8. “Multiple personalities” is just for movies now

Multiple personality disorder has not been considered a legit psychiatric diagnosis since 1994, but it’s an idea that persists in pop culture. The closest thing is what’s known as dissociative identity disorder , characterized by a sense of detachment from your own emotions.

The idea that a person can “split” their personalities, with each being unaware of the others, was popularized by the 1973 book (and later movie) Sybil . The book was supposedly based on a true story, but the woman it was based on has said that the multiple personalities were not real .