Table 1

Presence of tetrahydrocannabinol and other driving-impairing substances in the oral fluid of Spanish drivers according to confirmation analysis data (years 2011–2016)

CategoryTHC positivity
N=51 869 (n/%)
Median/Q1–Q3 of THC concentration (ng/mL)
THC alone25 516/49.2119.1/37.3–351.8*
THC in combination with26 353/50.8108.2/24.1–368.4*
 Cocaine22 679/43.7108.6/23.9–372.8**
 Amphetamines8048/15.5112.4/23.5–391.1**
 Opioids2936/5.763.6/11.7–257.8**
 Benzodiazepines1731/3.390.9/17.8–357.6**
 Z-drugs27/0.185.3/5.9–400.0**
∗Mann-Whitney U test (p) for THC alone versus THC in combination with
∗∗Kruskal-Wallis H test (p) across cocaine, amphetamines, opioids, benzodiazepines and Z-drugs
Cohen’s d effect size (judgement)
427.4 (0.0001)
453.1 (0.02)
0.746 (moderate)
  • Q, quartile; THC, delta-9-tetrahydrocannabinol; Z-drugs, zopiclone and zolpidem.