Skip to main content
. Author manuscript; available in PMC: 2015 May 21.
Published in final edited form as: Arch Gen Psychiatry. 2011 Jul 4;68(11):1095–1102. doi: 10.1001/archgenpsychiatry.2011.76

Table 4.

Tests of Hypotheses, California Autism Twins Study, 1987–2004 Births

Hypothesis Tested Parameter
Constraint		 df Strict Autism (Narrow) ASD (Broad)
χ2 P Value χ2 P Value
Perfect correlation in liability between M and F rmf = 1 1 2.68 .10 4.62 .03
Equal heritability and equal twin environment for M and F Am = Af; Cm = Cf 2 0.81 .67 3.28 .19
Equal heritability and equal twin environment for M and F, perfectly correlated Am = Af; Cm = Cf; rmf = 1 3 2.98 .40 7.28 .06
No heritability Am = Af = 0 2 8.86 .01 18.55 <.001
No twin environment Cm = Cf = 0 2 7.64 .02 18.61 <.001

Abbreviations: Af, additive genetic variance for females; Am, additive genetic variance for males; ASD, autism spectrum disorder; Cf, shared twin environmental variance for females; Cm, twin environmental variance for males; F, females; M, males; rmf, male-female correlation in variance components.