highly significantp = 3.6 × 10 −6
In contrast, aggregating the five previously published twin register-based studies, which comprised 492 twin pairs, revealed proband wise concordance rates of 19.5% for MZ twins and 2.3% for DZ twins, a highly significant difference (OR = 6.71, 95% CI = 2.21–20.35; p = 3.6 × 10 −6 , Fisher’s exact test).