At what age do they usually respond to catnip?

I was under the impression that kitties don't react to catnip until the second half of their first year. Well, today I got my order from Ragtime Collars, and she included a cute little catnip mouse. I gave it to the kittens and 4mo Blue went NUTS!!! I have never seen her so ferocious - that poor mouse! I haven't bought any catnip yet (Delilah never cared for it), so I'm wondering if I should get some more of these amusing toys, or was it more likely just a coincidence? Blue reeked of catnip when she was done wrestling that mouse!

I put out catnip occasionally on my cats' scratchers and this weekend was the first time my little babies (4 months) had a reaction to it, so I think that might be the average age. Aren't kitties hilarious to watch? imagine 12 kitties rolling around my living room in catnip bliss

I've seen cats young and old respond to it, not sure there are specific ages

It has been said that kittens dont react to catnip until at least 6 months old. Well I proved them wrong....lol Kricket at 2 months found Roxys catnip toy and had a field day with it. She didnt know if she was coming or going.

I'm not sure that age has anything to do with it, since cats younger than six months have responded to catnip. But 50% of cats don't respond to it at all and this is quite normal.

My babies responded to catnip around 4 months old, they love it. I buy one of those containers of catnip and then I fill an old sock with some, tie a knot so it doesnt come out, and the kitties love playing with the catnip sock.