A high-fat, high-sugar diet in pregnancy may lead to symptoms of ADHD for offspring with early-onset conduct problems.
Study co-author Dr. Edward Barker, of King's College London in the United Kingdom, and colleagues publish their findings in the Journal of Child Psychology and Psychiatry.
According to Mental Health America, conduct disorder is a "repetitive and persistent pattern of behavior in children and adolescents in which the rights of others or basic social rules are violated."
Behavior may be aggressive, such as threatening or harming other people or animals, or nonaggressive, such as causing deliberate damage to the property of others.
Children or teenagers with conduct disorder may also engage in deceitful behavior - such as lying and theft - and skipping school, staying out past curfew, and other rule violations are common.
Dr. Barker and colleagues note that conduct disorder often co-occurs alongside attention deficit hyperactivity disorder (ADHD), and research has suggested that such co-occurrence arises from a more serious heritable factor than either condition alone.
Previous studies have linked an unhealthy diet in early life with both conduct disorder and ADHD, which researchers speculate is caused by DNA methylation of the insulin-like growth factor 2 (IGF2) gene. DNA methylation is an epigenetic process by which methyl groups are added to DNA, altering gene function.
IGF2 is involved in fetal development, as well as the development of brain areas involved in ADHD. As such, Dr. Barker and colleagues hypothesized that an unhealthy diet during pregnancy might affect this gene in a way that puts offspring at risk for behavioral problems.
Higher IGF2 methylation at birth with unhealthy prenatal diet
To assess this possible association, the team analyzed data of 164 children and their mothers who were part of the Avon Longitudinal Study of Parents and Children - also known as the "Children of the 90s" project.
Of these children, 83 had early-onset conduct disorder, while 81 had low levels of conduct problems.
The researchers assessed mothers' diets during pregnancy, as well as blood samples from their children - taken at birth and the age of 7 years - in order to determine whether prenatal diet affects IGF2.
Among both groups of children, those whose mothers had a diet high in fat and sugar during pregnancy showed higher DNA methylation of IGF2 at birth, compared with children whose mothers had a healthy diet in pregnancy.
Importantly, higher IGF2 methylation at birth among children with early-onset conduct disorder was linked to more symptoms of ADHD between the ages of 7-13 years.
Dr. Barker says this study "highlights the critical importance of a healthy diet during pregnancy."
"These results suggest that promoting a healthy prenatal diet may ultimately lower ADHD symptoms and conduct problems in children. This is encouraging given that nutritional and epigenetic risk factors can be altered."
Dr. Edward Barker
The team now plans to investigate how specific nutrition groups affect neural development, in order to better pinpoint the best foods for expectant mothers to consume to lower their offspring's risk of ADHD.
"We already know that nutritional supplements for children can lead to lower ADHD and conduct problems, so it will be important for future research to examine the role of epigenetic changes in this process," adds Dr. Barker.