Original Research

Dyadic trauma and attachment: A monozygotic twin study assessing the efficacy of Somatic Experiencing®

Joseph P. Riordan
Journal of Applied Neurosciences | Vol 1, No 1 | a3 | DOI: https://doi.org/10.4102/jan.v1i1.3 | © 2022 Joseph P. Riordan | This work is licensed under CC Attribution 4.0
Submitted: 15 May 2022 | Published: 28 July 2022

About the author(s)

Joseph P. Riordan, Private capacity, Queensland, Australia


Orientation: Monozygotic twins offer a unique opportunity to examine the contagious nature of trauma in attachment dyads when one twin experiences trauma, but the other does not. Dyadic trauma is antagonistic to secure phylogenetic attachment (SPA).

Research purpose: Attachment perturbations in trauma may be complicit in psychopathology. Somatic Experiencing (SE) is an effective treatment for post-traumatic stress disorder (PTSD), and attachment focused somatic experiencing (AF-SE) resolves dyadic trauma.

Motivation for the study: Monozygotic twins may share a unique form of sibling attachment, described here as monozygotic attachment, characterised by elevated somatic congruence resulting in suboptimal attachment. The study was conducted to determine whether dyadic trauma is contagious and compromises SPA and whether SE and AF-SE are effective treatments to restore SPA.

Research approach/design and method: A quantitative experimental approach was used to examine the nature of trauma in monozygotic attachment and the significance of trauma in relation to psychopathology. Smartphone devices were used to record seven autonomic variables pre- and post-treatment for both twins: heart rate variability (HRV), three HRV index variables, heart rate, sleep duration and sleep disturbances. Mean and small sample t-tests were applied to determine statistical significance.

Main findings: Results conclude that trauma is contagious in attachment dyads and contributes to psychopathology. Somatic Experiencing is an effective treatment for trauma. The AF-SE resolves dyadic trauma restoring SPA as the antithesis of trauma.

Implications for practice: Traumatology and attachment theory may be linked theoretically to resolve trauma.

Contribution/value-add: Secure phylogenetic attachment offers a new category of attachment theory that defines trauma in dyads and its relationship to psychopathology.


dyadic trauma; dyadic completion; monozygotic; secure phylogenetic attachment; somatic experiencing


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Crossref Citations

1. Attachment Traumatology: Interpersonal neurosynchronistic phylogenesis
Joseph P. Riordan
Journal of Applied Neurosciences  vol: 2  issue: 1  year: 2023  
doi: 10.4102/jan.v2i1.7