Here's a Washington Post article. It says the opposite though it looks at it in a different fashion. You can find a link to anything. People pay for studies to reflect what they want. That one obviously was paid for by the old clueless people who believe Reefer Madness was a documentary. Maybe the Washington Post are a bunch of hippies... right?
And 9 to 17 (whatever) is not a large enough sample size for any test. So, it's basically poppycock.. and also a bit misleading. Though they attempt to explain, they do a very poor job of it and gloss over the most important part.
They cannot through current drug testing determine when a person used! So, they cannot in any definitive way know if they were impaired or not. They gloss over that fact with one short sentence, which in turn misrepresents the whole article. Let alone not having near enough sample size to determine anything.
They can only
guess based on thc level in the blood. Sure in most instances they could be correct as more thc means more probability that it was used. But, that still means nothing ..
Science: THC (which is type of cannabinoid) by itself does not get anyone high, it's a combination of chemicals and ratio of the chemicals known as cannabinoids (CBD, CBN) that help THC. If those cannabinoids are in too large amount, or too small, nothing happens, regardless of the THC level. And yet the thc level will still read positive and high though the person may never had been impaired at all.
Science: the reason why they have such a hard time coming up with a valid test is because every living multi cell creature on the planet has
cannabinoid receptors throughout their brains, organs and nervous system. The body does not recognize it as a poison, like most man made drugs, so, it's much harder to test for. Plus, it's a very complicated plant and they've only identified a small portion of the chemicals in it.
Fact: these receptors ONLY except cannabinoids.
Nothing else.
Fact:
The human brain has more cannabinoid receptors than any other G protein-coupled receptor (GPCR) type.
Why? Why are they there?
Note: in the wiki article (wiki is a poor choice for information, sorry) it states mammalian brain, that is false, as fish, reptiles, birds and even smaller cellular creatures have endocannabinoid systems.
Educate yourself ... ignorance helps no one.