Childhood obesity is unlikely to have a significant impact on children’s mood or behavioural disorders, according to a study led by the University of Bristol.
The findings suggest that previous studies, which have claimed a strong link between childhood obesity and behavioural disorder, may not have fully considered family genetics and environmental factors.
The study features contributions from the University of Bristol, University College London and the Norwegian Institute of Public Health. The full findings have been published in the journal eLife.
Debate over the origin of behavioural disorders
Obese children are more likely to be diagnosed with depression, anxiety, or attention-deficit hyperactivity disorder (ADHD). However, prior to the new research, the nature of the relationship between childhood obesity and behavioural disorders has not been clear.
Obesity may contribute to mental health symptoms and vice versa. However, some researchers believe child’s environment might contribute to obesity, mood and behavioural disorders.
“We need to better understand the relationship between childhood obesity and mental health,” said lead author Dr Amanda Hughes, senior research associate in epidemiology in the Bristol Medical School: Population Health Sciences (PHS) at the University of Bristol.
“This requires teasing apart the contributions of child and parent genetics and the environmental factors affecting the whole family,” she added.
Dr Hughes and her team analysed genetic and mental health data from 41,000 eight-year-old children and their parents from the Norwegian Mother, Father, and Child Cohort Study and Medical Birth Registry of Norway.
The researchers examined the relationship between children’s body mass index (BMI) and symptoms of depression, anxiety and ADHD. In order to differentiate the effects of the children’s genetics from the influence of other factors that affect the whole family, they accounted for parental genetics and BMI.
The researchers found little association between children’s own BMI and their symptoms of anxiety. The study also revealed conflicting evidence on whether a child’s BMI influenced their depressive or ADHD symptoms. These findings suggest that policies focused on reducing childhood obesity are unlikely to have a significant impact on the prevalence of these conditions.
“At least for this age group, the impact of a child’s own BMI appears small. For older children and adolescents, it could be more important,” said Neil Davies, Professor at University College London.
Mother’s BMI may affect children’s mental health
When the researchers examined the effect of the parents’ BMI on the children’s mental health, they found minimal evidence suggesting that the parents’ BMI could affect children’s ADHD or anxiety symptoms. Data suggested that having a mother with a higher BMI may be linked to depressive symptoms in children, but there was little solid evidence of any link between the child’s mental health and the father’s BMI.
“Overall, the influence of a parent’s BMI on a child’s mental health seems to be limited. As a result, interventions to reduce parents’ BMIs are unlikely to have widespread benefits to children’s mental health,” added Alexandra Havdahl, Research Professor at the Norwegian Institute of Public Health.
“Our results suggest that interventions designed to reduce child obesity are unlikely to make big improvements in child mental health. On the other hand, policies which target social and environmental factors linked to higher body weights, and which target poor child mental health directly, may be more beneficial,” Hughes concluded.
