The interaction between polygenic risk and environmental influences: a direct test of the 3P model of insomnia in adolescents

Background: Stress is a universal phenomenon and one of the most common precipitants of insomnia. However, not everyone develops insomnia after experiencing a stressful life-event. This study aims to test aspects of Spielman’s ‘3P model of insomnia’ (during adolescence) by exploring the extent to which: 1) insomnia symptoms are predicted by polygenic scores; 2) life-events predict insomnia symptoms; 3) the interaction between polygenic scores and life-events contribute to the prediction of insomnia symptoms; 4) gene-environment interaction effects remain after controlling for sex.

Methods: The sample comprised 4629 twins aged 16 from the Twin Early Development Study who reported on their insomnia symptoms and life-events. Polygenic scores (PGS) for insomnia were calculated. In order to test the main hypothesis of this study (a significant interaction between PGS and negative-life events), we fitted a series of mixed effect regressions.

Results: The best fit was provided by the model including sex, PGS for insomnia, negative life-events and their interactions (AIC=26158.7). Our results show that the association between insomnia symptoms and negative life-events is stronger for those with a higher genetic risk for insomnia.

Conclusions: This work sheds light on the complex relationship between genetic and environmental factors implicated for insomnia. This study has tested for the first time the interaction between genetic predisposition (PGS) for insomnia and environmental stressors (negative life-events) in adolescents. This work represents a direct test of components of Spielman’s 3P model for insomnia which is supported by our results.