Prenatal Risk Factors and the Etiology of ADHD—Review of Existing Evidence
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While it is well accepted that attention-deficit/hyperactivity disorder (ADHD) is a highly heritable disorder, not all of the risk is genetic. It is estimated that between 10 and 40% of the variance associated with ADHD is likely to be accounted for by environmental factors. There is considerable interest in the role that the prenatal environment might play in the development of ADHD with previous reviews concluding that despite demonstration of associations between prenatal risk factors (e.g. prematurity, maternal smoking during pregnancy) and ADHD, there remains insufficient evidence to support a definite causal relationship. This article provides an update of research investigating the relationship between prenatal risk factors and ADHD published over the past 3 years. Recently, several epidemiological and data linkage studies have made substantial contributions to our understanding of this relationship. In particular, these studies have started to account for some of the genetic and familial confounds that, when taken into account, throw several established findings into doubt. None of the proposed prenatal risk factors can be confirmed as causal for ADHD, and the stronger the study design, the less likely it is to support an association. We need a new benchmark for studies investigating the etiology of ADHD whereby there is an expectation not only that data will be collected prospectively but also that the design allows the broad range of genetic and familial factors to be accounted for.
KeywordsADHD Etiology Prenatal Environmental Pregnancy
The authors would like to acknowledge Alicia White and the staff of Bazian Ltd for their work on the systematic reviews that this article builds upon. Dr Sciberras is funded by an NHMRC Early Career Fellowships in Population Health (No. 1037159). The Murdoch Childrens Research Institute is supported by the Victorian Government’s Operational Infrastructure Support Program.
Compliance with Ethical Standards
Conflict of Interest
Emma Sciberras, Melissa Mulraney and Desiree Silva declare that they have no conflict of interest.
David Coghill reports grants and personal fees from Shire; personal fees from Eli Lilly, Novartis, Sandoz and Oxford University Press; and grants from Vifor Pharma, outside the submitted work.
Human and Animal Rights and Informed Consent
This article does not contain any studies with human or animal subjects performed by any of the authors.
Papers of particular interest, published recently, have been highlighted as: • Of importance •• Of major importance
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