it is rare for kittens less than 4 months old to respond to the allure of catnip. so it has some connection to their hormones. at the same time even adult cats who have been fixed still adore it. my mother gives catnip to her very elderly cat to help relieve the pain of arthritis. in moderate amounts it is fine. it probably puts them in a state of temporary euphoria. when i have severe pain and i take medicine to relieve it, the sudden lack of pain gives me a sense of well being that is near to euphoria. the scent of the catnip, and there are several plants in this family that are related, mint family....horsemint grows wild here and cats treat it the same as catnip, in fact it is also called catmint. anyway the scent could be considered like aroma therapy. there are many websites out there that give lists of what plants are safe and what plants are not and i would google them and do some research before feeding plants to your cats as sometimes just one bite of a plant can kill your cat before you ever have time to take it to the vet...so it is best to be sure before you try it.