Socioeconomic inequalities in infant temperament

Background A low socioeconomic status (SES) has consistently been associated with behavioural problems during childhood. The studies of SES and behaviour in infants used temperament as a behavioural measure. However, these studies in younger children yielded inconsistent findings. Furthermore, they generally did not examine explanatory mechanisms underlying the association between SES and temperament. We investigated the association between SES and temperament in infancy. Methods The study was embedded in the Generation R study, a population-based cohort in The Netherlands. Maternal and paternal education, family income, and maternal occupational status were used as indicators of SES. At the age of 6 months, 4,055 mothers filled out six scales of the Infant Behaviour Questionnaire-Revised. Results Lower SES was associated with more difficult infant temperament as measured by five of the six temperament dimensions (e.g. Fear: unadjusted zscore difference between lowest and highest education: 0.57 (95%CI: 0.43, 0.71)). Only the direction of the association between SES and Sadness was reversed. The effect of SES on Distress to Limitations, Recovery from Distress, and Duration of Orienting scores was largely explained by family stress and maternal psychological well-being. These covariates could not explain the higher levels of Activity and Fear nor the lower Sadness scores of infants from low SES groups. Conclusions SES inequalities in temperament were already present in six months old infants and could partially be explained by family stress and maternal psychological well-being. The results imply that socioeconomic inequalities in mental health in adults may have their origin early in life.