Combining alcohol with marijuana increases your blood’s concentration of tetrahydrocannabinol or THC, the main psychoactive constituent of cannabis, according to a new study published in Clinical Chemistry this week.
The most frequently detected combination of substances linked to car accidents is cannabis with alcohol. Previous analyses have found that the increased accident risk of pot and booze use combined were higher than for either alone. Yet surprisingly, how the two compounds interact remain poorly understood.
To investigate, a team led by Marilyn Huestis from the National Institute on Drug Abuse recruited 32 adult cannabis users who smoked at least once in three months but not as much as four times a week. The participants were asked to drink a placebo or a low-dose alcohol 10 minutes before inhaling one of three things: a placebo, low-dose THC, or high-dose THC vaporized cannabis. Blood samples were taken before and up to eight hours after ingestion; 19 of the participants completed all the sessions.
With alcohol, the blood concentrations for both low and high THC doses were significantly higher than just smoking marijuana. The higher blood concentrations of THC likely explains the impaired performance that’s observed from the combined use of alcohol and cannabis. The team hopes that their results could help inform THC cutoffs for driving legislation.