The goal of this clinical trial was to learn about the effect of maltreatment on psychological and brain characteristics in a group of children. The main question it aims to answer are: which are the clinical characteristics of maltreated children before and after a psychological intervention? what changes in brain emotional processing after a psychological intervention? and what is the effect of serotonin transporter variants after a psychological therapy? Participants were assessed before and after intervention with:

• clinical measures of anxiety, depression post-traumatic stress and callous-unemotional traits
• functional neuroimaging techniques to measure brain activity.
• A sample of buccal epithelial cells to obtain information on serotonin transporter.

Researchers will compare maltreated children with a group on non-maltreated children to see if there are differences on psychological characteristics and on brain activity before treatment.

Participants Twenty-five children who suffered child abuse were initially referred by a non-governmental shelter in Mexico City. Children were removed from their homes and placed at the shelter because one or both parents were undergoing judicial processes for various crimes, including child abuse. None of the children had ever received psychological therapy because the shelter did not have a protocol for psychological intervention. After a thorough search for the most appropriate therapy, the TF-CBT was chosen. The information was shared with the shelter administrative board. Once authorities and health professionals at the shelter were informed about the aim of the study, they agreed about the appropriateness of the intervention. A group of trained psychologists would apply the TF-CBT as part of the research protocol. Only children who met the inclusion criteria would participate. Parents or primary caregivers gave their informed written consent for their children to participate in the study. Ethical approval of the study was granted, and the research was performed in accordance with the Code of Ethics of the World Medical Association Declaration of Helsinki.

The final sample consisted of an experimental group of 14 MC which included 4 boys and 10 girls (mean age = 8.77 years old, S.D.=1.83), who had experienced a positive history of different types of trauma, and a control group of 10 HC from the general population who were developing normally and were age-matched to the MC (4 boys and 6 girls) (mean age = 9.57 years old, S.D. = 1.91). They were recruited through an advertisement placed at the Faculty of Psychology, National Autonomous University of Mexico UNAM or by direct referral from parents of previous participants in other studies. All were residents of Mexico City. The study protocol was conducted with the approval of the UNAM Institutional Review Board.

Clinical scales A comprehensive clinical battery was used to assess all participants through the administration of the following assessment tools: The Child Depression Inventory-CDI Spanish version. The Spence Children's Anxiety Scale-SCAS standardized on a sample of Mexican children, the Child PTSD Symptom Scale-CPSS Spanish version, and the Inventory of Callous Unemotional Traits-ICU Spanish version.

Procedure The MC group was assessed before and after the implementation of Trauma Focused-Cognitive Behavior Therapy TF-CBT using clinical scales and an emotion paradigm through functional magnetic resonance imaging fMRI. The HC group was also assessed and scanned twice.

Of the total sample, 14 MC completed the TF-CBT modules and came in for their post-treatment assessment session. In addition, the 10 HC who, according to their parents, had not completed any type of psychological intervention during those 4 months, and still met the inclusion criteria for the initial control group were selected and returned for their post-evaluation session.

Inclusion Criteria:

For maltreated children group (MC)

• Ages between 7 to 12 years old
• History of trauma or abuse
• Symptoms of Post traumatic stress disorder
• Symptoms of anxiety

For healthy control (HC)

• Ages between 7 to 12 years old
• No history of trauma or abuse
• Absence or low symptoms of Post Traumatic Stress Disorder
• Absence or low symptoms of anxiety

Exclusion Criteria:

• Any neurodevelopmental, medical condition or risk factor other than maltreatment.

There is no plan to share any data.