I used this term "mentally disturbed" in my complaint letter to the head librarian. I wonder what does this term "mentally disturbed" mean to the native English only speaking ears. You see, I borrowed this one book from a library, and I returned it before its due date. Then later, I got an overdue notice saying that I still possessed an outstanding library book. So I went down to the library, showed one of the clerks the overdue notice, and explained to the person that I already turned in the book and that I didn't have that book anymore. So that person asked another helper to locate the book on the bookshelf. I waited and then the helper showed up with the book that I borrowed. They talked among themselves about what to do. Then they said that I still owed them the fine for the book. They insisted that it was possible that I put the "overdue" book back on the shelf myself. I still maintained that I did not shelf that book and that I returned the book some weeks ago. They said if I wanted to dispute the fine, I should write to the head librarian. Since I had a headache and was emotionally annoyed at the time of quarrel, I decided to use the term "mentally disturbed" in this context "I was mentally disturbed when they accused me that I shelved the book myself."