Cats are not very good at handling stress. When stress hits, it can cause a string of abnormal behaviors such as little box avoidance, withdrawal, depression, loss of appetite, aggression, and so forth.
Stress is also a trigger to many dormant illnesses that a cat may have. Many cats especially those that have lived in a shelter, Humane Society, or a rescue organization, are carriers of an upper respiratory virus. When they are under stress, the virus may become active and cause the cat to display signs of cat flu.
Also, when stress is the reason for litter box dysfunction, it usually signals urinary track infections which should be treated by a veterinarian.
Cause of Stress:
Most stress is a result of a change whether it is environmental, emotional or physical. A subtle change can be stressful to a cat. A substantial amount of changes can be devastating, such as moving to a new place, a new cat, another animal, spouse, a new roommate, a party, and so forth.
Noises and Smells:
Noises or unfamiliar scents can make a cat feel nervous and uneasy about their safety in the house. Cats are very sensitive to sound and smell. They are fearful of loud noises and would usually be very alerted when they hear a sudden, powerful sound. They may even immediately abort whatever they are doing in order to find refuge to get away from the loud noise which they identify as a potential danger.
When a place suddenly becomes rowdy for a period of time, it could create a tremendous amount of frustration to a cat. When the stress level goes beyond their tolerance, their behavior may change.
Cats use their strong olfactory sense to identify their location and investigate things they have contact with. If they have moved to a new place, the foreign smell may throw them off guard. That's why it is very helpful to take a personal item, such as their blanket, with them to the new house, so it will give them a feeling that they are at home.
New Cat:
Introducing a new cat to an established cat can be off-putting to the older cat since they have to re-establish position in the house. The older cat may feel invaded by the new cat's entry into its territory. Hissing and swatting may occur during the initial meeting with the new cat. The older cat may get jealous if it sees the new cat getting too much attention from the owner. Rivalry may transpire when the older cat and the new cat are vying for the top cat title in the house. All these factors can cause a range of stress to a cat. See How to Introduce a New cat to an Established cat for more details.
Loss of a Family Member:
Even though there is no solid evidence that cats [See Do Cat Cry Emotional Tears?] grieve over the death of a family member, there is a substantial amount of anecdotal evidence that cats become depressed by a sudden loss of a family member or being away from their human companion for a long period of time. Cat depression is reflected in loss of appetite, withdrawal, lethargy, and sometimes aggression.
Natural Remedies for Stress in Cats:
A natural remedy for stress should only be used, if the stress is NOT caused by an illness. Introduce one natural remedy at a time and consult your vet before trying any of the products: Top Natural Remedies for Stress in Cats.
Sources:
http://cats.about.com/cs/healthissues/a/stress.htm
http://cats.about.com/od/stressanxietyincats/tp/NaturalRemedies.htm
Image:
http://commons.wikimedia.org/wiki/File:Gustav_chocolate.jpg