The document summarizes three studies on factors related to child abuse and neglect. The first study found higher risks of sexual abuse in households with non-related parents compared to those with only natural or adoptive parents. The second study found a connection between abuse and ethnicity, with abused European-American children showing more aggression than non-abused children of the same ethnicity. The third study examined Munchausen syndrome by proxy cases in Japan and found most victims were male and the perpetrator was usually the biological mother.