"We found no observational studies that met inclusion criteria, but a growing body of cross-sectional literature suggests negative opioid-related correlates among individuals who use cannabis and opioids concurrently. These include opioid misuse;9 [5],10 [5],99 [5],133 [5] a greater number of opioid refills;99 [5] a longer duration of opioid use; a higher dose of opioid medication prescribed;9 [5] and endorsement of using opioids and other pain medications without a prescription.134 [5]"
Links
[1] https://www.hsrd.research.va.gov/publications/esp/cannabis.pdf
[2] http://www.rethinkpot.org/tags/veterans
[3] http://www.rethinkpot.org/tags/opioid
[4] http://www.rethinkpot.org/tags/study-0
[5] https://www.ncbi.nlm.nih.gov/books/NBK476445/