It doesn't make you lazy. It's just that when you're stoned, you realize that it's just not worth the effin' effort.
Seriously though, I've known a lot of pot smokers in my life, and only ONE schizophrenic. He never smoked pot.
This study is bogus. There are an awful lot of pot smokers and former pot smokers in America, and I'm sure there are a very small number of schizophrenics.