Concordance rates for T1D in monozygous twins with long-term follow-up is >50%, compared to 6%-10% in dizygous twins, which is similar to what is found in nontwin siblings.
One study of 57 monozygous and 49 dizygous twin pairs reared apart and 90 nontwin siblings showed that impulsivity as assessed by a personality questionnaire was significantly correlated in the monozygous twins but not in the others.