A sibling adoption study of adult attachment: The influence of shared environment on attachment states of mind

Abstract

This study extends existing research investigating sibling concordance on attachment by examining concordance for adult attachment in a sample of 126 genetically unrelated sibling pairs. The Adult Attachment Interview (George, Kaplan, & Main, 1985;Main, Goldwyn, & Hesse, 2003) was used to assess states of mind with regard to attachment. The average age of the participants was 39 years old. The distribution of attachment classifications was independent of adoptive status. Attachment concordance rates were unassociated with gender concordance and sibling age difference. Concordance for autonomous/non-autonomous classifications was significant at 61% as was concordance for primary classifications at 53%. The concordance rate for not-unresolved/unresolved was non-significant at 67%. Our findings demonstrate similarity of working models of attachment between siblings independent of genetic relatedness between siblings and generations (i.e., parent and child). These findings extend previous research by further implicating shared environment as a major influence on sibling similarities on organized patterns of attachment in adulthood. The nonsignificant concordance for the unresolved classification suggests that unresolved loss or trauma may be less influenced by shared environment and more likely to be influenced by post-childhood experiences or genetic factors.

Concordance of Attachment Representations in Mother-/Father-Child Dyads and between Siblings

“…Van Ijzendoorn, Moran, Belsky, et al (2000) found around 60% concordance for siblings' attachment behaviour, and other studies obtained similar results with dizygotic twins (e.g. O'Connor & Croft, 2001) and even with adults adopted in infancy or childhood (Caspers, Yucuis, Troutman, Arndt, & Langbehn, 2007). This result excludes the genetic effects present with monozygotic twins but absent from adopted siblings, suggesting the influence of environment on the development of attachment.…”

An Attachment Perspective on Borderline Personality Disorder: Advances in Gene–Environment Considerations

“…Twin and adoption studies [21,22] using the AAI have robustly suggested that the AAI assesses the unique meaning the adult has given to his or her attachment history and further, that this meaning is likely to reflect the environment (shared and nonshared) within families. A rather different, more genetic-driven set of findings has been suggested by questionnaire or self-report measures of adult romantic attachment styles operationalized on the dimensions of avoidance or anxiety, in which the suggestion emerges that these attachment constructs overlap with the Big Five personality traits in ways that point to shared genetic influences [20].…”

“…In the case of the former self-report measure, yielding scores for avoidance and anxiety, recent evidence suggests that they are in part heritable [20]. In contrast, environmental-not genetic-effects are highlighted in sibling studies [21] and adoption studies [22] relying on the AAI. Furthermore, robust meta-analytic evidence from 10,000 respondents linking AAI responses to mental health outcomes [23•] underscores the value of the AAI as an indicator of psychotherapeutic treatment progress and outcome [3, 24•].…”

Use of the Adult Attachment Interview to measure process and change in psychotherapy

“…Validity evidence is strong for conceiving of AAI security/insecurity as being linked not to one's genetic makeup but to shared (and nonshared or relationship-specific) environmental influences (Caspers, Yucuis, Troutman, Arndt, & Langbehn, 2007;. Powerful associations across generations between AAI responses of parents and infant patterns of attachment have attracted much attention, from Main et al's (1985) report through and beyond the first metaanalytic report on 854 parentÁchild relationships studied (van IJzendoorn, 1995) showing a large effect size (Cohen's d01.06) for AAI security/ insecurity predicting infantÁparent security/insecurity.…”