1. Department of Neurology, Child & Adolescent Headache Program University of California San Francisco San Francisco CA USA
2. Department of Neurology Albert Einstein College of Medicine New York NY USA
3. Department of Pediatrics University of California San Francisco San Francisco CA USA
4. Department of Epidemiology & Biostatistics University of California San Francisco San Francisco CA USA
5. NIHR‐Wellcome Trust King's Clinical Research Facility King's College London London UK