Park rangers, scientists and now immigrants have all weathered attacks from America’s new president. Make no mistake: if they’re not after you now, they soon will be. It’s right and proper to be anxious and paranoid in times like these, but at least one culprit for an ill wind bringing you to unease can be ruled out.
As Broadly observed last week, there are a number of research studies that conclude marijuana users may develop anxiety disorder symptoms at a rate higher than the general, non-using public. But when Conal Twomey, a professor of psychology and researcher at the University of Southampton in the U.K., took a look at the studies, he found them wanting.
Most of the studies that concluded marijuana is a risk factor for anxiety were “cross-sectional,” as opposed to longitudinal.
For the 99 percent of us unfamiliar with research terminology, imagine the difference between a snapshot and a full-length documentary. Cross-sectional studies look at a discreet point in time; longitudinal studies observe subjects over an extended period—months, years, perhaps even decades, if the funding keeps coming. (The landmark study that concluded there’s no link between moderate marijuana smoking and lung ailments like cancer and COPD was a longitudinal study; so too was the study from Jamaica that found children whose mothers smoked marijuana while pregnant showed no difference in functionality and brain development than children of nonsmokers.)
Such short-term, limited “studies therefore cannot tell us about the directionality of the cannabis–anxiety association,” Twomey told Broadly’s Gabby Bess. “Is cannabis use causing anxiety, or are people with anxiety more likely to use cannabis due to the reported stress-relieving functions of the drug?”
Great question. And one without a solid answer, which Twomey did not set out to provide.
Twomey sought only to see if the research that claimed there was a link was any good. Most of it, he found, wasn’t. Most of it was cross-sectional.
When Twomey looked at only the long-term studies and controlled for other factors with known links to anxiety—including mental health problems—he found that even frequent marijuana users were only 1.15 times as likely to develop “elevated anxiety symptoms.”
That is, there are “very small odds” that a heavy stoner may be jumpier or more paranoid than casual cannabis users or non-users—and, Twomey concluded, there’s no demonstrated link between smoking marijuana and the sudden appearance of anxiety symptoms.
“[C]annabis use is no more than a minor risk factor for the development of elevated anxiety symptoms in the general population,” he wrote.
As it happens, results from a three-year longitudinal study in Sweden looking into marijuana use’s connection to depression and anxiety were released last year. Researchers found no long-term link between cannabis use and either malady. And a cross-sectional study conducted in Colorado, results of which were released in December, found no link between marijuana and anxiety, either.