Cannabis use can cause speech detriment, study finds

13th September 2021

Even low-to-moderate cannabis use could be associated with abnormalities in speech production as, apparently, the drug has a long-lasting impact on our motor functions.

According to PsyPost, a new study has identified a concerning link between cannabis use and the growing number of issues with speech production, including problems regarding timing, vocal control and quality.

The researchers who published their findings in the journal Drug and Alcohol Dependence report that, while it has long been known that depressants and hallucinogenic drugs could cause “acute changes” in the users’ speech, the latest findings suggest that they have long-lasting effects as well.

Study co-author Adam Vogel, a professor and director of the Centre for Neuroscience of Speech at the University of Melbourne, told PsyPost: “Speech is sensitive to brain health.

“Changes that occur from drug use can lead to changes in behaviours and cognitive/motor acts, even in otherwise healthy adults.

“ Professor Gabrielle Todd’s research group is focused on identifying changes in motor function that may occur from drug use.”

The study invited 31 people with documented, past cannabis use and 40 people who haven’t tried drugs before.

The participants were asked to complete five different tasks: a one-minute unprepared monologue, a sustained vowel, repeating “pa-ta-ka” as quickly and clearly as possible for 10 seconds, saying the days of the week, and reading a phonetically balanced text known as “The Grandfather Passage.”

Among other things, the researchers found that cannabis users needed to “increase vocal effort” to read “The Grandfather Passage” and also they produced speech with “greater variability” in pause length.

Mr Vogel added: “There may be changes in neurological function resulting from prolonged use of cannabis and these may manifest in subtle alterations to speech.

“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.

“Data for this study are derived from a single time point, that is, 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.”

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