title: Mixed-handedness is linked to mental health problems in children and adolescents.
abstract: OBJECTIVE
  Problems with language and symptoms of attention-deficit/hyperactivity disorder (ADHD) in childhood and adolescence are often strongly linked to low scholastic performance. Early recognition of children who are at increased risk is necessary. Our objective was to determine whether mixed-handedness, which is associated with atypical cerebral laterality, is associated with language, scholastic, and ADHD symptoms in childhood and adolescence.
  
  
  METHODS
  Prospective data come from the Northern Finland Birth Cohort 1986, a longitudinal, population-based birth cohort with assessments when children were 7 to 8 and 16 years of age (N = 7871). Teacher, parent, and/or adolescent reports were used to assess language difficulties, scholastic performance, and mental health, including ADHD symptoms.
  
  
  RESULTS
  Mixed-handed children, relative to right-handed, had approximately a twofold increase in odds of having difficulties with language and scholastic performance at the age of 8 years. Eight years later, as 16-year-olds, adolescents had twofold increase in odds concerning difficulties in school with language and with ADHD symptoms. Mixed-handed children were more likely to have scores indicating probable psychiatric disturbance, including ADHD symptoms. As adolescents, mixed-handed children with previous behavioral problems were at considerably higher risk for scoring within the range of probable ADHD-inattention or ADHD-combined case. Mixed-handedness was associated with greater symptom severity in children and adolescents (P = .01) concerning psychiatric disturbance and ADHD inattention but not ADHD hyperactivity.
  
  
  CONCLUSIONS
  The results indicate that mixed-handed children have a greater likelihood of having language, scholastic, and mental health problems in childhood and that these persist into adolescence. Thus, these results suggest that mixed-handedness, particularly in the presence of difficulties, could aid in the recognition of children who are at risk for stable problems. Additional research is needed to understand the connections between neural substrates related to atypical cerebral asymmetry, mixed-handedness, and mental health problems including ADHD symptoms.
authors.affiliation: Uppsala University, Department of Psychology, Box 1225, SE 751 42 Uppsala, Sweden. alina.rodriguez@psyk.uu.se
authors.forename: Alina
authors.initials: A
authors.lastname: Rodriguez
authors.forename: Marika
authors.initials: M
authors.lastname: Kaakinen
authors.forename: Irma
authors.initials: I
authors.lastname: Moilanen
authors.forename: Anja
authors.initials: A
authors.lastname: Taanila
authors.forename: James J
authors.initials: JJ
authors.lastname: McGough
authors.forename: Sandra
authors.initials: S
authors.lastname: Loo
authors.forename: Marjo-Riitta
authors.initials: MR
authors.lastname: Järvelin
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000503:physiopathology; D002648:Child; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007805:Language Development Disorders / Q000503:physiopathology; D016015:Logistic Models; D008297:Male; D001523:Mental Disorders / Q000503:physiopathology*; D009048:Motor Skills / Q000502:physiology