Really? This is just Counter-Intuitional

I totally accept that Marijuana can have some very positive medical effects.  I don't understand HOW, but I get it helps with glaucoma.

And I totally understand the positive effects for pain and nausea.

But this one, well it runs counter to my understanding.

I mean I have talked to a lot of pot-heads who, when high, seem like they HAVE Alzheimer's.  So maybe it's true, but it sounds fishy to me.