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 nonexistent. This study is therefore the first to investigate associations between early motor developmental milestones and neuroticism in adulthood.

Mothers of 9125 children in the Copenhagen Perinatal Cohort recorded 10 developmental milestones during the child's first life. A sub-sample of the cohort comprising 1182 individuals participated in a follow-up when they were 20–34 years old 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, birthweight, and adult intelligence.

Among the 1182 participants, information on individual milestones was available for 447–1045 individuals. Infants who developed high levels of neuroticism as adults tended to crawl, stand with- And without support and walk with- And without support significantly later than individuals with a low level of neuroticism. the results remained significant after adjustment for included covariates. Neither extraversion nor psychoticism was associated with age of attainment of developmental milestones.

The findings are the first of its 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.