There is no mention that these drivers were ONLY impaired by weed. But I can’t believe a paper would not look at the confounders. I know quite a few who are not

There is no mention that these drivers were ONLY impaired by weed. But I can’t believe a paper would not look at the confounders. I know quite a few who are not regular smokers but will imbibe after a few beers if it’s being passed around. Also weed is popular with consumers of stimulants. Without knowing the possible confounders, this statistic tells you very little.