Birth Weight Could Help Identify Children at Higher Risk of Psychological Issues

Summary: A child’s weight at birth could determine their risk of being diagnosed with a mental health disorder later in life. Researchers found for every kilogram below average birth weight, the more likely a child was to experience mental health problems through childhood and adolescence.

Source: RCSI

New research from RCSI University of Medicine and Health Sciences has found that babies with larger birth weights tend to have fewer mental health and behavioural issues in childhood and adolescence.

These findings could help to identify and support children at greater risk of developing psychological problems.

The study, published in European Child & Adolescent Psychiatry, examined birth weights and subsequent mental health in thousands of children in Ireland.

Unlike many studies looking at birth weight, it used data that followed the same children repeatedly throughout their childhood and adolescence using the Growing Up in Ireland study, an ongoing government-funded study of children born between 1997 and 1998.

The analysis showed that each kilogram below the average birth weight (3.5kg, or 7lbs 11oz) was associated with more reported mental health problems throughout childhood and adolescence. The study also found that these birth-weight-linked problems tend to persist throughout childhood, from ages 9 to 17.

The type of problems most strongly linked with birth weight were inattention, impulsivity and hyperactivity, behaviours generally associated with Attention Deficit Hyperactivity Disorder (ADHD). Each kilogram drop below the average birth weight was linked with a 2% increase in risk of ADHD-like behaviours, however such behaviours were within the normal range.

That is, even among children with very low birth weights (1.5kg), the average number of ADHD symptoms would probably not meet the threshold for an ADHD diagnosis.

Lower birth weight was also linked with emotional and social problems, particularly in the late teens. These problems were found to be more severe and closer to clinical thresholds, for example for diagnosis of depression or anxiety.

Professor Mary Cannon, Professor of Psychiatric Epidemiology and Youth Mental Health at RSCI and Principal Investigator on the study, said: “We have known for many years that low birth weight and premature birth is linked with higher risk of mental illness in the child. What this study shows is that even small deviations from the typical birth weight might also be relevant.”

Niamh Dooley, PhD student and lead author of the study, said. “This relationship between birth weight and child mental health persists even after accounting for factors that could influence both birth weight and mental health, like gender, socioeconomic factors and parental history of mental illness.

This shows a mom and newborn
These findings could help to identify and support children at greater risk of developing psychological problems. Image is in the public domain

“The effect of birth weight on later mental health is likely small, but it might interact with other risks like genetics and childhood stress, and have implications for understanding the origins of mental health and ill-health.”

This study shows the importance of good perinatal care and suggests that improving the overall health of women during pregnancy to ensure optimal birth weight may help reduce the risk of offspring developing mental health problems.

Children of low birth weight may benefit from psychological assessments in childhood and early intervention for mental health symptoms if detected to help minimise the burden of mental illness later in adolescence and adulthood.

Further research by the group has just been published in Research on Child and Adolescent Psychopathology. It indicates that a significant percentage of the association between birth weight and ADHD symptoms in Irish children can be explained by maternal substance-use during pregnancy (smoking, alcohol-use, non-prescription drug-use).

Funding: This research was supported by a StAR International PhD Scholarship awarded to Niamh Dooley and funding from the Health Research Board and Irish Research Council. Open Access funding was provided by the IReL Consortium. Professor Cannon is funded by a European Research Council Consolidator Award.

About this neurodevelopment and mental health research news

Author: Rosie Duffy
Source: RCSI
Contact: Rosie Duffy – RCSI
Image: The image is in the public domain

Original Research: Open access.
The persistent effects of foetal growth on child and adolescent mental health: longitudinal evidence from a large population-based cohort” by Mary Cannon et al. European Journal of Child & Adolescent Psychiatry


The persistent effects of foetal growth on child and adolescent mental health: longitudinal evidence from a large population-based cohort

Low birth weight for one’s gestational age is associated with higher rates of child psychopathology, however, most studies assess psychopathology cross-sectionally.

The effect of such foetal growth restriction appears to be strongest for attention problems in childhood, although adult studies have found associations with a range of outcomes, from depression to psychosis.

We explore how associations between foetal growth and psychopathology change across age, and whether they vary by sex.

We used a large nationally representative cohort of children from Ireland (N ~ 8000). Parents completed the Strengths and Difficulties Questionnaire (SDQ) at 3 time points (age 9, 13 and 17). Outcomes included a total problems scale and subscales measuring attention/hyperactivity, peer, conduct and emotional problems.

Foetal growth had significant associations with all problem scales, even after controlling for sex, socioeconomic factors and parental mental health.

The magnitude of these effects was small but relatively stable across ages 9–17. In males, foetal growth had the strongest associations with attention/hyperactivity and peer problems, whereas females showed more widespread associations with all four subscales.

There was a trend for the association between foetal growth and emotional problems to increase with advancing age, approaching the borderline-abnormal threshold by age 17.

Reduced foetal growth predicted persistently higher scores on all measured aspects of child and adolescent psychopathology. Associations with child attention/hyperactivity may generalize to a wider array of adult psychopathologies via adolescent-onset emotional problems.

Future studies should explore potential age-dependent effects of foetal growth into the early 20s.

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  1. My 1st child was 7#14.5oz no issues born full term . My second child was born early at 32½ weeks at 4#10oz stayed in NICU for 16 days..only issue was not being able to finish the bottles before going to sleep so finally one nurse helped and took the time our child could come home ..and did at 4#.5oz … (lost weight due to calories burned during feedings) My second child was in middle school where the health teacher i formed the class that if you were born early then you were retarded(their choice of words not mine) to some degree… my child has not had any signs of any type not physical or neurogical..and is now 22yrs old just cometed 4yrs of college earning a BS in Neuroscience with a minor in Chemistry and a BA in Spanish and currently obtaining a Masters degree in Biomedical sciences and engineering doing research with a very well known DR in Cancer research. In the Fall of 2024 will be attending MD/PHD program.

  2. I totally agree with this
    Mother’s taking alcohol and smoking during pregnancy is the cause of Lee birth weight together with severe stress and lack of rest. Constantly exhausted mother from no rest

  3. There might be a mild correlation between birthweight and mental condition. Even this is still to be demonstrated: a prevalence of mental health probability of 2% per kilogram below the average of 3.5kg means you have only 3 kg to play with which means a maximální m of 6%. That is bearly gonna be meaningful. Can you author publish the study results an raw data or at least explain why they think this is significant results prractically after saying that the rate of mental health condition is anyway i the expected range of the entire population. Now a less than rigorous study that claim a correlation is bad enough, why would anyone go as far as infering a causal link?

  4. Have they studied the neurology reason of birth ,such as kicking during early delivery .Involuntary movement ( development ). Is it that certain neurological aspects have not formed ? Or is it linked to premature uterus in the female .Everything is connected .Interesting topic .

  5. This is definitely not accurate, my son had a higher birth weight of 8 pounds and he was diagnosed with autism my daughter who had a low birth weight of 6 pounds is perfectly normal with no mental issues.

  6. So glad that they think they know what they are talking about. Completely wrong in my family.

  7. Ok folks I think we are getting ridiculous now. My family has a history of mental health and heavy birthweights; I think the idea this is causal is stupid. Why is nobody looking at the larger social-political-environmental factors that impact mental health? Low birth weights are probably also signs of potentially lower access to pre-natal care, less food security, stress in the mother during pregnancy, etc. It feels like your ignoring the forest for the trees, then trying to stop wildfires by blaming it on individual tree types for being too flammable.

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