Dopamine D4 receptor (D4DR) and serotonin transporter promoter (5-HTTLPR) polymorphisms in the determination of temperament in 2-month-old infants

We and others have previously shown that the dopamine D4 exon III repeat (D 4DR) and the serotonin-transporter promoter region (5-HTTLPR) polymorphisms are not only associated with adult personality traits(1-7) but also with t emperament in P-week-old neonates,(8) We now report the results of a second study of these infants and their temperament at 2 months using Rothbart's Infant Behavior Questionnaire (IBQ).(9) There were significant negative cor relations between neonatal orientation and motor organization as measured b y the Neonatal Behavioral assessment Scale (NBAS)(10) at 2 weeks and negati ve emotionality, especially distress in daily situations, at 2 months of ag e. There were significant main effects for negative emotionality acid distr ess when the infants were grouped by the D4DR and the 5-HTTLPR polymorphism s. Infants with long D4DR alleles had significantly lower scores on Negativ e Emotionality (F[1.72]=8.50, P=0.005) and Distress to Limitations (F[1.72] = 4.93, P=0.03) than infants with short D4DR alleles, In contrast, infants with the short homozygous (s/s) 5-HTTLPR genotype had higher scores on Nega tive Emotionality (F[1.72] = 3.88, P = 0.053) and Distress to Limitations ( F[1.72] = 4.94, P = 0.029) than infants with the Vs or In genotypes, The st rongest effects occurred in those infants with the s/s 5-HTTLPR polymorphis m who also were lacking long D4DR alleles which in some studies has been li nked to adult novelty seeking,(1,6) These infants showed most negative emot ionality and most distress to daily situations, temperament traits that are perhaps the underpinning of adult neuroticism.