Writing hand preference and child mental health in the general population: Findings from the Millennium Cohort Study

Non-right-handed individuals appear to face greater risks for some psychiatric disorders than those right-handed. Whether an analogous association exists in the general child population and for whom (non-right-handed, left-handed, or mixed-handed children) is unclear. To fill these gaps, we used data from 7,951 children (49.48% girls) of the UK's Millennium Cohort Study. The parent-reported Strengths and Difficulties Questionnaire (SDQ) subscales measured mental health difficulties: emotional, conduct, hyperactivity/inattention, peer difficulties, and prosocial behaviour, at ages 3, 5, 7, 11, and 14 years. Handedness (writing hand preference: right/left/either hand) was self-reported at 14 (a retrospective measure). Adjusted growth curve models explored the association between children's handedness and SDQ trajectories across 3-14. Non-right-handed (left-handed and mixed-handed) children exhibited elevated hyperactivity/inattention symptoms compared to those right-handed, with the association becoming nonsignificant after excluding the mixed-handed. Sex-stratified models did not show any association for girls. Among boys, the non-right-handed, compared to the right-handed, had higher hyperactivity/inattention and peer difficulties scores, though not after excluding the mixed-handed group. All effects were very small. Results suggest that left-handedness is not conferring risk for mental health in the general child population. Mixed-handed children, particularly boys, may face greater risks for social difficulties and hyperactivity/inattention, but effects were very small.