When assessed in childhood, the mean age of the cohort was 6 years 9 months (SD 2 year 9 months; range 2–13 years); their mean age as adults was 44 years 2 months (SD 9 year 4 months; range 29– 64 years). The mean time between initial assessment and follow-up was 37 years 6 months (SD 9 year 2 months; range 23–59 years). Among the total group, 44 participants (37 males, 7 females) had also been previously assessed when aged 16 years or older (average age 26 year 1 month, SD 8 year 2 months, range 16–46 years) allowing for further analysis of change from childhood through later adolescence/early adulthood to mid/ later adulthood. In describing our findings, we report overall changes from childhood to adulthood in the total sample (Child-Adult cohort, N = 60). Data on the subgroup of 44 individuals who were additionally assessed in later adolescence/early adulthood are used to explore patterns of change in IQ over three time points [T1 (childhood) through T2 (late adolescence early adulthood) to T3 (mid/ later adulthood)].