Does taking paracetamol during pregnancy result in ADHD?
Of the many articles and press around ADHD, there are all too often misleading interpretations of the science that has been presented. In this article, we aim to demystify the associations made between paracetamol and ADHD.
Quite often our current views and the way we interpret an article is determined by its headline. The problem with this is that when the headline is misleading, people remember something that may not be accurate. For example, in September 2019 The Daily Mail, a UK newspaper, ran the following headline: “Pregnant women who take paracetamol risk giving birth to a child with behavioural problems, study claims” . The original study, however, did not make this claim. Instead, the study said that paracetamol, taken in the period 18-32 weeks of pregnancy is associated with aspects of child attention and hyperactivity until 7 years of age .
It is important to mention is that an observed statistical association between one variable (e.g., taking paracetamol) and an individual trait (e.g., attention, hyperactivity) does not necessarily lead us to interpret this as a causal relationship, e.g. where one factor causes/leads to another. Causation, therefore, needs to be distinguished from mere association – the link between two variables. The word ‘risk’ in the former headline, however, does imply causation. Which is why it is important to look beyond media scaremongering and review original sources to fully understand methodology used and conclusions drawn.
The original study in this example, looked at data collected by Avon Longitudinal Study of Parents and Children (ALSPAC). This is a world-leading birth cohort study between April 1991 and December 1992. These women and their partners have been followed up intensively over two decades. Women in the study were sent a questionnaire – which included a question on paracetamol use. Possible responses included every day, most days, sometimes or not at all. Most of the mothers (99%) who had taken paracetamol reported taking it “sometimes”.
ALSPAC additionally collected information of the child’s neurocognitive and behavioural development, and based on previous literature (i.e., the relationship between paracetamol intake and individual traits), the study focused on information related to cognition and behaviour. However, potential associations with educational abilities, speech characteristics, motor development and psychiatric measures of depression or psychosis were not performed. Although this data is available, the authors did not use these traits.
The selected factors that might influence paracetamol intake were: factors of health (asthma, indigestion, back pain, migraine, and pre-pregnancy BMI), health in period 18-32 weeks (poor health, had a cold, had flu, had other infection, had a headache), lifestyle (healthy diet, processed diet, drank alcohol), and social conditions (domestic chemical score). Although the authors carefully selected these confounder variables, there are many other variables that could have influenced the outcome of the study, for example, history of parental conduct problems.
It is also important to consider that there are many reasons why someone could take paracetamol and it will be a very difficult task to uncover all the confounding factors. For example, taking paracetamol might be due low tolerance to pain, daily stress, or perhaps some of the mothers developed a seasonal affective disorder (“winter blues”) of which headaches are one of the main symptoms. In addition, it is important to note that the focus of this paper was to look at the association between pregnant mothers who had taken paracetamol and the child’s neurocognitive outcome. Which does not rule out abnormal neurocognitive development in the children of mothers who abstained from taking paracetamol during pregnancy.
In conclusion, it is a very difficult task to control for all possible covariates that might be influencing the association between paracetamol intake during pregnancy and the child’s behavioural and cognitive outcome. In fact, the study’s outcomes and conclusion could have been completely different, if other factors would have been included in the study.
 Hayward. E. (2019) Pregnant women who take paracetamol risk giving birth to a child with behavioural problems, study claims. Mail Online, published: 16 September 2019, Available at: https://www.dailymail.co.uk/news/article-7467099/Pregnant-women-paracetamol-risk-child-behavioral-problems.html
 Golding et al. (2019). Associations between paracetamol (acetaminophen) intake between 18 and 32 weeks gestation and neurocognitive outcomes in the child: A longitudinal cohort study. Paediatric and Perinatal Epidemiology, Available at: https://onlinelibrary.wiley.com/doi/full/10.1111/ppe.12582