Infant body weight has limited effects on mood and behavior disorders

Resume: Despite common belief, a new study reveals that a child’s body weight has little impact on mood or behavior disorders.

Fountain: university of bristol

Child body mass index is unlikely to have much of an impact on children’s mood or behavioral disorders, according to a study led by the University of Bristol and published today in eLife.

The results suggest that some previous studies, which have shown a strong link between childhood obesity and mental health, may not have fully accounted for family genetics and environmental factors.

Obese children are more likely to be diagnosed with depression, anxiety, or attention deficit hyperactivity disorder (ADHD). But the nature of the relationship between obesity and these mental health conditions is unclear.

Obesity could contribute to mental health symptoms, or vice versa. Alternatively, a child’s environment could contribute to both obesity and mood and behavior disorders.

“We need to better understand the relationship between childhood obesity and mental health,” said lead author Dr. Amanda Hughes, a senior research associate in epidemiology at Bristol Medical School: Population Health Sciences (PHS). from the University of Bristol.

“This requires separating the contributions of the child’s and parent’s genetics and environmental factors that affect the whole family.”

Dr. Hughes and colleagues examined genetic and mental health data on 41,000 eight-year-old children and their parents from the Norwegian Mother-Father-Child Cohort Study and the Norwegian Medical Registry of Births.

They assessed the relationship between the children’s body mass index (BMI), a ratio of weight to height, and symptoms of depression, anxiety, and ADHD. To help separate the effects of children’s genetics from the influence of other factors that affect the whole family, they also took into account parental genetics and BMI.

The analysis found a minimal effect of a child’s own BMI on their anxiety symptoms. There was also conflicting evidence about whether a child’s BMI influenced their ADHD or depressive symptoms. This suggests that policies aimed at reducing childhood obesity are unlikely to have a large impact on the prevalence of these conditions.

This shows a girl eating watermelon.
The results suggest that some previous studies, which have shown a strong link between childhood obesity and mental health, may not have fully accounted for family genetics and environmental factors. The image is in the public domain.

“At least for this age group, the impact of a child’s own BMI seems small. For older children and adolescents, it might be more important,” said Neil Davies, a professor at University College London (UCL).

When they looked at the effect of parental BMI on children’s mental health, the team found little evidence that parental BMI affected children’s ADHD or anxiety symptoms. The data suggested that having a mother with a higher BMI might be linked to depressive symptoms in children, but there was little 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 appears to be limited. As a result, interventions to reduce parental BMI are unlikely to have widespread benefits for children’s mental health,” added Alexandra Havdahl, a research professor at the Norwegian Institute of Public Health.

“Our results suggest that interventions designed to reduce childhood obesity are unlikely to achieve large improvements in children’s mental health. On the other hand, policies that focus on the social and environmental factors related to increased body weight, and that directly target children’s poor mental health, may be more beneficial,” Hughes concluded.

About this research news on neurodevelopment, weight and behavior

Author: press office
Fountain: university of bristol
Contact: Press Office – University of Bristol
Picture: The image is in the public domain.

See also

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original research: Open access.
Body mass index and childhood symptoms of depression, anxiety, and attention deficit hyperactivity disorder: an intrafamilial Mendelian randomization study.” by Amanda M. Hughes et al. eLife


Abstract

Body mass index and childhood symptoms of depression, anxiety, and attention deficit hyperactivity disorder: an intrafamilial Mendelian randomization study.

Background:

A higher BMI in childhood is associated with emotional and behavioral problems, but these associations may not be causal. Results from previous genetic studies imply causal effects, but may reflect the influence of demographics and family background.

Methods:

This study used data from 40,949 8-year-old children and their parents from the Norwegian Mother-Father-Child Cohort Study (MoBa) and the Norwegian Medical Registry of Births (MBRN). We investigated the impact of BMI on symptoms of depression, anxiety, and attention deficit hyperactivity disorder (ADHD) at age 8 years. We apply Mendelian within-family randomization, which accounts for familial effects by controlling for parental genotype.

Results:

Mendelian within-family randomization estimates using genetic variants associated with adult BMI suggested that a child’s own BMI increased their depressive symptoms (by 5 kg/m2 increased BMI, beta = 0.26 SD, CI = -0.01, 0.52, p = 0.06) and ADHD symptoms (beta = 0.38 SD, CI = 0.09, 0.63, p = 0.009). These estimates also suggested that maternal BMI, or related factors, may independently affect a child’s depressive symptoms (per 5 kg/m2 maternal BMI increased, beta = 0.11 SD, CI: 0.02, 0.09, p = 0.01). However, Mendelian within-family randomization using genetic variants associated with retrospectively reported infant body size did not support an impact of BMI on these results. There was little evidence of any estimate that the parent’s BMI affected the child’s ADHD symptoms, or that the child’s or parent’s BMI affected the child’s anxiety symptoms.

Conclusions:

We found inconsistent evidence that a child’s BMI affected their ADHD and depressive symptoms, and little evidence that a child’s BMI affected their anxiety symptoms. There was limited evidence of an influence of parental BMI. Genetic studies in samples of unrelated individuals, or the use of genetic variants associated with adult BMI, may have overestimated the causal effects of a child’s own BMI.

Money:

This research was funded by the Health Foundation. It is part of the HARVEST collaboration, supported by the Norwegian Research Council. Individual co-author funding: The European Research Council, South East Norway Regional Health Authority, Norwegian Research Council, Helse Vest, Novo Nordisk Foundation, University of Bergen, South East Norway Regional Health Authority, Trond Mohn Foundation, Western Norway Regional Health Authority, Norwegian Diabetes Association, UK Medical Research Council. The Medical Research Council (MRC) and the University of Bristol support the MRC Integrative Epidemiology Unit.

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