My understanding is that THC is absorbed in the body's fat cells and that it takes a couple of days to clear the system. But unless one's smoked outrageous amounts in one sitting, their brain will be functioning pretty normally once the high has passed.
This is just my understanding and if anyone's got links or facts to refute what I've just said, please post.
Don't feel like bringing links but will mention a few corrections. None change the thrust of your point so they are mere quibbles.
THC is, indeed absorbed into fat cells. It does not clear the system in a few days and can remain for an extended period. It does, however, clear the system insofar as detection is concerned quite quickly.
Most detection tests won't be able to detect anything beyond a month.
A follicle test can detect far past that depending on the individual's hair.
Smoking an outrageous amount will in one sitting
is not an established danger.
Most misgivings about pot are about long-term heavy use as the implications of this have not yet been studied very well.
But that too is simply a question mark and not an established danger.
Of course, the prolonged heavy use might make a big difference without it being pysiological, just a matter of the user being high for a significant portion of their life and this affecting their mentality.
For example, pot has an effect on short term memory, and if one is always high this can translate into an effect on long term memory merely on the basis of so many short term hinderances.