RT Journal
A1 Rosenberg RE, Law J, Yenokyan G, McGready J, Kaufmann WE, Law PA
T1 CHaracteristics and concordance of autism spectrum disorders among 277 twin pairs
JF Archives of Pediatrics & Adolescent Medicine
JO Archives of Pediatrics & Adolescent Medicine
YR 2009
FD October 5
VO 163
IS 10
SP 907
OP 914
DO 10.1001/archpediatrics.2009.98
UL http://dx.doi.org/10.1001/archpediatrics.2009.98
AB Objectives 
    To examine patterns of autism spectrum disorder (ASD) inheritance and other features in twin pairs by zygosity, sex, and specific ASD diagnosis.Design 
    Cross-sectional study.Setting 
    Internet-based autism registry for US residents.Participants 
    Survey results from 277 twin pairs (210 dizygotic [DZ] and 67 monozygotic [MZ]) aged 18 years or younger with at least 1 affected twin.Main Exposures 
    Zygosity and sex.Outcome Measures 
    Concordance within twin pairs of diagnosis, natural history, and results from standardized autism screening.Results 
    Pairwise ASD concordance was 31% for DZ and 88% for MZ twins. Female and male MZ twins were 100% and 86% concordant, respectively, and DZ twin pairs with at least 1 female were less likely to be concordant (20%) than were male-male DZ twin pairs (40%). The hazard ratio for ASD diagnosis of the second twin after a first-twin diagnosis was 7.48 for MZ vs DZ twins (95% confidence interval, 3.8-14.7). Affected DZ individual twins had an earlier age at first parental concern and more frequent diagnoses of intellectual disability than did MZ twins; MZ twins had a higher prevalence of bipolar disorder and Asperger syndrome and higher concordance of the latter. Results of autism screening correlated with parent-reported ASD status in more than 90% of cases.Conclusions 
    Our data support greater ASD concordance in MZ vs DZ twins. Overall higher functioning, psychiatric comorbidity, and Asperger syndrome concordance among affected MZ vs DZ twins may also suggest differential heritability for different ASDs. For families in which one MZ twin is diagnosed with ASD, the second twin is unlikely to receive an ASD diagnosis after 12 months. In addition, Internet parent report of ASD status is valid.