5.1 Genetic and environmental influences
Until quite recently, the dominant view of attachment formation has been an environmental one, stressing the causal factors of sensitivity and other aspects of caregiving. However, while the evidence has stacked up for these environmental causes of differences in attachment relationships, the ‘strength of effect’ of these causes has consistently been shown to explain only part of the differences. For example, a meta-analysis of the effect size for maternal sensitivity has estimated that only about one-third of the variance in attachment security can be explained by variance in maternal sensitivity. Other factors such as emotionality and emotional responsiveness, and mind-mindedness, have additional effects, and a ‘cumulative risk’ model is now emerging for poorer attachment outcomes in which factors such as these and socio-economic factors have additive effects. But even with these additive effects, there is still variation among children’s attachment outcomes which cannot be explained by environmental variation. There is now an increasing interest in genetic differences in children and how these may also be significant influences on outcomes.
Disorganised attachment has been a particular focus of research in respect of the contributions that genetic variation and differences in caregiving environment make to the development of this outcome, which has negative consequences for children’s subsequent adolescent and adult life. While this is a relatively new and dynamic field of research, it has already shown the complexity of the mechanisms that underlie attachment disorganisation, and has provided some new insights into how genes and environments appear to interact in development.