title: Prospective cohort analysis of cellphone use and emotional and behavioural difficulties in children.
abstract: BACKGROUND
  We previously reported associations between cellphone exposure and emotional and behavioural difficulties in children in the Danish National Birth Cohort using cross-sectional data. To overcome the limitations of cross-sectional analysis, we re-examined these associations with prospectively collected data.
  
  
  METHODS
  Based on maternal reports, prenatal and postnatal cellphone exposures were assessed at age 7 years, and emotional and behavioural difficulties were assessed at 7 and 11 years with the Strengths and Difficulties Questionnaire. We used multivariable-adjusted logistic regression models to estimate ORs and 95% CIs relating prenatal exposure and age-7 cellphone use to emotional and behavioural difficulties at age 11 years.
  
  
  RESULTS
  Children without emotional and behavioural difficulties at age 7 years, but who had cellphone exposures, had increased odds of emotional and behavioural difficulties at age 11 years, with an OR of 1.58 (95% CI 1.34 to 1.86) for children with both prenatal and age-7 cellphone exposures, 1.41 (95% CI 1.20 to 1.66) for prenatal exposure only, and 1.36 (95% CI 1.14 to 1.63) for age-7 use only. These results did not materially change when early adopters were excluded, or when children with emotional and behavioural difficulties at age 7 years were included in the analysis.
  
  
  CONCLUSIONS
  Our findings are consistent with patterns seen in earlier studies, and suggest that both prenatal and postnatal exposures may be associated with increased risks of emotional and behavioural difficulties in children.
authors.affiliation: Department of Epidemiology, Fielding School of Public Health, University of California, Los Angeles (UCLA), Los Angeles, California, USA.
authors.forename: Madhuri
authors.initials: M
authors.lastname: Sudan
authors.affiliation: Department of Public Health, Danish Epidemiology Science Centre, Aarhus University, Aarhus C, Denmark.
authors.forename: Jorn
authors.initials: J
authors.lastname: Olsen
authors.affiliation: Department of Epidemiology, Fielding School of Public Health, University of California, Los Angeles (UCLA), Los Angeles, California, USA.
authors.forename: Oyebuchi A
authors.identifier: http://orcid.org/0000-0002-9067-1697
authors.initials: OA
authors.lastname: Arah
authors.affiliation: Institute of General Medical Practice, Center for Collaborative Health, Aarhus University, Aarhus C, Denmark.
authors.forename: Carsten
authors.initials: C
authors.lastname: Obel
authors.affiliation: Department of Epidemiology, Fielding School of Public Health, University of California, Los Angeles (UCLA), Los Angeles, California, USA.
authors.forename: Leeka
authors.initials: L
authors.lastname: Kheifets
keywords: CHILD HEALTH; COGNITION; Cohort studies; EPIDEMIOLOGY