Nature Human Behavior
Measuring childhood risk factorsWe measured risk factors that are thought to augur poor adult outcomes. All risk factor measures have been described in previous reports about this cohort.
Childhood socioeconomic status43 was defined as the average of the highest occupational status of either parent across study assessments from the cohort member’s birth through 11 years (1 = unskilled labourer; 6 = professional), on New Zealand’s occupational rating of the 1970s.
Childhood maltreatment44 includes evidence of: (1) maternal rejection assessed at 3 years of age by observational ratings of mothers’ interaction with the study children, (2) harsh discipline assessed at ages 7 and 9 years by parental report of disciplinary behaviours, (3) two or more changes in the child’s primary caregiver, and (4) physical abuse and (5) sexual abuse reported by study members once they reached adulthood. For each child, our cumulative index counts the number of maltreatment indicators during the first decade of life; 63.7% of children experienced no maltreatment, 26.7% experienced one indicator of maltreatment (hereinafter ‘probable’ maltreatment), and 9.6% experienced two or more indicators of maltreatment (‘definite’ maltreatment).
Childhood intelligence9 was measured as IQ with the Wechsler Intelligence Scale for Children – Revised (WISC-R) administered at ages 7, 9 and 11 years. IQ scores for the three ages were averaged and standardized.
Childhood self-control9 during the first decade of life was measured using nine measures of self-control: observational ratings of children’s lack of control (ages 3 and 5 years) and parent, teacher and self-reports of hyperactivity, lack of persistence, inattention, impulsive aggression and impulsivity (ages 5, 7, 9 and 11 years). The nine measures were positively and significantly correlated. Based on principal components analysis, the standardized measures were averaged into a single composite comprising multiple ages and informants, with strong internal reliability α = 0.86.
Caspi, A. et al. Childhood forecasting of a small segment of the population with large economic burden. Nat. Hum. Behav. 1, 0005 (2016).