From the University of British Columbia, Vancouver (J.R.B., H.C., S.E., J.A.S.), Dalhousie University, Halifax, NS (M.A.), and the Centre for Addiction and Mental Health (R.E.M.) and the University of Toronto (R.E.M.), Toronto - all in Canada.
N Engl J Med. 2022 Jan 13;386(2):148-156. doi: 10.1056/NEJMsa2109371.
The effect of cannabis legalization in Canada (in October 2018) on the prevalence of injured drivers testing positive for tetrahydrocannabinol (THC) is unclear.
We studied drivers treated after a motor vehicle collision in four British Columbia trauma centers, with data from January 2013 through March 2020. We included moderately injured drivers (those whose condition warranted blood tests as part of clinical assessment) for whom excess blood remained after clinical testing was complete. Blood was analyzed at the provincial toxicology center. The primary outcomes were a THC level greater than 0, a THC level of at least 2 ng per milliliter (Canadian legal limit), and a THC level of at least 5 ng per milliliter. The secondary outcomes were a THC level of at least 2.5 ng per milliliter plus a blood alcohol level of at least 0.05%; a blood alcohol level greater than 0; and a blood alcohol level of at least 0.08%. We calculated the prevalence of all outcomes before and after legalization. We obtained adjusted prevalence ratios using log-binomial regression to model the association between substance prevalence and legalization after adjustment for relevant covariates.
During the study period, 4339 drivers (3550 before legalization and 789 after legalization) met the inclusion criteria. Before legalization, a THC level greater than 0 was detected in 9.2% of drivers, a THC level of at least 2 ng per milliliter in 3.8%, and a THC level of at least 5 ng per milliliter in 1.1%. After legalization, the values were 17.9%, 8.6%, and 3.5%, respectively. After legalization, there was an increased prevalence of drivers with a THC level greater than 0 (adjusted prevalence ratio, 1.33; 95% confidence interval [CI], 1.05 to 1.68), a THC level of at least 2 ng per milliliter (adjusted prevalence ratio, 2.29; 95% CI, 1.52 to 3.45), and a THC level of at least 5 ng per milliliter (adjusted prevalence ratio, 2.05; 95% CI, 1.00 to 4.18). The largest increases in a THC level of at least 2 ng per milliliter were among drivers 50 years of age or older (adjusted prevalence ratio, 5.18; 95% CI, 2.49 to 10.78) and among male drivers (adjusted prevalence ratio, 2.44; 95% CI, 1.60 to 3.74). There were no significant changes in the prevalence of drivers testing positive for alcohol.
After cannabis legalization, the prevalence of moderately injured drivers with a THC level of at least 2 ng per milliliter in participating British Columbia trauma centers more than doubled. The increase was largest among older drivers and male drivers. (Funded by the Canadian Institutes of Health Research.).
加拿大（2018 年 10 月）大麻合法化对四氢大麻酚（THC）检测呈阳性的受伤司机的流行率的影响尚不清楚。
我们研究了不列颠哥伦比亚省四个创伤中心接受机动车碰撞治疗的中度受伤司机，数据来自 2013 年 1 月至 2020 年 3 月。我们纳入了在临床评估中需要进行血液检测的中度受伤司机（其病情需要进行血液检测），这些司机在完成临床检测后仍有多余的血液。血液在省级毒理学中心进行分析。主要结局是 THC 水平大于 0，THC 水平至少为 2 纳克/毫升（加拿大法定限值）和 THC 水平至少为 5 纳克/毫升。次要结局是 THC 水平至少为 2.5 纳克/毫升，血液酒精水平至少为 0.05%；血液酒精水平大于 0；血液酒精水平至少为 0.08%。我们在合法化前后计算了所有结局的流行率。我们使用对数二项式回归计算调整后流行率比，以在调整相关协变量后，对物质流行率与合法化之间的关联进行建模。
在研究期间，4339 名司机（合法化前 3550 名，合法化后 789 名）符合纳入标准。在合法化之前，9.2%的司机 THC 水平大于 0，3.8%的司机 THC 水平至少为 2 纳克/毫升，1.1%的司机 THC 水平至少为 5 纳克/毫升。合法化后，这些数值分别为 17.9%、8.6%和 3.5%。合法化后，THC 水平大于 0 的司机（调整后流行率比，1.33；95%置信区间[CI]，1.05 至 1.68）、THC 水平至少为 2 纳克/毫升（调整后流行率比，2.29；95%CI，1.52 至 3.45）和 THC 水平至少为 5 纳克/毫升（调整后流行率比，2.05；95%CI，1.00 至 4.18）的流行率增加。THC 水平至少为 2 纳克/毫升的司机中，年龄在 50 岁及以上的司机（调整后流行率比，5.18；95%CI，2.49 至 10.78）和男性司机（调整后流行率比，2.44；95%CI，1.60 至 3.74）的增加幅度最大。酒精检测呈阳性的司机的流行率没有显著变化。
在大麻合法化后，不列颠哥伦比亚省参与创伤中心的中度受伤司机中 THC 水平至少为 2 纳克/毫升的司机的流行率增加了一倍以上。这种增长在老年司机和男性司机中最大。（由加拿大卫生研究院资助）。
