Two authors (D.R. and R.U.) extracted data from eligible articles: study year, author, region of study origin, sex, mean age, and age range of high-risk group and controls, number of follow-ups, parental diagnoses, methods of diagnosis in parents and offspring, blinding of child assessors to parent diagnosis (as reported in primary publications; assumed lack of blindness if not reported), method of recruitment and control group type (unscreened vs. screened parents).