Insular volume reduction in patients with major psychiatric disorders experiencing parental versus peer-related childhood adversity

Adverse childhood experiences (ACEs) have been linked to structural brain alterations, yet most MRI studies examine single diagnoses and rarely distinguish adversity arising from caregivers (“vertical”) versus peers (“horizontal”). A total of 156 inpatients — 76 with major depressive disorder, 45 with schizophrenia, and 35 with bipolar disorder (mean age=35.3 ± 11.8 years; 55.1% male) — underwent T1-weighted MRI. ACE counts were rated with the Retrospective Chart Review-based Assessment Scale for Adverse Childhood Events and Experiences (RC-ACEE) based on information extracted from discharge summaries. Canonical ACE-sensitive regional volumes (anterior cingulate cortex, insula, hippocampus, amygdala) were calculated using FreeSurfer 7.2. Greater ACE counts were associated with smaller left insular volume (Bonferroni-corrected p = 0.032), with no significant interactions by diagnosis or sex; diagnosis-stratified analyses showed this association in major depressive disorder and schizophrenia but not in bipolar disorder. In exploratory models, vertical ACE counts were related to smaller left insular volume (p = 0.013), while horizontal ACE counts were not (p = 0.081). These findings suggest that cumulative adversity is associated with reduced left insular volume across disorders, supporting the hypothesis that the insula may represent a transdiagnostic neural correlate linking childhood adversity to psychiatric symptoms.