The Val66Met brain-derived neurotrophic factor gene variant interacts with early pain exposure to predict cortisol dysregulation in 7-year-old children born very preterm: Implications for cognition

•BDNF modulates the association between neonatal pain/stress & cortisol levels.•↑ pain/stress associated with ↓ hair, ↑ reactivity cortisol in boys with BDNF Met.•Salivary cortisol reactivity −ve correlated with IQ & visual-motor integration.•Met allele may increase vulnerability to neonatal pain/stress sex-dependently.