A genetic decomposition of the association between parasomnias and dyssomnias in 8-year-old twins.

OBJECTIVE

To estimate genetic and environmental influences on parasomnias and dyssomnias and their association in 8-year-olds.

DESIGN

Parents of twins completed the Children's Sleep Habits Questionnaire.

SETTING

Families were primarily tested at the Institute of Psychiatry, London, England.

PARTICIPANTS

A total of 300 pairs of 8-year-old twins and their parents participated in the study.

MAIN OUTCOME MEASURES

Sleep difficulties in children.

RESULTS

Individual differences in parasomnias and dyssomnias were largely explained by genes (accounting for 50% and 71% of the variances, respectively). The rest of the variances were mainly due to nonshared environmental influences. A moderate association was found between parasomnias and dyssomnias (r = 0.42), which was mainly accounted for by genetic influences (87%). The genetic correlation between parasomnias and dyssomnias was moderate (r = 0.61). In contrast, the nonshared environmental correlation was small (r = 0.10).

CONCLUSIONS

The decomposition of the association between parasomnias and dyssomnias suggests that there may be different manifestations of shared underlying genetic risks for sleep problems partly dependent on nonshared environmental influence.