To Örebro University

Introduction: Neuroimaging studies have linked early childhood stressors such as maltreatment or neglect to abnormal brain development. However, little is known regarding the long-term neurobiological consequences of more moderate, yet prevalent stressors such as peer victimization.

Method: 84 healthy adolescents from the Southern California Twin Register at USC were included in this study. Peer victimization was assessed at ages 9 using a Child Friendship Questionnaire, and scores for all items were averaged to create a mean score for peer victimization. 3D high-resolution T1-weighted anatomical images were collected at age 14 on a 3T Siemens Magnetom Trio scanner at the USC DCNI Center. Cortical thickness was estimated using FreeSurfer (any error corrected manually) and amygdala volumes were obtained through manual segmentation. Mixed effects regression models were used to assess the correlation between peer victimization and brain measures, while controlling for whole brain volume and subject relatedness.

Results: Peer victimization at age 9 was significantly correlated with thinner cortex in the bilateral anterior temporal lobes, left medial temporal gyrus, left inferior temporal gyrus, and lateral prefrontal regions at age 14, however only for females and not males. On the other hand, peer victimization at age 9 was significantly correlated with enlarged amygdala bilaterally at age 14, however only for males and not females.

Conclusion: We found peer victimization to be associated with structural abnormalities in stress-sensitive brain regions including the frontal cortex, temporal lobe, and the amygdala. Findings further suggest that neurodevelopmental consequences of peer victimization may be different for males and females.