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The S allele of the 5-HTTLPR has been associated with anxiety-related behavioural traits and harm avoidance. The 5-HTTLPR polymorphism is suggested to modulate the serotonergic response to stress, meaning that individuals carrying the SS genotype who have significant stress histories may tend to develop depressive symptoms. In the Mannheim Study of Risk Children, which followed a cohort of n = 384 from birth to adolescence, the association of 5-HTTLPR with harm avoidance and internalising problems was examined, including gender and early life stress as possible moderators. Child and adolescent characteristics were assessed using the Junior Temperament and Character Inventory, the Child Behaviour Checklist and the Youth Self Report. Early life stress was determined by a risk index measuring the presence of 11 adversity factors. Results did not reveal an association with 5-HTTLPR genotype. There were no moderating effects of early life stress or gender. An explanation for the negative findings is that the S allele may be a necessary but not sufficient component cause in a composite risk factor.

In recent years, studies focussing on a possible association between the dopamine D4 receptor (DRD4) gene exon III polymorphism and the personality trait of novelty seeking (NS) have yielded inconsistent results. The present study sought to examine the association of the DRD4-7r allele with NS in a sample of 303 15-year-old adolescents (144 males, 159 females) using data from a high-risk community sample. The Junior Temperament and Character Inventory--JTCI/12-18 was administered to assess dimensions of adolescent temperament. Males in the DRD4-7r allele group scored significantly higher on the NS (p=.002) and the harm avoidance (p=.045) scales than males without this allele. In females no association with temperament was observed. This association could not be explained by the presence of either an attention-deficit/hyperactivity disorder (ADHD) or a DRD4 by ADHD interaction.

Background: In recent years, a growing number of studies has focused on the dopamine D4 receptor gene (DRD4) as mediating the susceptibility to attention-deficit/hyperactivity disorder (ADHD). While their results are contradictory, the reason for this inconsistency remains as yet unclear., Method: The present study sought to examine the association between ADHD and the DRD4 exon III polymorphism during child development using longitudinal data from a high-risk community sample (n = 265, 129 females, 126 males) who have been followed from birth to 11 years of age., Results: Higher rates of ADHD were observed in boys with the 7 repeat allele of exon III than in boys with other alleles at the ages of 4 1/2 (Fisher's exact test, p = .061), 8 (p = .026), and 11 years (p = .005). Boys with this allele also exhibited higher rates of persistent disorder (p = .024). In girls, a trend towards an association (p = .055) with the 7 repeat allele emerged only at preschool age., Conclusions: These findings provide additional evidence for the role of the dopamine D4 receptor in ADHD during the course of child development.