Separation anxiety is a disorder in which an animal panics when its primary caregiver is not present.  This can occur when all owners are completely out of the house, when the owner is absent and someone is still  present with the animal, or when the animal is merely separated from the owner, such as by a doorway.

The reason for this disorder is not completely understood, but separation anxiety is commonly seen in social species such as cats, dogs, birds, horses and primates.

Cats exhibit separation anxiety to a lesser visible degree than dogs.  Signs a cat is suffering from separation anxiety disorder are the following:
Urinating and defecating outside the litterbox, often on their owner's personal possessions such as on clothes or beds.
Becoming overly attached to owners and following them around the house.
Expressing anxiety as the owner prepares to leave or has already left, shown by increased vocalization, sulking and hiding.
Vomiting only in the owner's absence.
Excessive grooming, sometimes to the point of exposing skin.
Destructive behavior, such as tearing the owners clothes and personal possessions, or scratching on the door.
Loss of appetite.

If your cat exhibits any of these behaviors, postponed punishment is not the answer and can make matters much worse. Unless you catch the pet in the act of misbehaving and apply punishment at the moment of the act, there is little chance the pet will learn anything from the experience.  If punishment is given hours after the act was committed, it is likely the pet will become more anxious and fearful.

The first step to help your cat overcome separation anxiety is to take your cat to the vet for a complete check up since many symptoms can also signal underlying medical conditions.  It is best to rule out any physical problems before proceeding.

Basic behavioral management begins by the owner changing the way they interact with the cat.  Many owners reinforce anxious behavior without being aware of it.  If the cat is fearful or anxious, many owners reassure the pet by patting it and saying something like, "it's ok."  The cat sees this as acknowledgement of its anxiety.  As hard as it is to ignore all the attention seeking behavior and reward your cat for relaxed, calm behavior. Another key is to keep the arrivals and departures as low key as possible.  The general rule is to ignore your cat at least 15 minutes prior to leaving and arriving the home. Try leaving a radio or television on to provide a distraction while you are gone. 

In some cases medication may be necessary to treat separation anxiety.  With slight modifications you can ease your cats anxiety so the time you spend apart is less stressful and your time together is more enjoyable.