Children who have experienced abuse and maltreatment show changes in important parts of their brains. These changes are linked to depression, drug addiction, schizophrenia and other mental health problems, according to a new study from Harvard University. Professor Martin Teicher and his colleagues used magnetic resonance imagining technology (MRIs) to scan the brains of 193 participants ages 18 to 25 years old. Those who had been abused, neglected or mistreated had 6% less volume in certain areas of the hippocampus and reduced size in the subiculum region. Previous studies using laboratory animals subject to extreme stress found this causes their hippocampi to shrink in size. The researchers believe the same thing can occur in humans during two developmental periods in childhood --between ages three and five, and ages 11 and 13. The types of abuse the children had experienced were verbal, physical or sexual, physical or emotional neglect, bereavement, parental separation or parental discord. Their brain scans showed evidence of trauma, regardless of whether they had been diagnosed with a disorder. The hippocampus is associated with memory function. The subiculum receives information from the hippocampus and helps determine the individual's biochemical and behavioral responses to stress. Dr. Teicher believes that ongoing child abuse changes the way this "stress system" works and keeps it on "high alert." When it is in this broken state, a person feels anxious, fearful, and has trouble feeling joy or pleasure, which in turn leads to abusing alcohol and drugs. Dr. Teicher said that these brain changes can also cause mental illness, which explains why childhood abuse is linked to depression and schizophrenia. "By damaging it to some degree, you may cause the dopamine system to be disregulated, and disregulation of the dopamine system has been linked to drug abuse and psychological illness," he said. The study, the largest of its kind, was published in the Proceedings of the National Academy of Sciences.