By Pat Anson, PNN Editor

It’s a common belief that cannabis may reduce the use of opioids and may even help solve the opioid crisis. But a new study by researchers at Columbia University Mailman School of Public Health found that people with substance abuse problems are just as likely to use heroin or to misuse prescription opioids on days when they consume cannabis.

The study, published in the journal Addiction, is believed to be one the first to test whether adults with substance abuse problems are substituting opioids with cannabis. Researchers followed 211 adults in the New York City area for 90 days, asking if they had used cannabis, heroin, or misused prescription opioids.

Participants were mostly male, unemployed, unmarried, and had a high prevalence of substance misuse and pain. “Misuse” of prescription opioids was defined as taking more pain medication than prescribed or without a prescription.

On average, participants reported they used cannabis on 15% of days without opioids, opioids were used on 15% of days without cannabis, and both cannabis and opioids were used on 7% of days. On days that participants used cannabis, the odds of using opioids nearly doubled. The findings were consistent whether participants were experiencing pain or not.

"Our results suggest that cannabis seldom serves as a substitute for non-medical opioids among opioid-using adults, even among those who report experiencing moderate or more severe pain," said Deborah Hasin, PhD, professor of epidemiology at Columbia Mailman School. "In other words, our study suggests that cannabis is not an effective way to limit non-medical opioid use."

Cannabis Users Need More Anesthesia

Another recent study found that cannabis may actually raise pain levels for patients recovering from surgery. In an analysis of 118 patients who had surgery for a broken leg at a Colorado hospital, researchers found that cannabis users needed more anesthesia during surgery than non-users. They were also more likely to have post-operative pain and use higher doses of opioid pain medication while hospitalized.

The findings, presented at the annual meeting of the American Society of Anesthesiologists, adds to the growing body of research suggesting that patients who use cannabis have higher anesthesia needs and more surgery-related pain.

"There is some evidence that cannabis may be beneficial for chronic and nerve pain. However, early research suggests that this is not the case for acute pain such as for surgery of a broken leg," said lead author Ian Holmen, MD, an anesthesiology resident at the University of Colorado Hospital in Aurora, where the study was conducted.

"We now understand patients who chronically use opioids prior to surgery often have exaggerated pain responses and need increased pain medication after surgery because they have an increased tolerance. We speculate that cannabis use may cause a similar effect, but we need more research to determine if this is the case."

Holmen and his colleagues found that cannabis users had higher pain scores while recovering from surgery and received 58% more opioids per day while hospitalized. They also needed about a third more anesthesia. The amount of anesthesia during surgery is typically based on observations of a patient’s involuntary body movements, increased heart rate, high blood pressure or increased rate of breathing, which are signs the patient may be experiencing more pain.

Researchers did not include in the study patients who suffered from chronic pain or those who had previously been prescribed opioids.

"This study shows that it is important for patients to tell their physician anesthesiologist if they have used cannabis products prior to surgery to ensure they receive the best anesthesia and pain control possible, including the use of non-opioid alternatives," said Holmen. "It also confirms that more research is needed to understand how cannabis impacts pain."

A 2019 study of patients who had colonoscopies found that regular marijuana users required three times the amount of a common sedative, propofol, as did nonusers.