Childhood Adversity Trajectories and IQ in a Cohort of Young Adult Danish Men

OBJECTIVE Childhood adversity may interfere with cognitive development through stress-related biological changes and disadvantaged social environments. However, larger studies capturing the accumulation of multiple adversities throughout childhood are needed. We investigated the relationship between childhood adversity trajectories from 0 to 15 years and intelligence quotient (IQ) in 368 165 young adult Danish men. METHODS The Danish Life Course cohort containing data on 12 childhood adversities was linked with the Danish Conscription Registry containing data on IQ at ages between 18 to 26. We used 5 previously established childhood adversity trajectory groups (ages 0 to 15) based on a group-based multi-trajectory model: Low adversity, early life material deprivation, persistent material deprivation, loss or threat of loss, and high adversity. The association was examined using multivariable regression models adjusting for parental country of origin, maternal age, birth order, size for gestational age, and maternal education. RESULTS Mean IQ was highest in the low adversity group (102, SD: 14) and lowest in the high adversity group (91, SD: 16). Compared with the low adversity group, the adjusted mean IQs (95% CI) differed by −1.1 (−1.3;−1.0) points for the early life material deprivation group, −3.1 (−3.2;−2.9) points for the persistent material deprivation group, −2.6 (−2.8;−2.4) points for the loss or threat of loss group, and −6.4 (−6.7;−6.0) points for the high adversity group. CONCLUSION Using large-scale, multidimensional life-course data, our study showed a consistent inverse association between childhood adversity and IQ in young adulthood, underscoring the need for pediatric care that extends beyond clinical treatment and addresses children’s social environments.