Acute Effects of Marijuana on Speech

Exploratory research recently published in the journal Drug and Alcohol Dependence found that cannabis consumption may be linked to subtle but long-lasting changes in speech. This associated impact on speech is said to be linked to effects on cannabis consumers’ motor functions, explained by Psychology Dictionary as activity or movement like walking and speaking that requires our brains and muscles to work together.

The team of researchers explains that slow, labored speech output as a result of cannabis use has long been suggested, but there is extremely limited evidence to support it. Fortunately, this 2021 study shed some light on the situation.

Speech Study Reveals Vague Findings

The aim of the study was to assess the speech within individuals who have a history of recreational cannabis consumption in comparison to the speech of non-consumers. The study collected samples from around 31 adults with a history of cannabis consumption and around 40 non-consuming adults. The participants were required to complete simple and complex speech-related tasks, which included a monologue, saying days of the week, and reading a phonetically balanced passage (known as “The Godfather Passage”).

The research team recorded participants’ tasks and then analyzed the audio using acoustic analysis. This allowed the team to get insight into measures of timing, vocal control, and quality. The team explained that there were subtle differences between the two groups of participants, particularly in timing, vocal effort, and voice quality, but that the data “remained equivocal,” meaning the differences were too small to deduce any sound conclusions.

Co-author of the study, Adam Vogel, posted on Twitter, “Speech is sensitive to brain health. Changes that occur from drug use can lead to changes in behaviors and cognitive/motor acts, even in otherwise healthy adults.” By comparing those with a history of cannabis consumption to those who don’t, the team of researchers was able to identify if cannabis actually has effects on speech. However, participants who had a history of other drug use like opioids were not included, as that could also impact the results.

Vogel explained that they “controlled for alcohol and cigarette smoking in cohorts,” so the differences they reported were “not the result of those two aspects of the speaker.” One of the most noticeable differences was when the participants read from “The Godfather Passage,” during which those with a history of cannabis consumption exhibited increased vocal effort and reduced vocal quality and intensity.

“There may be changes in neurological function resulting from prolonged use of cannabis and these may manifest in subtle alterations to speech,” Vogel said to PsyPost. “These changes are likely not detectable to the human ear, but require specialized methods for identification of the small but potentially genuine changes in performance.”

The researchers also found that the cannabis group was found to produce speech that had greater variability in pause length and were less likely to maintain consistent vocal intensity when compared to the control group (those with no cannabis consumption history). However, the differences they found were not statistically significant, meaning that it’s still not 100% certain that cannabis impacts these speech features.

Vogel also explained to PsyPost that the data from the study was limited to a single time point, as subjects were not followed over time. “We are making assumptions that the differences we observed between groups (cannabis vs. non-drug users) were the result of cannabis use and not something else we haven’t accounted for.”

So, What Does This Mean for Cannabis Consumers?

On its face, the study appears to support the potential for negative effects from regular cannabis use, but it ultimately needs more information to back any claims—a common trope when it comes to in-depth cannabis research. This means that cannabis consumers should be aware of a potential long-term impact on speech, but there is no guarantee this risk will be realized.

It’s also crucial to acknowledge that the potency of the cannabis consumed plays a role. For example, many have claimed (without concrete evidence) that slurred speech is a side effect of cannabis consumption. While the claim has not been comprehensively studied, slurred speech may actually be a result of consuming high-potency cannabis or high quantities that lead to intense highs. In fact, adverse side effects of cannabis are increasingly being linked to high potency.

A much older study, published in 1986, assessed the acute effects of cannabis on social conversation and also found that the speech quality of cannabis consumers significantly decreased. This study concluded by stating, “Marijuana appears to be an exception to the general rule that drugs of abuse increase verbal interaction.” However, this study has significant limitations since it was largely observational and conducted during a time when research on cannabis was tightly restricted.

Part of responsible cannabis consumption is proactively exploring the effects of the plant, both good and bad. Though research suggests there may be minor risks to be aware of as a regular cannabis consumer, the findings are not yet conclusive enough to cause alarm. One should also keep in mind the many proven medical benefits of cannabis that arguably outweigh the potential negatives.

Have you noticed any changes in your own speech since engaging in frequent cannabis consumption? Let us know in the comments below.