Adults with a history of cannabis use have subtle, but long-lasting, changes to speech

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Stereotypical “stoner” speech and cadence have long been the butt of well-intentioned joking, but an Australia-led team of researchers wondered if weed consumers actually speak differently than non-consumers.They decided to collect speech samples from 31 adults with a history of cannabis use, low to moderate and with no illicit stimulant drug use, and 40 non-drug-using controls.

Specifically, participants provided a monologue, a sustained vowel, said the days of the week and read a phonetically balanced passage, notes the study, published online in Drug and Alcohol Dependence. Investigators then carried out an acoustic analysis of the samples for timing, vocal control and quality.

Researchers found some differences between those who had used cannabis and those who had not, but perhaps not as much as some may have expected.

“Subtle differences in speech timing, vocal effort and voice quality may exist between cannabis and control groups,” study authors write, but “data remain equivocal.”

After investigators controlled for lifetime alcohol and tobacco use and applied a false discovery rate, they report that the only difference between the two groups was spectral tilt, namely vocal effort and intensity.

This “appeared to change in line with duration of abstinence from cannabis use,” they write, perhaps meaning, “differences between groups may reflect longer-term changes to the underlying neural control of speech.”

Although researchers found that “cannabis users produced speech with greater variability in pause length and were less likely to maintain a constant intensity of vocalizations compared to non-users,” according to PsyPost, these were no longer significant once the false discovery rate was applied.

Verbling, an online language learning platform, reports that it takes about 100 muscles — including in the lips, tongue, throat, cheeks and jaw — to speak. “Every word or short phrase that is physically spoken is followed by its own unique arrangement of muscle movements,” adds Reference.

“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,” PsyPost quotes study co-author Adam Vogel as saying. Subtle alterations to speech from prolonged cannabis use “are likely not detectable to the human ear, but require specialized methods for identification of the small, but potentially genuine changes in performance,” Vogel told the publication.

A 2008 study looked at chronic cannabis users and the effect on motor function after 28 days of abstinence. “Residual diminished brain activation is still observed after discontinuing cannabis use in motor cortical circuits,” researchers found.

All in all, the authors of the most recent study note: “Our digital analysis of speech shows there may be a signal differentiating individuals with a history of recreational cannabis use from healthy controls, in line with similar findings from gait and hand function studies.”

A study published in 2017 concluded that “history of cannabis use is associated with long-lasting changes in open-chain elements of walking gait, but the magnitude of change is not clinically detectable.”

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