“alcohol’s effects will usually be gone in no more than eight hours. “
Not even close. It depends on the amount consumed and many doctors consider the effects of alcohol to be 24 hours. For flying, it is a minimum 8 hours bottle to throttle, however, there is also the 0.04 BAC standard that now applies because we know 8 hours isn’t nearly enough depending on the consumption level.
Has there been similar research done on the lingering effects of marijuana use by pilots?