[The genetics of child temperament]. / Genética del temperamento en niños.

INTRODUCTION: In spite of the high initial expectancy in preliminary results concerning the genetics of personality, these studies have not provided satisfactory results. The failure could be related to the lack of biological validity of personality concept and the important influence of environmental factors on personality. A possible way to solve this problem is to look at the temperament of preschool children. It is expected that variability in infants' behaviour can be better defined and with less environmental influence. DEVELOPMENT: Firstly, twin and adoption studies of child temperament in comparison with the studies of personality in adults are reviewed. Secondly, the molecular association studies carried out concerning child temperament are analyzed. The serotonin transporter gene (5-HTT), D4 receptor gene (DRD4) and mono amino oxidade-A gene (MAOA) have been considered candidates to explain variability in child temperament because these genes have been related with specific personality dimensions and mental diseases. Finally, the methodological problems and the future direction of research in this field are considered. CONCLUSIONS: Heritability shows higher values in infant temperament than in adult personality. Different gene polymorphisms on 5-HTT, DRD4 and MAOA could explain some individual variability in children's behavior, although replication studies are needed to confirm the role of these genes. Longitudinal studies in large samples that include gene and environmental interactions are one of the best ways to improve our knowledge about the genetics of child temperament.

Genética del temperamento en niños / The genetics of child temperament

A pesar de que inicialmente dio resultados esperanzadores, el estudio de las bases genéticas de lapersonalidad no ha logrado unos resultados satisfactorios. Las razones básicas han sido la cuestionable validez biológica de las dimensiones de la personalidad y la importante contribución del ambiente. Una alternativa ha sido recurrir al estudio deltemperamento en niños (lactantes y preescolares) en los que la variabilidad del comportamiento individual está menos modulada por factores ambientales. Desarrollo. En primer lugar se presentan los estudios de gemelos y de adopción, que determinan el grado de heredabilidad del temperamento en niños, y se comparan con los estudios de personalidad en adultos. Seguidamente se pasa a comentar los estudios de asociación realizados con el fin de identificar los genes que intervienen en las basesmoleculares del temperamento en niños, principalmente los estudios relacionados con el gen transportador de serotonina (5-HTT), el gen receptor (DRD4) y el gen monoamino oxidasa A (MAOA), relacionados con dimensiones específicas o trastornos de la personalidad. Por último, se analizan las futuras direcciones hacia las que se dirige este campo de investigación.Conclusión. La investigación del temperamento en niños presenta una heredabilidad más elevada que la personalidad en adultos. Los polimorfismos de los genes 5-HTT y DRD4 contribuyen a explicar parte de la variabilidad observada en el comportamiento individual. Aun así, la falta de replicabilidad en los estudios actuales hace necesarios nuevos enfoques, y son particularmente relevantes los estudios longitudinales que introduzcan la investigación de las interacciones geneticoambientales

In spite of the high initial expectancy in preliminary results concerning the genetics of personality,these studies have not provided satisfactory results. The failure could be related to the lack of biological validity of personality concept and the important influence of environmental factors on personality. A possible way to solve this problem is to look atthe temperament of preschool children. It is expected that variability in infants’ behaviour can be better defined and with less environmental influence. Development. Firstly, twin and adoption studies of child temperament in comparison with the studiesof personality in adults are reviewed. Secondly, the molecular association studies carried out concerning child temperament are analyzed. The serotonin transporter gene (5-HTT), D4 receptor gene (DRD4) and mono amino oxidade-A gene (MAOA) have been considered candidates to explain variability in child temperament because these genes have been related withspecific personality dimensions and mental diseases. Finally, the methodological problems and the future direction of research in this field are considered. Conclusions. Heritability shows higher values in infant temperament than in adult personality.Different gene polymorphisms on 5-HTT, DRD4 and MAOA could explain some individual variability in children’s behavior, although replication studies are needed to confirm the role of these genes. Longitudinal studies in large samples that include gene and environmental interactions are one of the best ways to improve our knowledge about the genetics of child temperament