The psychotropic effects of THC end within a few hours with vaping or smoking and within about 12-16 hours with oral ingestion. Detectable MJ metabolites exist for longer, but aren't psychoactive.
Just as the man who killed his wife from eating pot cookies, just as the suicide kid who jumped to his death after eating pot laced cookies. .
The high doses in edibles are a real problem. They should be cut by at least 75% per item. This should be regulated just as is beer %alcohol, etc.
One good thing about MJ is that a user tends to "never do that again" after getting too high a dose. Very different from alcohol, where the dose over time tends to go higher even after a bad experience (except for me, I threw up once and quit forever)
THC does not leave the system never to return. THC, particularly repeated use, does destroy brain capacity and function.
It is the old but true line, “use pot and nothing will happen to you.” and you continue to be nothing.
It is real simple pot smokers should not be allowed to drive at all. period.