Medical cannabis use among patients with chronic pain in an interdisciplinary pain rehabilitation program: Characterization and treatment outcomes.

INTRODUCTION: Cannabis is increasingly being used in the treatment of chronic pain. However, there is a lack of available research in the population of patients with chronic pain who are using cannabis. The current study examines clinical and treatment characteristics for patients who are admitted to a 3-week outpatient interdisciplinary chronic pain rehabilitation program.

METHOD: Participants (N=48) included patients with a positive urine drug screen for 9-carboxy-tetrahydrocannabinol (THC(+); n=24) and a matched comparison sample of patients with a negative screen (THC(-); n=24). Participants were matched for age, gender, race, education, and current prescription opioid use. Measures of pain, functioning, and quality of life were completed at admission and discharge. Medical chart review was conducted to assess medication and substance use history.

RESULTS: Participants with a positive screen for THC were more likely to report a past history of illicit substance use, alcohol abuse, and current tobacco use. Cannabis use was not associated with a significantly lower morphine equivalence level for participants using prescription opioids (n=14). Both groups of participants reported significant improvement in pain severity, pain interference, depressive symptoms, and pain catastrophizing. There were no group- or treatment-related differences in these outcome variables.

DISCUSSION: Results provide preliminary evidence that patients with chronic pain using cannabis may benefit from an interdisciplinary chronic pain program. Patients with chronic pain using cannabis may be at higher risk for substance-related negative outcomes, although more research is needed to understand this relationship.