A new study focusing on how cannabis affects driving ability reveals that cannabis remains detectable in the body for a month after intake.
While cannabis is the second-most-common cause of impaired driving accidents, its effects on driving ability are not fully known.
But new research published Friday in the American Association for Clinical Chemistry's Clinical Chemistry journal finds that cannabis can be found in the blood of daily users for up to a month after last intake. This is important for laws pertaining to marijuana use and how it relates to operating motor vehicles, since enforcement of any marijuana laws requires testing for intoxication, as well as a cutoff for that intoxication.
The study used 30 males who smoked cannabis on a daily basis living at a secure research facility, where they stayed for up to 33 days. Blood was collected daily. Of the 30, 27 tested positive for THC when admitted and had a median concentration of 1.4 micrograms THC per liter of blood. After 26 days, only one of 11 participants tested negative for THC. Two of five were still THC-positive at 30 days.
"These data have never been obtained previously due to the cost and difficulty of studying chronic daily cannabis smoking over an extended period," Dr. Karylin Huestis, of the National Institutes of Health and an author of the study, told Science Daily. "These data add critical information to the debate about the toxicity of chronic daily cannabis smoking."
This research should prove useful in developing laws regarding marijuana use and motor vehicle operation, and should lead to new tests for determining whether a person is impaired after using cannabis, and to determine how long after use that person is impaired.
(Edited by Lois Heyman)
