In the late 1960s, some researchers reported catnip gave people a marijuana-like high, but it turned out they had simply mixed up the two plants. As veterinarian Arnold Plotnick of Manhattan Cat Specialists in New York wrote to me in an email, "Think about it… catnip is cheap and legal. If it had a significant effect on people, everyone would be smoking it."
Meanwhile, cats do feel effects from marijuana, but it may be scary for them. "Animals can't understand they're being intoxicated, therefore it can cause considerable anxiety," says Bruce Kornreich, associate director of the Cornell Feline Health Center in upstate New York.