Assessments have been administered frequently, with 68 data collection time points between birth and 18 years of age (Supplementary Table S1, available as Supplementary data at IJE online). These include 34 child-completed questionnaires (CCQs, 25 including multiple domains and 9 focusing on pubertal development), 9 ‘focus’ clinical assessments and 25 questionnaires about the child completed by the mother or other main caregiver (MCQs). To aid the clarity of our reporting, we have retrospectively allocated each data collection into six phases (Supplementary Table S1a–f, available as Supplementary data at IJE online); ‘infancy’ (≥4 weeks and ≤2 years of age), ‘early childhood’ (>2 years and <7 years), ‘childhood’ (7 years of age), ‘late childhood’ (>7 years and <13 years), ‘adolescence’ (≥13 years and <16 years) and ‘transition to adulthood’ (>16 years and ≤18 years). The ‘infancy’ phase included four MCQs and a subsample, selected from the past 6 months of ALSPAC births, who were invited to the first four ‘Children in Focus’ (CiF) study assessment clinics. ‘Early childhood’ included 11 MCQs, 6 CCQs and the CiF subsample who were invited to a
