Table 1.

VARIABLE NAME	Summary statistics
BACKGROUND INFORMATION AND COVARIATES	Mean [SD] or %
Mean Age [years]	19.63 [1.84]
Mean IQ [assessed at age 15.5 years]	96.33 [12.42]
Ethnicity [% white]	98%
Maternal educational level [% O level or less, A-levels, degree]	44%, 32%, 24%
Breastfeeding [breastfed for > 6 months]	45%
Birth complications index [Any]	20%
PREVALENCE OF STRESSFUL LIFE EVENTS	Mean	SD
Prenatal events	2.57	2.14
At 8 months	3.42	2.39
At 21 months	4.02	2.68
At 33 months	4.49	2.7
At 47 months	3.95	2.71
Adolescence (12–16 years)	1.52	1.45

SD = Standard deviation.