Accelerated Aging (IMAGE) University of California - Los Angeles Caption Chromosomes (stained blue) end in protective caps called telomeres (stained yellow) that are shorter in the elderly -- and in persons suffering chronic stress. A new UCLA study suggests cortisol is the culprit behind premature aging of the immune system in stressed-out people. Credit UCLA/Effros lab Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.