Frequency of truancy at high school: evidence for genetic and twin specific shared environmental influences.

PURPOSE The purpose of this study was to examine the relative influence of genetic and environmental factors on variation in truancy during high school. We examined the significance of genetic and shared and nonshared environmental influences. In addition, we tested for the presence of environmental factors specifically shared by twins, but not by their siblings. METHODS A threshold model was used to analyze data from 4,835 twins and their non-twin siblings. RESULTS Results showed a higher prevalence of truancy for males (38% vs. 29%) and an increase in prevalence with age (beta = -.53). Individual differences in frequency of truancy were partly explained by genetic influences (h(2) = 45%); for twins, the environmental variance was partitioned into 25% shared by twins, and 30% nonshared, whereas for singletons all environmental variance was nonshared (i.e., 55%). CONCLUSIONS Prevalence of truancy was higher for boys than for girls and it increased with age. Genetic and environmental influences accounted for the variance in frequency of truancy. Part of the shared environment represents influences that are shared by twins but not by non-twin siblings.