Abstract
Recent publications in the field of neurobiology related to personality disorders allow some consideration on the bidirectional relationship between genetically determined temperamental traits and environment, interactions observed in the normal development of personality during childhood and adolescence or on the contrary in the building of a disordered personality revealed at adulthood. Based on the review of studies about development of personality disorders in children, adolescents and adults, this article puts forward the interactive quality of relations between genetic background and environmental factors and proposes hypotheses concerning the role of temperament in the development of personality. Correlations between genes and environment (rGE) and interactions gene-environment (GxE) are examined. Bidirectional feedback between temperament and environment where individual temperamental characteristics determine environment selection or adjustment and not the opposite is an example of an interaction of evocative type. However, actual research designs face difficulties in the establishment of a causal link due to the multitude and complexity of involved factors linking personality traits with temperamental genetic markers. This might explain the emergence of an endophenotype concept as it has been used with autism. An endophenotype consists in a mesurable cognitive, neurophysiological or neurochemical variable expressing the genetic defect present before the onset of the illness. Some studies put forward possible endophenotypes for borderline, antisocial and schizotypal personality disorders. Longitudinal research has shown the predictive quality of externalized conduct disorders of childhood leading to antisocial and to a lesser extent borderline personality disorders in adulthood. Impulsivity and affective lability might be based on minor neurocognitive abnormalities, subclinical attention deficits and/or marked neuropsychological dimensions such as strong extraversion. Suboptimal serotoninergic regulation has been established in destructive impulsivity and suicidability. Abnormalities in the dopaminergic and noradrenergic systems might also be implicated but it remains unclear to what extent repeated trauma and abuse during childhood might modify the hypothalamic-pituitary-corticotropic axis in response to chronic stress and transform permanently the modulation of physiological and psychological reactions of these children to their perturbed environment. Researches on conduct disorders have also demonstrated the evocative interaction of a particular temperament with the environment responding to marked novelty seeking behaviour, hyperactivity, impulsivity and lack of proper physiological reaction to extreme stimuli. Lack of behaviour inhibition found in antisocial individuals is attributed to noradrenergic and serotoninergic abnormalities and neurocognitive deficits. The dimensional continuity of schizotypal personality to schizophrenia is well established and electrophysiological markers such as abnormal eye tracking movements, P300 evoked potentials, prolonged electrodermal reactions with cognitive disorganization and deficits in inhibition of attention to usual stimuli might be the future endophenotypical markers to schizophrenia susceptibility. Further studies on temperamental traits might lead to the identification of genetic markers as precursors to personality disorders.
Published Version
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