Like human beings, cats can also suffer from stress, but they usually communicate it by demonstrating a change to their normal behaviour patterns. Taken to an extreme, this can ultimately affect their overall health as it sometimes has an impact on their immune system, making them more prone to picking up infections that they would normally be able to fight off. Cats are mainly creatures of habit, and do not welcome a change to their routine, however slight it may seem to you as their owner. They will usually adapt to a minor change, or learn to live with it, but it is the longer-term causes of stress that may need to be addressed.
The most common causes of stress are those that affect a cat's feelings of safety and security. This may include situations like a move of home, the introduction of a new pet, the arrival of a baby in the household, threats from a neighbouring cat, unfamiliar human visitors (especially if they stay for a few days or longer), noisy neighbours, the intrusion of builders, or even a change to the layout of your home. Many cats are very sensitive to the feelings of their owners, and if you are feeling very stressed with maybe family or work problems, your cat may sense this and pick up on your emotions, and your distress could be transmitted to your pet.
Cats can display stress in a number of different ways, but you will usually see a change in their routines. Those that are normally very independent may come to you for reassurance and demand more attention that usual, wanting to be picked up and cuddled, or following you round the house, when they would usually sit and monitor the situation from the comfort of their own bed. On the other hand, cats that are normally affectionate lap-cats may react by viewing you with suspicion as the instigator of the change that has upset them, and will be completely 'standoffish' instead. Even those that are usually very placid will sometimes react by growling and hissing if they are frightened or upset, and may try and scratch or bite you or your other pets. If it is a problem indoors that is bothering them, they may spend far more time outside in order to avoid the situation, even wanting to be fed out of doors. On the other hand, if they are being bullied by another cat in the garden, they may refuse to go out at all, and might even resort to relieving themselves in a quiet corner of a room, rather than going out if this is what they would normally do. Sometimes cats that are upset by a change to their routine will refuse to eat at all, or may develop some kind of skin problem or other infection. Any physiological change like this should be taken seriously, and it is important to take your cat to the Vet as soon as possible so that you can discuss the appropriate remedy.
Research into the behaviour of many species (including humans and cats) indicates that the natural coping strategies to stress are formulated during the very early stages of life, and can be influenced by parental reactions and surroundings. In the case of cats, a nervous mother cat may well pass on her fears and anxieties to her kittens, and if you adopt a nervous cat it will be important to try and work out what they are frightened of so that you can provide a relatively stress-free environment. If you can gain their confidence, it will help if they can start to see you as a stress reliever rather than someone who makes things worse, but this will take many hours of patience. If you are a breeder, you can help potential future owners of your kittens by ensuring that they are thoroughly socialised at an early age, and are accustomed to the normal household sounds, as well as coming into contact with other people and pets. Stress can also be caused by boredom, and so if you think this may be the cause, make sure that you cat has plenty of toys to play with and stimulate their minds. If you are out and your cat does not have a companion, it may be worth considering getting another cat, although this could initially increase the levels of stress before it helps to relieve them.
The simplest answer to this would be to remove the cause of the stress, but of course, this is often not possible. If the root of the stress is short term, you should try to help your cat realise that they you still love them very much, pay them extra attention and maybe tempt them to eat with some special food. Situations that fall into this category include building work (which will eventually finish), and even a new baby or an additional new pet as sooner or later your cat will come to accept the newcomer as being inevitable! In the meantime, a plug-in diffuser such as Feliway may help to calm your cat's nerves. With longer-term problems, such as your cat being bullied by a neighbour's cat that either comes through your cat flap, or encroaches onto your garden, you may need to re-think your cat's lifestyle as you do not want them to live in a state of terror. It may be necessary for your cat to become an indoor cat, with the cat flap locked (or removed), and the possibility of a litter tray indoors. If your cat still seems intent on going out, maybe you could go out at the same time, to make sure that he is not attacked by any marauders. The ultimate remedy is to ask your vet to prescribe tranquillisers for your cat, but this is not a good long-term solution, as there may be underlying side effects - and it is also just dealing with the symptoms rather than with the cause. They key to managing feline stress is to know your cat, and learn to recognise when all is not well. Quite often reassurance and attention will be the key, but unfortunately this may not resolve all cases of stress, and you may need to discuss the options with your Vet. It is important to address the issue of stress so that your cat can return to living a happy and relatively peaceful life, but this may take considerable effort on your part to help your beloved pet overcome whatever is making him unhappy.