1 Division of Health Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom.
2 Crown Princess Victoria Children's Hospital, Region Östergötland, Linköping, Sweden.
3 Division of Pediatrics, Dept of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden.
4 Department of Public Health, Erasmus MC-University Medical Center Rotterdam, Rotterdam, The Netherlands.
5 Centre de recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec, Canada.
6 École de santé publique, Université de Montréal, Montréal, Québec, Canada.
7 Murdoch Children's Research Institute and Department of Paediatrics, The University of Melbourne, Melbourne, Victoria, Australia.
8 PERFORM Centre, Concordia University, Montreal, Quebec, Canada.
9 Stanford University, Stanford, California, United States of America.
10 Department of Health, Medicine and Caring Science/Inst of Society and Health/Public Health, Linköping University, Linköping, Sweden.
11 Department of Child and Adolescent Psychiatry/Psychology, Erasmus MC-University Medical Center Rotterdam, Rotterdam, the Netherlands.
12 Department of Psychology, Education, and Child Studies, Erasmus MC-University Medical Center Rotterdam, Rotterdam, the Netherlands.
13 Cree Board of Health and Social Services of James Bay, Department of Program Development and Support, Chisasibi, Québec, Canada.

CONCLUSION: Findings indicate that children in families with high household income or maternal education are less likely to have ADHD at age 9-11. Absolute inequality, in combination with relative inequality, provides a more complete account of the socioeconomic status and ADHD relationship in different high-income countries. While the study design precludes causal inference, the linear relation between early childhood social circumstances and later ADHD suggests a potential role for policies...