New data on opioid-related A&E visits debunks cannabis “gateway drug” theory

Cannabis legalisation leads to a temporary decline in opioid-related emergency visits, indicating it is not serving as a “gateway” drug, says a new study.

A new study has found that states which legalise recreational cannabis experience a short-term decline in opioid-related emergency department visits.

This was particularly prevalent among 25 to 44-year-olds and men, according to an analysis led by the University of Pittsburgh Graduate School of Public Health.

Published in the journal Health Economics, the study shows that even after the temporary decline wears off, recreational cannabis laws are not associated with increases in opioid-related emergency department visits.

The opioid epidemic in the U.S. has accelerated in recent years, with more than 81,000 drug overdose deaths between June 2019 and May 2020, the highest ever recorded in a one-year period, according to the US Centre for Disease Control and Prevention.

Researchers analysed data on emergency department visits involving opioids from 29 states between 2011 and 2017. 

The study included four states that legalised recreational marijuana during that time frame: California, Maine, Massachusetts and Nevada. 

These four states experienced a 7.6 percent reduction in opioid-related emergency department visits for six months after the law went into effect, compared to the states that didn’t implement such laws. 

On closer inspection, the team found that men and adults aged 25 through 44 primarily drove the reduction. 

Although the downturn in emergency department visits for opioids does not continue over six months, the study’s authors said it is encouraging that visits also don’t increase above baseline after recreational cannabis laws are adopted. 

This indicates that recreational marijuana is not serving as a “gateway” to opioids.

“A decline in opioid-related emergency department visits, even if only for six months, is a welcome public health development,” said lead author Coleman Drake, Ph.D., assistant professor in Pitt Public Health’s Department of Health Policy and Management. 

“We can’t definitively conclude from the data why these laws are associated with a temporary downturn in opioid-related emergency department visits but, based on our findings and previous literature, we suspect that people who use opioids for pain relief are substituting with cannabis, at least temporarily.”

Drake added: “Cannabis can provide pain relief for persons using opioids, but cannabis ultimately is not a treatment for opioid use disorder. 

“States can fight the opioid epidemic by expanding access to opioid use disorder treatment and by decreasing opioid use with recreational cannabis laws. These policies aren’t mutually exclusive; rather, they’re both a step in the right direction.”

The study follows findings published earlier this year which stated that claims of cannabis being linked to the later use of other controlled substances are not supported by the data.

A pair of researchers affiliated with Boise State University in Idaho analysed the relationship between self-reported cannabis use in late-adolescence and the use of other illicit substances later in life in a nationally representative sample. 

They stated: “Any public policy that prohibits the use of marijuana in an attempt to curb hard drug use is unlikely to succeed.”