In observational and retrospective studies, people who use cannabis are more likely than people who do not use cannabis to also use other drugs. People who take medical cannabis are also more likely to report medical and non-medical use of opioid analgesics, stimulants, and tranquilizers. Given that people who take medical cannabis and those who do not are likely to have different underlying morbidity, it is possible that medical cannabis use reduces prescription drug use yet prescription drug use remains relatively high. Studies comparing people who take medical cannabis with people who do not take it cannot draw conclusions about the effect of medical cannabis on drug use. To fully understand the effect of medical cannabis on the use of other drugs, prospective longitudinal studies randomizing individuals to cannabis versus other treatments are urgently needed.
Division of General Internal Medicine, Department of Medicine, Montefiore Medical Center/Albert Einstein College of Medicine, Bronx, NY (MAB, JHA, COC); Community Health and Social Medicine, City University of New York, School of Medicine, New York, NY (NS).
Send correspondence to Nancy Sohler, PhD, MPH, 160 Convent Avenue, Harris Hall, New York, NY 10032. E-mail: firstname.lastname@example.org.
Received 20 February, 2018
Accepted 24 February, 2018
Funding: This work was funded in part by grants from the National Institute on Drug Abuse of the National Institutes of Health (R01DA032552, K24DA036955, and K08DA043050). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Disclosure: The authors declare no conflicts of interest.