The number of preterm born children, defined as birth before the completed 37th week of gestation, has increased globally, with currently around 10% of all children worldwide being born preterm. Improvement in the management of risk pregnancies and neonatal care procedures in the last four decades have increased survival rates of all preterm born neonates and particularly those born very preterm. However, preterm birth has been linked to many long-term sequels related to cognitive function and mental health which are associated with gestational age at birth. Negative consequences are more likely among those born very preterm (<32nd week gestation), compared to moderate preterm (32nd-33rd weeks gestation) and late preterm children (34th-36th weeks gestation) but the latter two groups have less frequently been studied. In this project we study positive and negative aspects of wellbeing in preterm children, adolescents, and young adults and the role of protective factors for wellbeing potentially leading to resilience. Positive wellbeing involves high self-esteem and mental wellbeing, while negative wellbeing is defined by emotional and behavioural problems. We are studying protective factors on the individual level (academic skills, personality factors) and micro-system factors (family climate, parental mental health, peer relations). To answer these questions we analyse simultaneously data from six cohort studies (ALSPAC, British Cohort Study, Bavarian Longitudinal Study, Basel Study of Preterm Children, Millennium Cohort Study, and National Child Development Study) from UK, Germany, and Switzerland. Comparisons between the cohorts allow investigating differences between countries and epochs with different neonatal care procedures.