Distributions of the different variables in the study sample and in participants who were excluded because DNA was unavailable are shown in Table S1 (see Supplement 1). The proportions of smoking and unmarried mothers and of unskilled-worker families at birth/14 years were greater in non-participants. Females were more eager to participate than males. No differences were found for smoking at 14/31 years, novelty seeking, and socio-economic status at 31 years (Table S1 in Supplement 1).
