When the participants drove a simulator two and five hours after taking the 10‑mg or 20‑mg gummies, they showed poorer lane control, slower reaction times and larger speed fluctuations, even though their blood THC concentrations stayed below the common 5 ng/mL legal cutoff.

Edibles are digested slowly, so THC reaches the brain gradually; this delayed absorption can produce noticeable impairment while the amount of THC measured in the blood remains relatively low.

In an earlier study by the same team that used smoked cannabis, drivers displayed similar levels of impairment only after their blood THC averaged 30.3 ng/mL – almost ten times higher than the levels seen after the edible doses.

Because standard roadside blood tests focus on the amount of THC in the bloodstream, they may miss drivers who are still impaired after eating edibles, creating a detection problem for police. Dr. José Ignacio Nazif‑Munoz of the Université de Sherbrooke explained that these biological differences pose a challenge for law‑enforcement and that the delayed absorption and prolonged effects of edible cannabis complicate the interpretation of biological measures.