Article on the physical and pychological effects of stress - it's meant for humans but, as we all know, pet parrots live with stress all their lives due to the incredibly unnatural conditions they are kept in captivity so extrapolation is perfectly acceptable. And to make it 'even', I am also giving you the second link that says that, if you are stressed out, feeding birds help! Not that this is really shocking to us, is it?
https://www.zmescience.com/medicine/eff ... -242789930
https://www.brownsvilleherald.com/onlin ... cdae5.html