Mental disabilities are okay to discuss the problem is the word "retard".
In this forum (I have found) and on many others the use of the word retard is considered distasteful and insulting to disabled people. Mentally "handicapped" is the new norm.
I reserve the word retard for the rare use only to describe republicans and overtly religious people. lol
As with any taboo subject, discussing a handicap is something private and should be treated with the utmost respect and decorum. When someone pours out their soul this can be later used as a weapon. Tread lightly and only trust a few.
Some of the most creative and smartest people also suffer with handicaps.