Adults with substance use problems may be more likely to misuse opioids on days when they use cannabis, a study in New York suggests. Researchers examined data from 13,271 days of observation for 211 adults who had problem substance use and who used non-medical opioids. At baseline, participants were asked if they used cannabis, whether they used opioids with or without a prescription, and whether they experienced moderate or severe pain. Then they answered questions about cannabis and opioid use daily for the next 90 days. Participants were almost twice as likely to use non-medical opioids on days when they reported cannabis use (adjusted odds ratio 1.86). The relationship between cannabis use and opioid use didn't appear to change based on whether participants reported moderate-to-severe pain or lower levels of pain at baseline, suggesting that cannabis isn't being used as a substitute for non-medical opioids, researchers report in Addiction. "Possible explanations are that they found that using the two types of substances together produced an effect they liked better than using just one of the substances," said senior author Deborah Hasin of Columbia University Irving Medical Center in New York City. "Another possible explanation is that while they used both in the same day, they used cannabis and non-medical opioids at different times within the 24 hours, depending on what they were doing," Hasin said by email. "Future studies need to look into this more." Participants' mean age was 43 years old, 64% were male, 78% were unmarried, and 80% were unemployed. At baseline, roughly half of them reported experiencing moderate to severe pain over the previous 30 days. On average, participants reported using opioids without cannabis on 14.6% of days, cannabis without opioids on 15% of days, and both cannabis and opioids on 7.1% of days. They reported using neither cannabis nor opioids on 63.2% of days. One limitation of the study is that substance use was self-reported, the study team notes. Another drawback is that pain was only assessed once, at baseline, making it impossible for researchers to measure whether heavier cannabis use might be a substitute for opioid use or if it might lead to a using a lower amount of opioids. "This study suggests that rather than a substitute, it's possible that cannabis is a complement to opioid use among people with substance use disorders," said Chelsea Shover, a researcher at Stanford University School of Medicine who wasn't involved in the study. "The evidence does not support recommending cannabis to replace opioids for people with substance use disorders," Shover said by email. "This is a really important finding because it stands in contrast to the cannabis industry advertising their products to address the opioid overdose crisis and a few states that actually have opioid use disorder as a qualifying condition for medical cannabis." —Lisa Rapaport Source
