Shaping personality functioning: type and timing effects of childhood maltreatment on personality functioning.

Personality functioning (PF) is a transdiagnostic construct central to contemporary models of personality pathology and a key mechanism linking childhood maltreatment (CM) to adult mental health difficulties. Yet the relative contributions of CM subtype, developmental timing, and cumulative exposure characteristics to adult PF impairment remain unclear. Gender-stratified conditional random forest regression was applied to data from a nationally representative German sample (N = 2,467; 51.8% women; mean age 50.7 years), simultaneously modelling year-specific CM timing, subtype, and cumulative indices against PF. PF was assessed with the Operationalized Psychodynamic Diagnostic-Structural Questionnaire Short Form (OPD-SQS), which demonstrated excellent external validity (area under the curve [AUC] = 0.89 for clinician-diagnosed personality disorder). Multiplicity, duration, and frequency of CM emerged as the dominant predictors of PF impairment in both sexes, substantially outperforming subtype-specific indicators. Among subtypes, emotional abuse, assessed via verbal abuse acts, showed the highest and most consistent variable importance across sensitive developmental windows, with sex-distinct timing patterns. Post-hoc analyses revealed threshold and interaction effects, underscoring that PF impairment is an environmentally mediated developmental outcome rather than a fixed individual vulnerability. These findings support routine PF assessment in individuals with CM histories and identify early adolescence as a priority window for preventive intervention.