Original: Incest between adults and prepubescent or adolescent children is considered a form of child sexual abuse that has been shown to be one of the most extreme forms of childhood trauma, a trauma that often does serious and long-term psychological damage, especially in the case of parental incest.
Simplified: This form has been shown to cause one of the worst forms of childhood trauma, a trauma that often causes serious and long-term psychological damage, especially in the case of parental incest.