PURPOSE:A growing body of evidence links poor maternal mental health with negative outcomes on early child development. We examined the effect of antenatal and postnatal maternal mental health on infant neurodevelopment at age 18 months in a population-based mother-child cohort (Rhea Study) in Crete, Greece. METHODS:Self-reported measures of maternal depression (EPDS), trait anxiety (STAI-Trait) and personality traits (EPQ-R) were assessed in a sample of women during pregnancy and at 8 weeks postpartum (n = 223). An additional sample of 247 mothers also completed the EPDS scale at 8 weeks postpartum (n = 470). Neurodevelopment at 18 months was assessed with the use of Bayley Scales of Infant and Toddler Development (3rd edition). RESULTS:Multivariable linear regression models adjusted for confounders revealed that antenatal depressive symptoms (EPDS ≥ 13) were associated with decrease in cognitive development independently of postnatal depression. High trait anxiety and extraversion were associated with decrease and increase, respectively, in social-emotional development. Also, high trait anxiety and neuroticism had a positive effect on infants' expressive communication. Finally, postpartum depressive symptoms (EPDS ≥ 13) were associated with decrease in cognitive and fine motor development independently of antenatal depression. CONCLUSIONS:These findings suggest that antenatal and postnatal maternal psychological well-being has important consequences on early child neurodevelopment.