Been a toker for the better part of 30 years. A year after I quit cigarettes, I had a lung xray. Doc said my lungs looked great, and he was glad I quit the cigs. As for so-called "cognitive" issues, I'd bet money these folks have used far more, harder drugs than MJ.
The truth is, pot is used by your mortgage brokers, bankers, lawyers, doctors, politicians and more. You only THINK you know what a typical toker looks like, based on outdated, ignorant stereotypes. If everyone you knew revealed themselves as the pot smokers they are, you'd feel really stupid for spouting off about things you know absolutely nothing about.
The funniest thing about pot smokers... is that they think that only the people that they confide in are aware of their habit. News flash! News flash! Everyone knows you are a pot head. Test it out today... ask someone you don't think knows that you smoke pot. If they have even a smidgen of awareness and they are honest they will tell you that they know.
I have lived and worked with pot heads my entire life.