The NFBC used the TPQ subset of the TCI version 9, with 107 binary items. The YFS used the full TCI version 9 with 240 Likert items. HBCS used the TPQ version 4 with 98 binary items. NFBC, YFS and HBCS questionnaires were examined and the subset of questions identical to those administered to the QIMR sample were identified and used in all analyses. Negatively keyed questionnaire items were reverse scored as necessary. Persons missing >25% of data for a scale were set to missing for that scale. Persons missing <25% of data had any missing values imputed by the mean of other persons' responses (in the same study) to that item. The Likert-like scale used in the YFS was converted to a 0–1 measure by mapping 1=0, 2=0.25, 3=0.5, 4=0.75, and 5=1.0. A sum score across all items in a scale was taken as the final measure. The HBCS sum scores were regressed on age and sex, and residuals taken as the phenotype. The NFBC sample was of a uniform age, and the sum score was regressed only on
