WASHINGTON – New research appearing online today in Clinical Chemistry, the journal of AACC, shows that cannabis can be detected in the blood of daily smokers for a month after last intake. The scientific data in this paper by Bergamaschi et al. can provide real help in the public safety need for a drugged driving policy that reduces the number of drugged driving accidents on the road.

Cannabis is second only to alcohol for causing impaired driving and motor vehicle accidents. In 2009, 12.8% of young adults reported driving under the influence of illicit drugs and in the 2007 National Roadside Survey, more drivers tested positive for drugs than for alcohol. These cannabis smokers had a 10-fold increase in car crash injury compared with infrequent or nonusers after adjustment for blood alcohol concentration.

In this paper, 30 male chronic daily cannabis smokers resided on a secure research unit for up to 33 days, with daily blood collection. Twenty-seven of 30 participants were THC-positive on admission, with a median (range) concentration of 1.4 µg/L (0.3–6.3). THC decreased gradually with only 1 of 11 participants negative at 26 days; 2 of 5 remained THC-positive (0.3 µg/L) for 30 days.

These results demonstrate, for the first time, that cannabinoids can be detected in blood of chronic daily cannabis smokers during a month of sustained abstinence. This is consistent with the time course of persisting neurocognitive impairment reported in recent studies and suggests that establishment of ‘per se’ THC legislation might achieve a reduction in motor vehicle injuries and deaths. This same type of ‘per se’ alcohol legislation improved prosecution of drunk drivers and dramatically reduced alcohol-related deaths.

“These data have never been obtained previously due to the cost and difficulty of studying chronic daily cannabis smoking over an extended period,” said Dr. Marilyn A. Huestis of the National Institutes of Health and author on the paper. “These data add critical information to the debate about the toxicity of chronic daily cannabis smoking.”

Reporters who wish to receive a copy of the study or arrange an interview with the authors may contact Molly Polen at 202-420-7612 or mpolen@aacc.org


About AACC

Dedicated to achieving better health through laboratory medicine, the American Association for Clinical Chemistry (AACC) brings together more than 50,000 clinical laboratory professionals, physicians, research scientists, and business leaders from around the world focused on clinical chemistry, molecular diagnostics, mass spectrometry, translational medicine, lab management, and other areas of breaking laboratory science. Since 1948, AACC has worked to advance the common interests of the field, providing programs that advance scientific collaboration, knowledge, expertise, and innovation. For more information, visit www.aacc.org.