Diseases; Peripheral Nervous System Diseases; Spinal Diseases; Substance-Related Disorders; Chemically-Induced Disorders; Neuralgia; Mononeuropathies; Sciatic Neuropathy; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Back Pain; Radiculopathy; Marijuana Abuse; Low Back Pain; Intervertebral Disc Degeneration; Sciatica
• Other Study ID Numbers: 200011

Drug and device information, study documents

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