As you well know, stress can be very serious with cats. If they stop eating, then the fat mobilizes to the liver, and.....
It is important to note that the most common source of stress in a cat is changes in the environment. This can be moving, new roommate, different furniture, or even new outside cats - their sprays can be identified by the inside cats. Feliway spray is a phermone spray that can help reduce cat stress. The website is www.feliway.com
(I recommend the UK site over the USA site). Also during times of stress, increasing number of food bowls, water bowls, vertical perches and litter boxes can help reduce the stress of cats.
Hope that helps.