What is the Cinderella effect?

The Cinderella effect is a term used by psychologists to describe the high incidence of stepchildren being physically or sexually abused, neglected or murdered, or otherwise mistreated at the hands of their step parents at a significantly higher rate than their genetic counterparts. It takes its name from the character Cinderella from the fairytale, who in the story was cruelly treated by her stepmother and stepsisters.