Cannabis & Hospitalization

Cannabis and hospitalization go hand-in-hand, according to a new study. Cannabis users are 22 percent more likely to visit emergency departments and require hospitalization. Led by researchers from Unity Health Toronto, they surveyed 4,800 cannabis users over a 12-month period. They compared the data to 10,000 people who had never used cannabis.

Despite the observational nature of the study, the study’s lead author, Dr. Nicholas Vozoris, to CTV:

“Our analyzes are adjusted and controlled for all of these other factors, making it less likely that the other factors explain the positive ER visit and hospitalization.”

Observation vs. experimental research

Among the reasons for hospitalization or visits to the emergency room, cannabis users cited acute trauma (15%) as the most common cause. Followed by breathing problems (14%) and gastrointestinal problems (13%).

But the study was observational and therefore could not say that cannabis use leads to higher hospitalization rates. This was a correlation study. Despite the lead investigator’s claim, this study did not test a specific intervention against a control group. They just looked at data from certain groups and drew a conclusion.

Observational research can educate us about the types of associations between lifestyle and risk of a particular disease. But all they can do is show correlations. Even the researchers admitted this given their small sample size. They said more research is needed to confirm the “possible link between all-cause mortality and respiratory disease.”

Bias of the cannabis and hospitalization study

Because this was an observational study with no control group, the claim that the study controlled for other factors of hospitalization, such as alcohol use, opioid use, prescription drug use, underlying mental health or medical conditions, is obviously false.

The study did not compare rates of emergency department visits and hospitalizations among cannabis users to rates among users of alcohol, opioids, prescription drugs, or other substances. The lead researcher, Dr. Vozoris said he is not aware of any existing research comparing these rates.

Vozoris hopes this study will educate the public that cannabis is not risk-free. But what exactly, if anything, did this study prove?

The Problem with the Cannabis and Hospitalization Study

dr John Ioannidis, a professor at Stanford University, is critical of observational study research. In his article “Why Most Published Research Findings are False,” he explains that “research findings are often simply accurate measures of the prevailing bias.”

And that seems to be the case here.

Nothing in this study suggests why cannabis users would have more frequent hospitalizations and emergency room visits.

Suppose there are factors that the researchers didn’t take into account. The only way to really determine a cause between two variables is to conduct an experimental study such as a randomized controlled trial. Many observational studies can confirm that cannabis users have higher hospitalization rates. But without randomized controlled trials, this correlation tells us nothing.

It’s like the correlation between Nicolas Cage movies and drowning in swimming pools. No serious researcher would publish a paper highlighting this connection, concluding that more observational research is needed, and then reminding people that “Nicolas Cage films are not risk-free.”

That’s essentially what happened here.

That’s why studies like this always require “further research.” All they have to do is claim a possible link between cannabis and hospitalization. But with observational research, it’s impossible to say that x causes y. If anything, “further research” will increase the number of studies claiming a link between cannabis and hospitalizations, mudding the waters for researchers doing real science.