Sibling abuse includes the physical, psychological, or sexual abuse of one sibling by another. More often than not, the younger sibling is abused by the older sibling, however this is not always the case. Sibling abuse is the most common of family violence in the US, but the least reported. As opposed to sibling rivalry, sibling abuse is characterized by the one-sided treatment of one sibling to another. Sibling abuse has been found to most commonly occur in dysfunctional families where abuse from parents is present. In the US, 40% of children have engaged in physical aggression towards a sibling, and as many as 85% of children have engaged in verbal abuse towards their sibling. Types and prevalence Physical abuse Sibling physical abuse is defined as a sibling deliberately causing violence to another sibling. The abuse can be inflicted with shoving, hitting, slapping, kicking, biting, pinching, scratching, and hair-pulling. Sibling physical abuse is more common than peer bullying and other forms of family abuse, such as spousal or child abuse, though for a multitude of reasons, it is very difficult to calculate exact prevalence rates. Even when sibling abuse is recognized it remains heavily under-reported, due to the lack of resources provided to families, such as child protective services and mandatory reporters. Professional childcare providers have considerably different definitions of the term, and lack a system to track reports. Sibling physical abuse persists from childhood through adulthood, with prevalence rates varying across studies, though its intensity and frequency declines as the victim and/or perpetrator grow up. Sibling aggression is somewhat common even in families that could not be classified as pervasively abusive, with 37% of 498 children committing at least one act of serious abuse during the previous year; in abusive families, 100% of children committed at least one act of serious abuse. In Pakistani immigrant families in the UK, siblings have the highest proportion of physical abuse compared to other family members, with 35% being done by siblings, compared to 33% by mothers and 19% by fathers. Several studies show that sisters are more likely to be victimized by brothers than vice versa. Additionally, age is also a contributing factor to sibling abuse, where older siblings are more likely to abuse the younger siblings. Psychological abuse Psychological abuse among siblings is even more difficult to identify. Psychological abuse in siblings can be identified by both the frequency and intensity