We constructed socioeconomic deprivation at age 5 from a standardised composite of household income, parents’ highest education, and parents’ highest occupational grade.22 We defined deprivation as the lowest third of the distribution. We determined attempted or completed suicide by any of the child’s biological mother, father, grandparents, aunts, or uncles from reports by biological parents, according to a standardised and validated protocol.23 We calculated a modified Reed’s score, which takes into account the number of affected relatives given the size and demographic structure of the family,24 and we considered children whose score was at or above the 80th centile to have a strong positive family history of suicide. When the children were aged 10 and 12, we interviewed mothers about the presence of attention/hyperactivity and conduct problems by using items drawn from the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV).25 We considered attention-deficit/hyperactivity disorder to be present if the child met DSM-IV criteria for this disorder at either 10 or 12 years of age; similarly, we deemed children to have conduct disorder if they met the relevant
