Substance abuse can be a major contributing factor to child abuse. One U.S. study found that parents with documented substance abuse, most commonly alcohol, cocaine, and heroin, were much more likely to mistreat their children, and were also much more likely to reject court-ordered services and treatments. Another study found that over two-thirds of cases of child maltreatment involved parents with substance abuse problems. This study specifically found relationships between alcohol and physical abuse, and between cocaine and sexual abuse. Also parental stress caused by substance increases the likelihood of the minor exhibiting internalizing and externalizing behaviors. Although the abuse victim does not always realize the abuse is wrong, the internal confusion can lead to chaos. Inner anger turns to outer frustration. Once aged 17/18, drink and drugs are used to numb the hurt feelings, nightmares and daytime flashbacks. Acquisitive crimes to pay for the chemicals are inevitable if the victim is unable to find employment.