lake Why don't I get a buzz from catnip?

I haven't smoked it since 2007, and back then when I mixed it with tobacco it gave me a pretty decent buzz (not a high, just a buzz) for about an hour and a half. I would smoke one small bowl and that would be enough to give me a good buzz. But I just started to smoke it again and now it doesn't even give me the slightest buzz at all. I smoked 2 big bowls mixed with tobacco and got nothing at all. Why would it have effects back then and now have no effects?there