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**
∗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.