Maternal obesity during pregnancy increases risk for ADHD Symptoms

By Nestor Lopez-Duran PhD

Maternal obesity during pregnancy is not one of the usual suspects of risk factors for ADHD. Yet, it seems that there is some preliminary evidence associating maternal obesity and ADHD. The latest study showing this link was published in the last issue of the Journal of Child Psychology and Psychiatrist by Alina Rodriguez from the Uppsala University in Sweden and Imperial College in London.

  1. In this new study the author first presented 4 issues that remain unresolved from previous research linking maternal obesity and ADHD
  2. Since obesity is associated with distress, is it possible that it is the distress during pregnancy that increases the risk for ADHD rather than the obesity?
  3. It is possible that maternal obesity and child ADHD are simply related to a common genetic factor. In such a case, it would be the genetic factor, and not the obesity that increases the risk for ADHD
  4. Maternal obesity is associated with small birth weight due to fetal growth restrictions, and some studies have linked small birth size to ADHD, possibly through its effects on emotional regulation. Thus, is small birth size the possible link between maternal obesity and ADHD?
  5. Maternal obesity is also associated with childhood obesity. Is it possible then than the increased risk for ADHD is due to childhood obesity?

To begin to tackle these issues, the author examined a cohort of women who were pregnant in Sweden from 1999 to 2000. The cohort for this analysis included 1,714 mother-child dyads who were evaluated when the child was 5 years of age. The Body Mass Index of the mothers was obtained during pregnancy and divided into 4 groups: underweight (15–19.99), normal weight (20–24.99),  overweight (25–29.99), and obese (+30). ADHD symptoms and emotionality  at age 5 were assessed via a questionnaires completed by both mothers and teachers. A number of covariates (or potentially explanatory factors) were also measured including maternal stress during pregnancy (divorce, financial problems, etc), socio-economic   status, smoking, the childs own weight, and depression.

The results:

  1. 37% of the mothers were classified as either overweight or obese (28% overweight and 10% obese)
  2. Obese mothers were significantly more depressed than the mothers in any of the other weight categories
  3. Children of obese mothers had significantly more symptoms of inattention but not hyperactivity when these symptoms were reported by the teachers. Specifically, maternal obesity was associated with a 2-fold increase in risk of teacher-rated inattention symptoms when compared to the children of normal-weight mothers. This association remained stable after controlling for the possible explanatory factors.
  4. Maternal Obesity was also associated with an increased risk for negative emotion regulation difficulties as indicated by a teacher-reported emotionality questionnaire.
  5. Maternal Obesity was not associated with any symptom when the symptoms were reported by the mother.

A couple of things were surprising. First, the results of the teacher-reported inattention problems were strong, which was of note given that no association was found between obesity and hyperactivity. This discrepancy between inattention and hyperactivity actually points towards a clear link between obesity and adhd (at least inattentive type). That is, since obesity was associated with inattention but not hyperactivity, it is unlikely that the original findings reflected simply an association between obesity and more general behavioral problems in childhood. Instead, the link seems to be specific to one aspect of ADHD. Second, the lack of association between obesity and maternal reported symptoms continues a pattern of findings I have previously discussed (see  for example this article on the effects of multiple daycare arrangements) that suggests that there are some limitations in the nature of maternal reports of the child behavior. In my experience working on several large scale family-based longitudinal studies, fathers and teachers reports of kids behaviors tend to agree with each other, but these reports do not always agree with the mothers. It seems that mothers often see, or report, different behavioral tendencies in their children when compared to what teachers see (or report).

In sum, the study provides additional evidence linking maternal obesity to inattention problems in early childhood. This study expands previous findings by also showing that such a link can not be fully explained by a number of potential factors, such as maternal stress, depression, and socio-economic status. However, please also note that this study did not actually assessed for the presence of ADHD. That is, these kids did not undergo the comprehensive evaluation needed for an accurate diagnosis of ADHD. Instead, the study assessed ADHD-related symptoms as reported by teachers and parents. It would be interesting to see if obesity is associated with true ADHD diagnoses in this population.

The reference: Rodriguez, A. (2009). Maternal pre-pregnancy obesity and risk for inattention and negative emotionality in children Journal of Child Psychology and Psychiatry DOI: 10.1111/j.1469-7610.2009.02133.x