While the research into cat separation anxiety is just at the early stages of understanding, many have been noticing the signs.
Charlie was my future wife’s cat of 4 years. Some 6 years ago, when we moved in together, Charlie was aloof and prevented me, at least at first. Once she realized I was here to stay, she began accepting me. Initially, a bit stand-offish, but slowly accepting me to the point that she’d lay on my lap to the dismay of my wife. My job at the time was on the street, with periods of time in the home. We soon noticed that when I was away, Charlie would groom herself excessively, to the point of creating a bald spot on her flank. On my retirement, the only time we were off was every two weeks, my wife had to return to the hospital she worked for to do their citizenship. We would be off for 2 -3 days every 2 weeks. On our return, we would discover that Charlie had vomited all over the house, and on our bed. The reason we know this, once on birth in the home, we walked in on her vomiting. Whenever we brought out our suitcases to pack for our trip, Charlie would hide away, under the bed, the sofa, or under the dining table to avoid us.
Bubba, on the other hand, was a stray that I adopted about a year after I had moved in, my best guess was that he was about a year old. It took some time but Charlie and Bubba became good buddies. The only sign with him was on our return he would not let us out of sight. If you went to the bathroom, he had to be there. He would walk with me, rubbing up against me, to the extent as to almost trip me.
In doing research, all of these are signs of separation anxiety in cats. Some say being orphaned or being weaned early can predispose the development of separation anxiety. As this topic gets more study, there could be more information garnered.
Things to do are subjective. The first thing would be to get the veterinarian do a complete physical to make sure the behavior isn’t caused by some underlying physical issue. This will maybe involve blood work, urinalysis, thyroid testing, or a blood pressure test.
Some other suggestions include making the time of departure less stressful by making changes in the normal routine. Some experts suggest that for 15 minutes prior to leaving and upon return home, the operator should dismiss the cat. Leaving a distracting toy can be helpful. Someone suggested hiding yummy treats in various places in the home. Making the environment more stimulating may help. A kitty tower with toys attached close to a window could help. Sometimes they just enjoy seeing what’s going on outside.
Some experts have stated that in some situations the short-term use of anti-anxiety medications may be needed. You must be aware that these are not labeled specifically for use in cats and should / must be prescribed and monitored by your vet.