Early motor developmental milestones and level of neuroticism in young adulthood: a 23-year follow-up study of the Copenhagen Perinatal Cohort

Background. Studies investigating early developmental factors in relation to psychopathology have mainly focused on schizophrenia. The personality dimension of neuroticism seems to be a general risk factor for psychopathology, but evidence on associations between early developmental precursors and personality traits is almost non-existent. This study is therefore the first to investigate associations between early motor developmental milestones and neuroticism in adulthood. Method. Mothers of 9125 children of the Copenhagen Perinatal Cohort recorded 12 developmental milestones during the child's first year of life. A subsample of the cohort comprising 1182 individuals participated in a follow-up when they were aged 20-34 years and were administered the Eysenck Personality Questionnaire (EPQ). Associations between motor developmental milestones and level of neuroticism, extraversion and psychoticism were analysed by multiple linear regression adjusting for for sex, single-mother status, parity, mother's age, father's age, parental social status and birth weight. Results. Among the 1182 participants with information on the EPQ, information on milestones was available for 968 participants. Infants who developed high levels of neuroticism as adults tended to sit without support, crawl, and walk with and without support significantly later than individuals with low levels of neuroticism (p values <0.05). These results remained significant after adjustment for the included covariates and for adult intelligence. Conclusions. The findings are the first of their kind and suggest that delays in early motor development may not only characterize psychopathological disorders such as schizophrenia, but may also be associated with the personality dimension of neuroticism in adulthood.