Prenatal unhealthy diet, insulin‐like growth factor 2 gene ( IGF 2 ) methylation, and attention deficit hyperactivity disorder symptoms in youth with early‐onset conduct problems

Background Conduct problems ( CP ) and attention deficit hyperactivity disorder ( ADHD ) are often comorbid and have each been linked to ‘unhealthy diet’. Early‐life diet also associates with DNA methylation of the insulin‐like growth factor 2 gene ( IGF 2 ), involved in fetal and neural development. We investigated the degree to which prenatal high‐fat and ‐sugar diet might relate to ADHD symptoms via IGF 2 DNA methylation for early‐onset persistent ( EOP ) versus low CP youth. Methods Participants were 164 youth with EOP ( n  =   83) versus low ( n  =   81) CP drawn from the Avon Longitudinal Study of Parents and Children. We assessed if the interrelationships between high‐fat and ‐sugar diet (prenatal, postnatal), IGF 2 methylation (birth and age 7, collected from blood), and ADHD symptoms (age 7–13) differed for EOP versus low CP youth. Results Prenatal ‘unhealthy diet’ was positively associated with IGF 2 methylation at birth for both the EOP and low CP youth. For EOP only: (a) higher IGF 2 methylation predicted ADHD symptoms; and (b) prenatal ‘unhealthy diet’ was associated with higher ADHD symptoms indirectly via higher IGF 2 methylation. Conclusions Preventing ‘unhealthy diet’ in pregnancy might reduce the risk of ADHD symptoms in EOP youth via lower offspring IGF 2 methylation.