Change in the Home
Cats do not adjust well to change, so any type of change can cause anxiety. If you add a new family member or new pet, make sure to change your cat's routine as little as possible.
Introduce new members slowly. If it's a person, whether a new permanent resident or a guest, allow the cat to move at his own pace when it comes to interacting. If it's a new pet, keep the pets separated for the first few days, occasionally switching rooms so the pets can sniff each other's scent. Continue to have alone time with the resident cat so he doesn't feel like he has lost his place in your life.
If you move to a new home, put your cat in a safe room with all of his favorite things: toys, bowls, bed, litter box, scratch posts, etc. Once the rest of your stuff is moved to the new house, take him and his stuff and set it up similar to your previous residence. Setting up your furniture first will help him relax in the new environment. Keep his routine as consistent as possible during the move.
Loss of a family member can also cause anxiety. Animals also grieve losses. Give your cat something that smells like the family member to provide comfort. Try to reduce other stressors and keep the routine consistent to lessen the effects of loss.
Outdoor Stimuli
Cats can often be stressed by environmental factors happening outside their window. Loud parties or holidays such as July 4th can be very stressful since loud noises are scary for cats. A stray cat in the yard or dogs walking by may also cause stress.
During loud parties or holidays, keep your cat in a room at the back of your house where the noise is reduced. Keep windows closed and provide white noise such as a fan, radio and/or television. Try a cat DAP diffuser, which releases calming hormones that only pets can smell into the air.
If your cat is stressed by every day noises, move his perches away from windows. Keep blinds and curtains closed and encourage him to play and perch in calmer areas of your house.
Conflict between Pets
Sometimes, conflict between pets such as one cat terrorizing another or an obnoxious dog causes stress. If this happens, consider separating the pets or providing lots of escape routes for the victim cat.
Put a baby gate in front of a cat room so the dog can't enter. If you notice one cat bullying another, intervene and put the other cat in confinement for a few hours so the other cat can calm down.
Since cats are so dependent on consistency and routine, changes in the environment can cause quite a bit of stress. Being aware of this can help you prevent anxiety or solve it when it appears.