title: Is cannabis use associated with less opioid use among people who inject drugs?
abstract: BACKGROUND
  Clinical, experimental, and ethnographic research suggests that cannabis may be used to help manage pain. Ethnographic research has revealed that some people are using cannabis to temper their illicit opioid use. We seek to learn if there is an association between cannabis use and the frequency of nonmedical opioid use among people who inject drugs (PWID).
  
  
  METHODS
  PWID were recruited using targeted sampling methods in Los Angeles and San Francisco, California, 2011-2013. We limited analysis to people who used opioids in past 30 days (N=653).
  
  
  METHODS
  number of times used any opioids non-medically in past 30 days. Explanatory variable: any cannabis use past 30 days.
  
  
  METHODS
  multivariable linear regression with a log-transformed outcome variable.
  
  
  RESULTS
  About half reported cannabis use in the past 30 days. The mean and median number of times using opioids in past 30 days were significantly lower for people who used cannabis than those who did not use cannabis (mean: 58.3 vs. 76.4 times; median: 30 vs 60 times, respectively; p<0.003). In multivariable analysis, people who used cannabis used opioids less often than those who did not use cannabis (Beta: -0.346; 95% confidence interval: -0.575, -0.116; p<0.003).
  
  
  CONCLUSIONS
  There is a statistical association between recent cannabis use and lower frequency of nonmedical opioid use among PWID. This may suggest that PWID use cannabis to reduce their pain and/or nonmedical use of opioids. However, more research, including prospective longitudinal studies, is needed to determine the validity of these findings.
authors.affiliation: RTI International, 351 California Street Suite 500, San Francisco, CA 94104, USA. Electronic address: akral@rti.org.
authors.forename: Alex H
authors.initials: AH
authors.lastname: Kral
authors.affiliation: RTI International, 351 California Street Suite 500, San Francisco, CA 94104, USA.
authors.forename: Lynn
authors.initials: L
authors.lastname: Wenger
authors.affiliation: RTI International, 351 California Street Suite 500, San Francisco, CA 94104, USA.
authors.forename: Scott P
authors.initials: SP
authors.lastname: Novak
authors.affiliation: Department of Preventive Medicine, Institute for Prevention Research, Keck School of Medicine, University of Southern California, Soto Street Building, SSB, 2001 N. Soto Street, 3rd Floor, Rm 302R, MC 9239, Los Angeles, CA 90032-3628, USA. Electronic address: rbluthen@usc.edu.
authors.forename: Daniel
authors.initials: D
authors.lastname: Chu
authors.affiliation: Department of Psychiatry, University of Colorado, Denver School of Medicine, 1557 Ogden St., Denver, CO 80218, USA. Electronic address: Karen.Corsi@ucdenver.edu.
authors.forename: Karen F
authors.initials: KF
authors.lastname: Corsi
authors.affiliation: Department of Family and Community Medicine, University of California, San Francisco, CA, USA.
authors.forename: Diana
authors.initials: D
authors.lastname: Coffa
authors.affiliation: Department of Family and Community Medicine, University of California, San Francisco, CA, USA; Department of Psychiatry, University of California, San Francisco, CA, USA.
authors.forename: Brad
authors.initials: B
authors.lastname: Shapiro
authors.affiliation: Department of Preventive Medicine, Institute for Prevention Research, Keck School of Medicine, University of Southern California, Soto Street Building, SSB, 2001 N. Soto Street, 3rd Floor, Rm 302R, MC 9239, Los Angeles, CA 90032-3628, USA.
authors.forename: Ricky N
authors.initials: RN
authors.lastname: Bluthenthal
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D015141:Los Angeles / Q000453:epidemiology; D008297:Male; D008385:Marijuana Smoking / Q000453:epidemiology*; D008875:Middle Aged; D009293:Opioid-Related Disorders / Q000453:epidemiology*; D011446:Prospective Studies; D012495:San Francisco / Q000453:epidemiology; D015819:Substance Abuse, Intravenous / Q000453:epidemiology*; D055815:Young Adult
keywords: Cannabis; Epidemiology; Injection drug use; Opioids; PWID