@caly420: That’s actually a myth. Interestingly it was started by women.
Here’s an excerpt from cracked.com : (yes, I know. I’m sorry)
“Why was the myth perpetuated? Most likely out of the embarrassment most mothers of pubescent boys feel. … It [probably] took you a few years to start looking and sounding like Powers Boothe. Consequently you had a fuzzy neck beard, and your parents didn’t want to be seen in public with you until you shaved it.
So instead of telling you straight up that you were a repulsive pock-marked abomination and having to hear you whine in your broken girly voice, they simply lied and told you shearing hair makes it stronger and thicker, knowing you would do it—and keep doing it—in a futile attempt look like Grizzly Adams.”