Using marijuana and opioids together to treat chronic pain is a bad idea, according to a recent study published Tuesday in MedPage Today.

Researchers at the University of Houston found that chronic pain sufferers who combined marijuana and opioids had higher instances of anxiety, depression, and abuse of alcohol and other substances than those who treated their pain with opioids alone.

The study also showed no difference in both groups of patients' pain levels.

"The things psychologists would be most worried about were worse, but the thing patients were using the cannabis to hopefully help with, namely pain, was no different," Andrew Rogers, the study's lead author told MedPage Today.

"Co-use of substances generally leads to worse outcomes. As you pour on more substances to regulate anxiety and depression, symptoms can go up," he said.

Rogers and his team presented the study's findings at the annual American Pain Society Scientific Meeting in Milwaukee, Wisconsin, last week.

What do experts say?

Dr. Kevin Sabet, president of Smart Approaches to Marijuana, said the study confirmed previous research and debunks the argument that marijuana legalization could be the answer to stopping the opioid addiction crisis.

"Once again, another study completely shreds the arguments perpetuated by marijuana lobbyists that legalization can help solve the opioid epidemic," Sabet said in a news release. "Simply put, lawmakers must stop rushing ahead of the literature when it comes to expanding the use of this drug and possibly adding fuel to the addiction fire that is devastating our communities."

Another recent study by researchers at Stanford University in California found that medical marijuana users are more likely to use and abuse prescription pain medication, tranquilizers, and stimulants.

"These results are not surprising and indeed replicate other studies showing that cannabis use by pain patients is associated with higher doses of opioids and no pain relief benefits," Keith Humphreys, one of the researchers involved in the Stanford study, told MedPage Today. "This is one of many examples where claims about the benefits of medical cannabis are not supported by evidence," he added.

How was the study conducted?

The study surveyed 450 adults who at the time of the study used opioids for chronic pain that persisted for at least three months.

Seventy-five percent of the study's participants were women with an average age of 39.

Nearly 40 percent reported using recreational marijuana in the past three months, along with opioids.

Limitations of the cross-sectional study included its reliance on self-reported data. Additionally, the frequency or quantity of the participants' cannabis or opioid use wasn't assessed.