The epidemiology of the mental and physical health of children and adolescents the world over reflects: the genomes they inherit (and the modifications those genes undergo in utero); the pregnancies that led to their births, whether their mothers survive those pregnancies, and whether their births were welcome; the parents, the neighbors, and the neighborhoods they "inherit" along with their genomes; when and where they live (by cohort, by country, and by province); the air they breathe; the water they drink; what and how much they eat; the schools they attend (and by whom they are taught what and for how long); the energy they expend; the family status in the social order; the friends they have; and last but not least, the amount and kind of medical and psychiatric care they receive.