Study: THC Metabolite Present for Extended Periods of Time in Young Adults Following Abstinence

Boston, MA: The inert THC metabolite, carboxy-THC may be present for periods of time exceeding 25 days in young adults who have ceased their use of the substance, according to clinical data published in the Journal of Psychopharmacology.

A team of investigators from Harvard Medical School, John Hopkins University, and Massachusetts General Hospital assessed carboxy-THC detection times in a group of 70 adolescents and young adults (ages 15 to 25) during one-month of monitored abstinence.

Forty percent of subjects tested positive for the presence of carboxy-THC in urine for time periods exceeding 25 days. Investigators estimated that at least some subjects would continue to test positive for up to 80 days. Subjects’ sex and body mass index influenced carboxy-THC elimination patterns.

Authors concluded, "[These] findings underscore that, as with adults, detectable cannabinoid metabolites do not necessarily indicate recent use in adolescents and young adults. … Findings desperately call novel assays that can be administered at single time-points that can detect recent cannabis exposure and intoxication in both adults and adolescents."

Prior studies, such as those here and here, have identified the presence of carboxy-THC for periods of time exceeding 80 to 100 days post-abstinence in former adult users. As a result, the United States National Highway Traffic Safety Administration acknowledges: "Detection of total THC metabolites in urine, primarily THC-COOH-glucuronide, only indicates prior THC exposure. Detection time is well past the window of intoxication and impairment. … It is … currently impossible to predict specific effects based on THC-COOH concentrations."

For more information, contact Paul Armentano, NORML Deputy Director. Full text of the study, "Urinary 11-nor-9-carboxy-tetrahydrocannabinol elimination in adolescent and young adult cannabis users during one month of sustained and biochemically-verified abstinence," appears in the Journal of Psychopharmacology.