I'm a 63 yo male.  I've smoked marijuana since my early 20's.  Most of my life of smoking seldom involved smoking during the week, just the weekends.  I've never been a heavy user.  Suddenly one day about 6 years ago I stopped getting the familiar head buzz.  I've spoken to a couple of doctors who said they never heard of that happening to anyone.  I do have all the other conditions of smoking; cotton mouth, munchies and running off at the mouth, just no head buzz. 

I had been hospitalized with massive blood clots in both lungs and I'm lucky to be alive. About 6 months later the head buzz ended.  Any more, I only smoke as a social thing and still no head buzz after all this time.

Is there anyone that has experienced a lack of the head buzz?  Any explanation as to what might have caused this? 

Thanks for your input.