I bought a harness and lead for my young cat. The idea was to take him outside safely. He changed when I put it on. He is normally very active in the morning. I put the harness on him and he calms down. It is like someone gave him an injection. I don’t know what is happening.
The harness is a bit like a coat but not as big. I like it because it makes him calmer. In the morning he runs around a lot. I am not sure I like it. He could get hurt. He could damage something.
I am not sure he should wear it as it changes him so much. The change is a bit of a shock to me and strange to see.
Do you know why a harness for a lead changes him so much?
Response from Michael: I hope people comment on this. You have probably heard of the Thundershirt. This a product mainly for dogs but also cats. It calms them down. It is usually bought by dog owners whose dog has anxiety problems or becomes overexcited under certain situations. The general opinion is that is works but not always and, here’s the 64,000 dollar question: How does it work?
It seems to me that the harness you have bought works like a Thundershirt. It wasn’t designed to but it does. So it is triggering something inside your cat.
You say it is as if he has been given an injection. This may indicate that wearing the harness triggers the production of a hormone or a brain chemical of some sort in the cat. It may trigger the production of a certain type of neurotransmitter in the brain.
The manufacturers say the pressure calms the animal. Why? It may trigger an emotional connection to the time when the cat was a kitten being nursed by his mother. The pressure of the harness may create a reassurance in the cat for that reason. It may also cause some confusion because it is a created feeling and not real. In other words it puts the cat out of character for his age.
I also wonder if this reaction will continue or will it wear off? It may. I have not read that the Thundershirt stops working after a while but it might become less effective during long usage.
I’d be interested to know what anyone else has to say on this phenomenon. Update: I believe the cause for the change in personality is a partial kitten response. This is the response cats/kittens make when picked up by the scruff of the neck. This is strange because the harness does not put pressure on the back of the neck.

Hello Laurel, thank you for commenting and asking. Are you sure that your young cat’s jumping and biting on your older cat is because he was weaned early? It may be because he is a young cat who wants to play rough which of course as you know is normal for cats of that age.
I have not seen a connection between early weaning and aggression, as I recall. I will doublecheck that but I don’t recall a connection between the two. On just reading your comment what comes to mind more readily is his age and the desire to play fight which is not something that your older cat wants to engage in. Apparently, however, early weaning can lead to a cat wanting to play more than normal and of course play, as mentioned, includes biting.
https://pictures-of-cats.org/Mother-Kitten-Relationship.html
I raised a kitten from seven weeks of age and he is now around four years of age and he still likes to jump on my feet and bite because he wants to play in a very rough way. He is expressing a desire to hunt which he can’t do as much as he wants because he lives in an enclosure albeit a very large garden enclosure.
I don’t think that there is an easy fix for this “problem”. I don’t think it is practical to train it out of him. It seems to me that there is an incompatibility between the older and younger cat as they have different desires. These are just thoughts.
We recently adopted a kitten who was taken away from his mother and litter too early. He jumps on and bites our older cat who growls and tries to fight back. She is clearly frustrated and sad. When I put the younger kittens harness on him, he calms down and doesn’t go after the older cat with as much aggression. But I’m concerned that it’s dwarfing his energy and personality. I feel so bad for my other cat, but he needs to learn not to attack her. thoughts???
Nice to hear that. I think Ruth was correct. The harness on a cat somehow triggers the ‘kitten response’ – the response of the kitten to go limp when the mother picks him up by the scruff of the neck. Only the harness hardly touches the neck. It completely alters the way my cat behaves. He looks non-plussed. Zonked out. Weird.
I’m not sure why a harness would calm a cat,but my dog was easier to walk and a lot calmer with a harness than collar and leash. The harness is not going to hurt the cat. And since we have denied access to the outdoors to cats for various reasons,”walking” them is an adjustment some cats may accept so they can be outdoors.
Yes all those things are unnatural to them too, but long ago humans domesticated cats and we can’t turn the clock back now and leave them in the wild where they belonged, it’s too late!
All we can do is the best we can for our own cats and for cats worldwide and this is what I do.
But canned cat-foods, human’s houses, being kept by humans, humans, and all other things “human” are not alien and unnatural to them. Oh, okay. Got it.