A diet high in fat and sugar during pregnancy may be linked to attention deficit hyperactivity disorder in children with behavioural problems early in life, experts have found.
The research, led by scientists from King’s College London (KCL) and the University of Bristol, is believed to be the first to indicate that an unhealthy diet alters the baby’s DNA in a way that might lead to brain changes and later ADHD.
ADHD and conduct problems are the most common reasons for child mental health referral in the UK and tend to occur in tandem. More than 40 per cent of children with a diagnosis of behavioural problems also have a diagnosis of ADHD in the UK.
A high fat, high sugar diet in pregnancy had already been associated with behavioural problems and ADHD, but the study, published in the Journal of Child Psychology and Psychiatry on Thursday, attempts to look at the processes involved.
Studying participants from the Bristol-based “Children of the 90s” cohort, the experts compared 83 children with early-onset persistent conduct problems with 81 children who had low levels of conduct problems. They assessed how the mothers’ nutrition changed IGF2, a gene involved in foetal development and the development of the cerebellum and hippocampus, areas of the brain implicated in ADHD.
The results showed high fat and sugar diets of processed food and confectionery were associated with greater modification of IGF2 in both sets of children. Higher IGF2 methylation was also associated with higher ADHD symptoms between the ages of seven and 13, but only for children who showed an early onset of behavioural problems such as lying or fighting.
Co-author Dr Edward Barker, from the department of psychology at KCL, stressed that parents with children with ADHD should not blame themselves because diet was just one factor, albeit a potentially significant one.
“ADHD/conduct problems are very complex psychiatric problems, they are multi-determined,” he said. “Diet could be an important but it’s going to be important alongside a host of other risks. A sensible diet can improve symptoms but it’s not a single causal agent.”
He also said the results did not prove causation and needed to be replicated in larger studies, but added to a weight of evidence about the importance of diet for good mental health.
“Diet can affect a range of psychiatric problems,” he said. “There’s good evidence that diet can affect depression. Of course it affects obesity, but obesity is related to how we feel about ourselves and can be related to ADHD.”
Dr Max Davie, the mental health lead at the Royal College of Paediatrics and Child Health, said the hypothesis applied to a fairly small subset of children.
“It may be that the mothers with a worse diet are more impulsive by nature, and hence find it hard to resist unhealthy options, and this inherited tendency is, at least in part, responsible for the presence of ADHD symptoms in their children,” he said.
“At present, this is not a study that would change my clinical practice, but if intervention studies resulting from this work show nutritional support in pregnancy can have an effect then we should take any opportunity we can to help.”