Association of ASD, traits and age variables with socio-demographic variables.

Gender effect is for females. Birth order coded as 0 (no older siblings) and 1 (one or more older siblings). Paternal social class coded as I, II, III non-manual, III manual and IV+V combined. Maternal educational qualifications coded as none or CSE, vocational, O level, A level or degree. Housing coded as mortgaged/owned, local authority housing and other. Traits are coded so that low scores reflect a more favourable response. Traits are labelled as in Table 3. Age variables are labelled as given in Table 4. Reported effect sizes relate to a linear trend. Effect sizes are ORs for ASD and regression coefficients for other outcomes. Standard errors (or exp(SE) for ASD) are given in parentheses.