Previous cross-sectional studies suggest that birth weight (BW) is associated with aggression-, social- and attention problems differently in boys and girls. We sought to test if these differences could be confirmed in a longitudinal study. The 1989 Raine Study provided prospectively collected data on perinatal variables and repeated child behaviour checklist assessments from ages 5 to 17. Linear mixed effects models provided crude and adjusted relationships between BW and childhood behaviour at a conservative significance threshold using prenatal maternal covariables in adjusted models. Sensitivity analyses included an age10 teacher assessment. Data on behaviour, BW and sex, was available in 2269 participants. Male sex was associated with increased aggression problems at lower BW compared to females in the crude model (Interaction B: -0.436, 98.3%CI: [-0.844, -0.0253]), but not the adjusted model (Interaction B: -0.310, 98.3%CI: [-0.742, 0.140]). Male sex was associated with increased attention problems at lower BW compared to females in both the crude model (Interaction B: -0.334, 98.3%CI: [-0.530, -0.137]) and the adjusted model (Interaction B: -0.274, 98.3%CI: [-0.507, -0.0432]). Male sex was associated with increased social problems at lower BW compared to females in both the crude model (Interaction B: -0.164, 98.3%CI: [-0.283, -0.0441]) and the adjusted model (Interaction B: -0.148, 98.3%CI: [-0.285, -0.00734]). Using repeated measures from ages 5–17 we were able to show a crude and adjusted male vulnerability to lower BW in the development of attention problems and social problems. We did not find a BW x sex interaction for the development of aggressive behaviour.
