Personality disorder (PD) describes mental abnormalities that reflect long-term changes in cognition, emotion, and behaviour that affect mental functioning. PDs have been shown to be heritable, although research has not identified any consistent biomarkers associated with them. Biological research on PD is in a very early stage, and cannot be used as a basis for biological treatment. Current practices that favour aggressive drug therapy are not justified by the current state of research. Moreover, medications are often not effective for this patient population, while specific forms of psychotherapy have much better established efficacy.Keywords: personality disorder, heritability, neuroimaging, psychopharmacologyResumeLe terme « trouble de la personnalite » (TP) renvoie a des anomalies mentales attribuables a des changements a long terme dans la cognition, les emotions et les comportements qui nuisent au fonctionnement de l'esprit. Il a ete montre que les TP peuvent etre hereditaires, bien que les recherches n'aient pas cerne de biomarqueurs leur etant associes. Les recherches biologiques sur les TP en sont a leurs debuts et ne peuvent servir de base a un traitement biologique. L'etat actuel de la recherche ne justifie pas les pratiques favorisant la pharmacotherapie energique. De plus, la medication se revele souvent inefficace pour les patients souffrant de TP, alors que l'efficacite de certaines formes de psychotherapie a ete etablie.Mots-cles : trouble de la personnalite, heritabilite, neuroimagerie, psychopharmacologie.All mental disorders have neural correlates, and personality disorder (PD) is no exception. All mental disorders are also associated with heritable risk factors that play a role in their etiology (for a review, see Jang, 2005). Behaviour genetic methods compare concordance rates in monozygotic and dizygotic twins, allowing for quantitative estimates of heritability. They show that genes account for about half the variance in personality traits, as well as in PDs (Plomin, DeFries, Knopik, & Neiderhiser, 2012).The heritability of PDs has been demonstrated by large scale behaviour genetic studies (Reichborn-Kjennerud, 2010; Torgersen et al., 2002; Torgersen et al., 2012). Thus, borderline personality disorder, for example, which was long thought to be an environmental condition, has a single heritable factor that accounts for 55% of the variance in all nine of its DSM-5 criteria (Reichborn-Kjennerud et al., 2013). These studies also showed that the level of genetic influence is in much the same range as for personality traits. The precise nature of these heritable factors remains unknown.These findings confirm that PD is not a simple, direct consequence of bad parenting or child abuse, but is rooted in interactions between an abnormal temperament and an adverse environment. Even when a disorder is heritable, it does not necessarily develop unless environmental stressors are also present (e.g., Rutter, 2006). Thus, the effects of biology always have to be understood in the light of their interactions with a psychosocial context: Genes bend the twig, but do not determine the shape of the tree.Genetic influences can also be measured by temperament, defined as the heritable aspect of personality, present a birth, which is then shaped by experience into stable traits, and can be amplified to pathological levels by psychosocial adversity (see Rutter, 1987). A vulnerable temperament tends to make the development of a PD more likely, and determines the type of PD that can develop. This principle applies to all PDs: For example, highly introverted people will rarely develop narcissistic PD, and a highly extraverted person would not develop avoidant PD (Paris, 2003).Some of the most important effects of heritable factors in psychopathology lie in individual differences in susceptibility to environmental risks. People who are highly resilient can be surprisingly unaffected by serious life adversities (Rutter, 2012). …