Does weed make you dumb?

Sarah smoked pot, now she’s a catatonic puddle; Andy took a hit, now he’s the dimmest bulb in the dojo.

Much like alcohol, cannabis’ immediate effects aren’t known for fostering intellect or improving motor functions. Writing your dissertation or operating heavy machinery while high would, clearly, be ill-advised.

But detractors claim the loosened, goofball state that characterizes most recreational use won’t simply go away in a few hours. Rather, long-term use could lead to a loss in cognitive functions and decision-making. You know… “dumb”.

Does cannabis change the brain?

“Findings are quite inconsistent as to whether there are microstructural changes to the brain,” says neuroscientist and endocannabinoid researcher Greg Gerdeman, PhD. “There are as many brain imaging studies that fail to find structural changes as those that do,” reports Gerdeman, a member of the International Cannabinoid Research Society.

One such study noted that though cannabis consumers showed a 2.3 percent smaller left amygdala—a primary centre for emotional regulation—the figures weren’t outside of what researchers called “normal variation”, and attributed the differences to genetic and environmental factors.

Gerdeman says studies that have detected structural changes have also reported greater connectivity between regions, both in terms of structure and functionality. He explains that while certain reports have shown the orbitofrontal cortex (OFC)—one of the brain’s primary decision-making and emotion-processing centres—of long-term cannabis consumers contain less grey matter than non-consumers, the brain may compensate in areas where it identifies deficiencies.

Much like alcohol, cannabis’ immediate effects aren’t known for fostering intellect or improving motor functions. Writing your dissertation or operating heavy machinery while high would, clearly, be ill-advised.

Another study found that while, compared with controls, pot users had notably less volume in the orbitofrontal region, they found higher functional connectivity in the OFC network, and higher structural connectivity in the areas that stimulate the OFC—their brain appeared better-equipped to “talk” to itself, so to speak. It’s unclear whether that increase in the brain’s ability to communicate with its many parts remains or degrades over time, however.

Though adolescent use of cannabis is shown to be detrimental to the development of many key functions in young brains, Gerdeman says almost all frequently cited studies reference adolescent use exclusively, or fail to control for adults who may have begun use in adolescence—potentially skewing results by reporting deficiencies that were caused by teenage use. Declines in function, such as a drop in IQ, are almost always sourced from subjects who initiated high levels of cannabis use at an early age.

“For example, kids under the age of 15 smoking high-THC cannabis—15 percent or more—on a daily, chronic basis, that’s not something that anyone should recommend,” he notes.

Does heavy cannabis use spur slower executive function?

The studies also focus on heavy consumers—frequently those who consume three or more times per day—which may limit their applicability to those whose enjoyment of the plant is less pervasive. Although cannabis’ effect on the brain’s wiring is up for debate, Gerdeman admits its association with “slowness” isn’t entirely unfounded.

“There is good evidence that long-term, frequent cannabis use leads to a measurable slowing of performance on standardized tasks of executive function,” says Gerdeman. Although not specified, those tasks perhaps include anything that would require those executive, decision-making functions.

That said, Gerdeman notes there’s equally strong evidence these performance effects dissipate rapidly when users take a break—say, anywhere from a few days to a week—from daily use.

Rethinking the “dumb” perception

For those hoping to avoid fulfilling the sluggish stoner stereotype, Gerdeman advises of CBD: “It is evident that having CBD present can influence both the acute psychoactivity and long-term negative consequences of chronic, frequent cannabis use.”

He also encourages others to reconsider what we think “dumb” is, and submits artists and known cannabis-consumers as a prime example. “If we were to do cognitive tests on the Snoop Doggs and Willie Nelsons of the world, they might perform slower… but to say they’re ‘dumb’ would be wrong,” Gerdeman maintains.