Veterans with both opioid and cannabis use disorders had fewer opioid prescriptions but more psychiatric hospitalizations | Research

The takeaway

Among veterans with drug use disorders, those with co-occurring opioid and cannabis use disorders received fewer opioid prescriptions than those with opioid use disorder alone, but had higher rates of psychiatric admission and homelessness.

People following the opioid-cannabis substitution debate, harm reduction advocates, and those interested in substance use disorder research.

234,181 veterans: OUD+CUD group had 1.95x higher psychiatric admission risk

What the researchers found

Veterans with co-occurring OUD and CUD received fewer opioid prescriptions (mean 3.79 vs 4.8) compared to the OUD-only group, but had a higher likelihood of inpatient psychiatric admission (RR = 1.95) and homelessness (RR = 1.52).

Why it matters

The idea that cannabis might substitute for opioids has gained attention, but this study shows the relationship is complicated. While cannabis co-use was associated with fewer opioid prescriptions, it didn't translate to better overall outcomes.

The numbers in context

234,181 veterans studied (94% male). Co-occurring OUD+CUD group: 8.6% of sample. Mean opioid prescriptions: 3.79 (OUD+CUD) vs 4.8 (OUD only). Psychiatric admission risk ratio: 1.95. Homelessness risk ratio: 1.52. No significant difference in ED visits.

How the study worked

Retrospective analysis of 234,181 veterans with drug use disorder diagnoses from the National Veterans Health Administration, comparing outcomes across four groups: co-occurring OUD+CUD, OUD only, CUD only, and other drug use disorders using logistic and linear regression models.

What this study cannot tell us

Retrospective design cannot establish causation. The veteran population is predominantly male, limiting generalizability. Cannabis use disorder is clinically different from controlled medical cannabis use. Self-reported SC use relied on honesty.

How to read the evidence

Moderate: large national dataset with regression modeling, but retrospective and observational.

When this study was published

Published in 2019, using FY2012 data.

The bigger picture

The opioid-cannabis substitution hypothesis is appealing but oversimplified. These findings suggest that while cannabis co-use correlates with lower opioid prescribing, the people using both substances face compounding challenges that outweigh any prescribing reduction.

Questions still open

Would supervised medical cannabis programs for OUD patients show different outcomes than the uncontrolled co-use patterns seen here? Are the worse psychiatric outcomes driven by the combination of substances or by underlying severity?

Common questions

Does cannabis help people use fewer opioids?

In this study, veterans with both opioid and cannabis use disorders received fewer opioid prescriptions. However, they also had worse outcomes in other areas like psychiatric hospitalization, so the picture is more complex than simple substitution.

Why were psychiatric admissions higher in the dual-use group?

The study couldn't determine causation. It may reflect greater overall substance use severity, compounding effects of multiple substances, or other unmeasured factors common to people with multiple use disorders.

Read the original research

Adverse Consequences of Co-Occurring Opioid Use Disorder and Cannabis Use Disorder Compared to Opioid Use Disorder Only.

The American journal of drug and alcohol abuse, 45(5), 527-537

View on PubMed ↗Publisher’s paper ↗

Citation

De Aquino, Joao P; Sofuoglu, Mehmet; Stefanovics, Elina; Rosenheck, Robert. (2019). Adverse Consequences of Co-Occurring Opioid Use Disorder and Cannabis Use Disorder Compared to Opioid Use Disorder Only.. The American journal of drug and alcohol abuse, 45(5), 527-537. https://doi.org/10.1080/00952990.2019.1607363