Rationale: Internalising problems (depression & anxiety) in children have been found to be predictive of negative outcomes later in life (Sallis et al., 2018) but the biological mechanisms underlying the development of these disorders are not well understood. There is some evidence that epigenetics might play a role, but results are mixed (Barker, Walton, & Cecil, 2018). In this study, we will examine internalizing traits in childhood and methylation, both cross-sectionally and at birth.