[Towards an integrative understanding of complex trauma]

The body of knowledge on trauma is rapidly expanding. Since 2022, the WHO has been calling for the history of adversity to be systematically taken into account when assessing the state of health of all individuals. But at this stage, our understanding of the precise mechanisms of complex trauma remains incomplete. In fact, its pathophysiology lies at the crossroads of neurobiological, psychological and relational fields of study. The aim of this review is to set out the key elements of this scientific literature in order to move towards a more global and comprehensive vision, which remains a challenge. The clinical forms of complex trauma are analyzed in the light of the neurobiology of chronic and early stress, cognitive-emotional disorders, and relational and attachment imbalances. Four dimensions each play a major role in the psycho-traumatic equation: characteristics relating to adversity factors, circumstances of onset, any prior vulnerabilities, and environmental resources (particularly relational support). Borderline personality disorder appears to be one of the faces of complex trauma, and a valuable model for understanding a pathophysiology that takes place in two stages, in which previous psychobiological changes contribute to the disproportionate or unrelated appearance of symptoms in relation to current environmental factors. This pathophysiology of a profound link between early experiences, alterations in the self and affective regulation disorders in adolescence or adulthood, raises new questions about the definition and understanding of psychiatric disorders, and first and foremost personality disorders, which are at the crossroads of the shift from "simple" trauma to complex trauma. Understanding the mechanics of trauma ultimately involves a shift from a symptom-centered approach to a dual approach involving the symptom in a synchronic (instantaneous) perspective and the patient's history in a diachronic (temporal evolution) perspective. It is also a shift from the subject to his or her environment, which calls for a global and systemic vision.