Mentally disabled is also a term that is abused nowadays. I have anxiety, I'm depressed, I'm stressed. Here's some pills and a note to sit home and collect disability (my aunt does it). It's not a mental disability, it is called LIFE! Get the fuck over it.
Mentally disabled are the people who work in my local Burger King. They do not have the mental capacity to do much more than flip burgers and clean, yet they are glad for the job that they have, and frankly, do better than most fast food employees.