2008 Volume 74 Issue 3 Pages 130-145
The purpose of this study was to clarify genetic contributions to the childhood behavioral phenomena of sleeptalking, half-sleeping, night terrors, and nocturnal enuresis using the two largest databases of Japanese twins. The subjects were children of members of several maternal associations for multiples, including 765 pairs ranged in age from 3 to 15 years with a mean age of 7.0 years, as well as school applicants, including 1,140 twin pairs 11-12 years of age. All data were gathered by questionnaire. Structural equation modeling showed that the proportion of total phenotypic variance attributable to genetic influences was 88-96% regarding sleeptalking, 62-91% regarding half-sleeping, and 70-91% regarding night terrors, which were higher in the school applicants group than in the maternal associations group. Age and gender difference was suggested to impact nocturnal enuresis. Moreover, co-occurrence of sleeptalking, half-sleeping, and night terrors were attributed partly to common genetic or environmental factors for these three traits.