Fifth, a quarter of the eligible twins for this study did not participate. Might this have biased our findings? Using data collected at the second interview wave, a multiple logistic regression analysis showed participation in the third wave to be strongly predicted by educational status but not by age, zygosity, level of alcohol use or alcohol abuse/dependence, or by several DSM-IV adult antisocial symptoms. With respect to vulnerability to the alcohol and externalizing symptoms, this sample was likely to be broadly representative of the original twin cohort.
