The long forms of the dopamine D4 receptor (DRD4) exon III repeat polymorphism (L-DRD4) have been linked in some studies to the adult personality trait of novelty seeking (NS), as well as to infant personality traits related to interest and activity. The current investigation extends the results of our previous longitudinal study on 1- to 5-month-old neonates assessed by the Early and Revised Infancy Temperament Questionnaire (EITQ/RITQ), in which we found a significant correlation between the DRD4 polymorphism and the adaptability trait at 1 month of age. In this study, we examined the relationship between children's behavior at 3 years of age, measured with the Toddler Temperament Scale (TTS), and DRD4 exon III repeat polymorphism. We found a significant association between the behavioral dimension of intensity of reaction and DRD4 genotypes. Current data failed to confirm the association with the adaptability trait. None of the extraversion and/or exploratory behavior measures was related to the L-DRD4 allele, as expected. In contrast, children with 4/7 genotypes showed worse response to new stimuli compared with 4/4 genotypes. This study corroborates only in part previous results on the link between the DRD4 gene and human temperament.
We have examined the relationship between the common dopamine D4 receptor (DRD4) exon III repeat polymorphism and infants' behavior measured with the Italian version of the Early and Revised Infancy Temperament Questionnaires (EITQ/RITQ) in 122 Italian neonates at 1 and 5 months of life, when the genetic contribution to the behavior can be more clearly assessed. Two-way (genotype x age) analysis of variance revealed a significant correlation with the temperamental subscale of adaptability [F(1, 120) = 5.26, P < 0.02]. At 1 month of life (early assessment), infants with long (L) DRD4 alleles presented significantly low scores (L 2.61 +/- 0.073; S 2.84 + 0.79; Newman-Keuls P = 0.03) in comparison with the high scores of infants with short (S) alleles (L 2.4 +/- 0.059; S 2.25 +/- 0.57). These differences were not detected at 5 months of life (late assessment), denoting a strong environmental effect at this age on the genetic background. These results confirm and extend the genetic influence of the DRD4 gene in human temperament at birth.
This study attempted to determine how cognitive, motor, linguistic, and social competencies of preterm children develop from birth to five years in comparison with a group of fullterm children. The interaction between biological and social risks was considered in evaluating short- and long-term delays in development. The study was also designed to ascertain whether infant test scores of the first two years are predictive of later IQ scores. A total of 195 healthy Italian preterms (birthweight ≤ 2000 grams, without severe neonatal complications) were administered the Brunet-Lezine test at 6,12, and 24 months (corrected age), and 149 of them the Stanford-Binet test at 3,4, and 5 years (chronological age). The preterm group showed motor, cognitive, and social delays in the first year, linguistic delays until 24 months, and general cognitive delays until 5 years in comparison with the fullterm group. However, preterms' mean infant test scores and IQ scores fell within the normal range. The probability of delays in development was increased by the conditions of intra-uterine growth retardation and very-low-birthweight, and, after the first year of life, by a low level of paternal education. Brunet-Lezine test scores were predictive of later IQ scores, as were sex and parental education. In conclusion, preterm birth is correlated with delays in development, especially when it is associated with other biological and/or social risk factors.
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