Child-on-child sexual abuse is a form of child sexual abuse in which a prepubescent child is sexually abused by one or more other children or adolescent youths, and in which no adult is directly involved. The term has been defined as sexual activity between children that occurs "without consent, without equality, or as a result of coercion". This includes when one of the children uses physical force, threats, trickery or emotional manipulation to elicit cooperation. Child-on-child sexual abuse is further differentiated from normative sexual play or anatomical curiosity and exploration (i.e. "playing doctor") because child-on-child sexual abuse is an overt and deliberate action directed at sexual stimulation, including orgasm. In many instances, the initiator exploits the other child's naïveté, and the victim is unaware of the nature of what is happening to them. When sexual abuse is perpetrated by one sibling upon another, it is known as "intersibling abuse".
In the etiology of child-on-child sexual abuse, young children who have not matured sexually are incapable of knowing about specific sex acts without an external source. Consequently, children who initiate or solicit overtly sexual acts with other children most often have been sexually victimized by an adult beforehand, or by another child who was in turn abused by an adult. More than half have been victimized by two or more perpetrators. In some instances, the perpetrating child was exposed to pornography or repeatedly witnessed sexual activity of adults at a very young age, and this can also be considered a form of child sexual abuse.
In other cases, a child or adolescent may have no intent to cause any harm to another child, and he or she acts merely on a passing impulse. However, this act may still result in harm to the another child and is a form of child-on-child sexual abuse. 
The incidence of child-on-child sexual abuse is not known with any certainty, similar to abuse by adults. It frequently goes unreported because it is not widely known of in the public, and often occurs outside of adults' supervision. Even if known by adults, it is sometimes dismissed as harmless by those who do not understand the implications. In particular, intersibling abuse is under-reported relative to the reporting rates for parent-child sexual abuse, and disclosure of the incest by the victim during childhood is rare.
Major factors that affect the severity of symptoms include the use of force or coercion, the frequency of the abuse, and the invasiveness of the act. An increased risk of victimization later in life has also been reported.
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