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Gene-environment interactions

reported by Catherine H. Myers, Executive Director
Many researchers have contributed to the body of knowledge showing that early intimate relationships have significant and long-lasting effects on a child's emotional, social, cognitive and physical development. Recent studies on gene-environment interactions have examined children's genotypes and measurements of their mothers' mental health status or parenting behavior. These studies are providing new insights about the complex associations among infant attachment, temperament, mothers' mental health and parenting behaviors.

Marinus H. Van IJzendoorn and Marian J. Bakermans-Kranenburg of Leiden University, The Netherlands, set out to examine whether there was an association between infant attachment disorganization and the interaction of two factors: a gene variant-DRD4-that codes for a type of dopamine receptor, and mothers' mental health status. Two aspects of mothers' mental health were considered: loss/trauma and Frightening behavior. (Van IJzendoorn & Bakermans-Kranenburg, 2007).

Van IJzendoorn and Bakermans-Kranenburg ruled out many factors as correlates of infant attachment disorganization, including number of siblings, gender, and number of hours mothers worked (though only mothers working fewer than 33 hours per week were included in the study). The infants of older mothers scored higher on measures of disorganization. Frightening parenting was not found to correlate to infant disorganization, even when it occurred with long DRD4. There was no significant difference on attachment disorganization between infants with short DRD4 whose mothers had unresolved loss/trauma and those whose mothers did not have unresolved loss/trauma issues. However, there was a strong correlation with attachment disorganization for infants with both the long DRD4 gene and a mother with unresolved loss/trauma issues. (Van IJzendoorn & Bakermans-Kranenburg, 2007)

In discussing the results of their study, the authors pointed out that children with both the long DRD4 and a mother who had unresolved loss/trauma issues were classified in the disorganized attachment category 18 times as often as children without those two risk factors. (Van IJzendoorn & Bakermans-Kranenburg, 2007)

Psychology researchers at the University of Oregon have also taken a look at the long DRD4 gene in relation to parenting. Led by Brad E. Sheese, this research team is engaged in a longitudinal study of attention and temperament; they have been studying a group of child/parent pairs since the children were 7-9 months old. The researchers' objectives in this study were first to examine two variants of the DRD4 gene in relation to two aspects of temperament assessed when the children were 18-21 months: sensation seeking and effortful control (which is related to executive function). Second, the researchers examined whether there was a relationship between either of the DRD4 alleles and parenting quality that could predict either of the temperament measures. (Sheese, et al., 2007)

The researchers found that for those children without the 7-repeat allele, parenting quality had no significant effect. But parenting quality was found as a significant main effect on children's sensation seeking temperament for those children with the 7-repeat (long DRD4). Children with the 7-repeat allele who had high-quality parenting scored even lower than those without the 7-repeat allele on sensation seeking. And children with both the 7-repeat allele and low-quality parenting scored high on sensation seeking. (Sheese, et al., 2007)

Sheese et al. (2007) note that their evidence of this gene-environment interaction, which makes children more sensitive to parenting quality, may be an evolutionary advantage. If parents can more readily influence children's behavior one beneficial result might be more flexible and adaptive cultures. Low quality parenting was associated with higher ratings for children on the sensation seeking scale, and the researchers note this may be related to other research showing high incidence of the 7 repeat allele among children diagnosed with ADHD (attention deficit hyperactivity disorder). (Sheese et al., 2007)

Several cautions and possible opportunities were mentioned by the researchers. The parents in the study are volunteers, not a representational sample of the general parenting population. And, the researchers add that there might be genetic factors influencing parenting quality. In spite of these cautions, the researchers note the importance of continuing research to examine how parenting practices interact with children's genotypes, and the importance of measurements at various ages of the children as they plan to do with this cohort of parent/child pairs. Noting their study's confirmation of the importance of behavior interventions in childhood, the researchers suggest parent training might be a possibly effective intervention approach. (Sheese et al., 2007)

Both of the research studies described above demonstrate the importance and the complexity of the study of gene-environment interaction. Both studies showed that approximately one-fourth of children have a genetic variation that makes them especially sensitive to their parents' behavior, and that the effect on their development can be significant. (Van IJzendoorn & Bakermans-Kranenburg, 2007; Sheese et al., 2007)

There is much to be learned about gene-environment interaction as it relates to parenting. Scientists are doing more investigation of the specific parenting behaviors that affect children's development. Researchers are looking at whether parents' genes are a factor in their parenting behavior, and at which kinds of interventions might help parents create more positive outcomes for their children. (Van IJzendoorn & Bakermans-Kranenburg, 2007; Sheese, et al., 2007)

References

Sheese, B. E., Voelker, P. M., Rothbart, M. K. & Posner, M. I. (2007). Parenting quality interacts with genetic variation in dopamine receptor D4 to influence temperament in early childhood. Development and Psychopathology, 19. 1039-1046.

Van IJzendoorn. M. H. & Bakermans-Kranenburg, M. J. (2006). DRD4 7-repeat polymorphism moderates the association between maternal unresolved loss or trauma and infant disorganization. Attachment and Human Development, 8, 291-307.