Attachment and temperament revisited: infant distress, attachment disorganisation and the serotonin transporter polymorphism

Abstract

Objective: This study’s aim was to evaluate whether infant disorganised attachment and infant proneness to distress exhibited differential relations to infant genetic factors as indexed by the serotonin transporter polymorphism. Background: The role of the short allele of the serotonin transporter polymorphism (5-HTTLPR) in enhancing sensitivity to fearful and negative affect has been well-established. In the current study, we used this known property of the short allele to provide a test of an important postulate of attachment theory, namely that infant attachment security or disorganisation is not a function of the infant’s proneness to distress. Methods: Participants were 39 parents and infants assessed between 12 and 18 months in the Strange Situation Procedure. Genotype categories for the 5-HTTLPR (and rs25531) were created by both the original and the reclassified grouping system; infant proneness to distress was assessed directly in the Strange Situation Procedure. We also assessed maternal behaviour at 18 months to evaluate whether any observed genetic effect indicated a passive effect through the mother. Results: Consistent with previous findings, the 5-HTTLPR short allele was significantly related to the infant’s wariness and distress, but was not related to attachment security or attachment disorganisation. In addition, maternal disrupted interaction with the infant was not related to infant genotype or infant distress. Conclusion: Results support the concept that infant proneness to distress is associated with serotonergic factors while infant attachment security or disorganisation is not a function of either 5-HTTLPR or behaviourally rated proneness to distress.

Key words:

• Serotonin transporter
• 5-HTTLPR
• infant distress
• infant attachment
• infant disorganisation

Acknowledgements

We would like to thank our most important collaborators, the families who have so generously given their time to this study.

Notes

1. The results did not reach significance when only crying was used as an index of distress. However, 11% of the variance in 12-months crying was accounted for by the number of 5-HTTLPR short alleles, consistent with results from the broader construct used here. The number of 5-HTTLPR short alleles predicted only 2% of the variance in 18-months crying, however, suggesting that explicit crying to separation is less strongly tied to this biological substrate with increasing age.

Additional information

Funding

This research was supported by NIMH Grant R01 MH062030 to Dr Lyons-Ruth.