Elsevier

Drug and Alcohol Dependence

Volume 153, 1 August 2015, Pages 236-241
Drug and Alcohol Dependence

Is cannabis use associated with less opioid use among people who inject drugs?

https://doi.org/10.1016/j.drugalcdep.2015.05.014Get rights and content

Highlights

  • People who inject drugs (PWID) were recruited using targeted sampling in Los Angeles and San Francisco, CA.

  • About one-half of PWID reported cannabis use in the past 30 days.

  • PWID who use cannabis used opioids less often than those who did not use cannabis.

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). Outcome variable: number of times used any opioids non-medically in past 30 days. Explanatory variable: any cannabis use past 30 days. Statistics: 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.

Introduction

The therapeutic applications of cannabis were first documented in the oldest known pharmacopeia, written by the Emperor of China, Shen Nung in 2737 BC, where it was recommended for over a wide variety of ailments, from gout to parasitic infections (Li, 1974). Since that time, there has been a stream of medical claims that cannabis eases limb-muscle spasms, is an effective analgesic and has antianxiety and antiemetic properties (Baker et al., 2003), Cannabis was part of the American pharmacopeia for much of the 19th and early 20th centuries, until the US federal government began restricting its use in the late 1930s (Bostwick, 2012), In 1970, the US Congress categorized cannabis as a Schedule I drug under the Controlled Substances Act, declaring it to have high abuse potential and no medical value, thereby rendering its use illegal (Cohen, 2010).

The past two decades has seen an increase in debate about the use of cannabis for medicinal purposes, with California becoming the first U.S. state to authorize medicinal cannabis in 1996 (O’Connell and Bou-Matar, 2007). To date, twenty-three states and the District of Columbia have passed laws that allow adult use of medical cannabis (Portal Labs, 2014). Additionally, as of February, 2014, four states – Alaska, Colorado, Oregon, Washington – and the District of Columbia, have legalized possession, manufacture and sale of cannabis for people 21 years of age and older to use recreationally (Merica, 2014).

There is a growing body of literature documenting the therapeutic benefits of cannabis (Bostwick, 2014, Grotenhermen and Muller-Vahl, 2012, Kalant, 2014, Lucas, 2012, Walsh et al., 2013). Reports of improved appetite and reduction in muscle pain, nausea, anxiety, depression and paresthesia have been associated with cannabis use among people with HIV (Woolridge et al., 2005). Cannabis use for pain relief is also common among people living with chronic non-cancer pain (Degenhardt et al., 2014). In addition to pain relief, individuals who use cannabis for therapeutic reasons report effective symptom relief for anxiety and sleep disturbances (Walsh et al., 2013). Cannabis may also act to relieve inflammation and has been found to have a useful place in the treatment of rheumatic diseases (Kalant, 2014). Multiple review articles have systematically documented the therapeutic potential of cannabis as treatment for nausea, loss of appetite in HIV and cancer patients, spasticity in multiple sclerosis and spinal cord injuries, neuropathic pain, non-neuropathic pain, Tourette syndrome, and glaucoma (Abrams et al., 2011, Ben Amar, 2006, Grotenhermen and Muller-Vahl, 2012, Kumar et al., 2001, Raby et al., 2009, Robson, 2001).

Due to potential side effects (including overdose) associated with opioid use (Centers for Disease Control and Prevention, 2011) and the decrease in analgesic efficacy over time (Lee et al., 2011), there is a need to explore alternative medications to opioids in the management of severe pain. While controversial, cannabis is being explored as a possible complement (Abrams et al., 2011) or alternative to opioids for reducing pain (Carter et al., 2015, Elikkottil et al., 2009, Lucas, 2012). Clinical and pre-clinical studies have documented the synergistic relationship between opioids and cannabis. In a review article, Elikkottil et al. (2009)) assessed the synergistic relationship between opioids and cannabis in both experimental studies with mice and rats and clinical studies with healthy subjects. They conclude that combining smaller doses of cannabis and opioids resulted in positive analgesic effects with fewer side effects than a larger dose of either drug alone. Abrams et al. (2011) also found that among chronic pain patients who were treated with opioids, vaporized cannabis augments the analgesic effects of opioids, which may allow for opioid treatment at lower doses with fewer side effects. Similar to clinical and experimental research, data from a community-based study of people who have been prescribed opioids for chronic non-cancer pain found that cannabis use for pain relief purposes was common and that study participants reported greater pain relief in combination with opioids than when opioids were used alone (Degenhardt et al., 2014).

Qualitative studies have recently found that people who use heroin report that they are able to temper or reduce their heroin use by using cannabis. In a sample of street-recruited PWID, study participants reported smoking cannabis to reduce anxiety and cravings experienced while transitioning away from daily heroin use (Wenger et al., 2014). In another qualitative study, Peters found that medical cannabis patients consistently reported using cannabis to substitute or wean off prescription opioids (Peters, 2013). All patients who were taking opioids reported reducing their overall drug use, specifically opioids, by using cannabis. Patients also reported that cannabis was preferred over opioids, eased withdrawal from opioids, and in some cases was more effective in relieving pain.

In this paper, we test whether there is a statistical association between cannabis use and the frequency of nonmedical opioid use in a large cross-sectional sample of street-recruited PWID.

Section snippets

Study procedures

We used targeted sampling methods to recruit PWID in Los Angeles and San Francisco, California, USA (Bluthenthal and Watters, 1995, Kral et al., 2010, Watters and Biernacki, 1989). Eligibility criteria included injection drug use in the past 30 days and being 18 years of age or older. Study staff verified that potential participants had injected drugs by inspecting them for signs of recent venipuncture (“tracks”; Cagle et al., 2002). Each participant went through an informed consent process

Results

The sample was nearly three-quarters men, one-third African American, one-third Latino, and one-third Caucasian, with the majority being over 50 years old (Table 1). Nearly one half reported having used cannabis in the past 30 days. Nearly all reported having used heroin in the past 30 days (95%), followed by nonmedical use of opioids (38%), methadone (26%), speedball use (20%), and goofball use (15%). The mean (and standard deviation) number of times participants used opioids nonmedically in

Discussion

We found that in this sample of street-recruited PWID who use opioids in Los Angeles and San Francisco, people who use cannabis used opioids less frequently. A number of possible explanations exist for this phenomenon. It is possible that PWIDs who use cannabis have a qualitatively different set of motivations than those who do not, or that PWIDs who use cannabis have a less severe form of opioid use disorder than those who do not. Alternatively, it may be that cannabis is deliberately or

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