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1 Smoking during pregnancy and child mental health and wellbeing Evidence, policy and practice Laura Vanderbloemen PhD University of York Department of Health Sciences 27 September 2013 3 Maternal smoking during pregnancy and child mental health and wellbeing: evidence, policy and practice Abstract Aim: The aim of this thesis was to further understand the link between maternal smoking during pregnancy and mental health outcomes among children. The thesis comprises (a) a longitudinal epidemiological analysis of smoking during pregnancy and child mental health outcomes using cohort data for UK children from before birth to 7 years of age (b) an exploration of what policy documents, official guidance and qualitative studies tell us about how the epidemiological risks of smoking in pregnancy are reflected in public policy and discourse. Methods: Existing epidemiological evidence was reviewed prior to the quantitative analyses. The data analysed are from the Millennium Cohort Study. Data for 13,161 mothers and children, analysed longitudinally, were used to link exposure to maternal smoking during pregnancy to child mental health outcomes (hyperactivity and aggressive behaviour) at 3, 5 and 7 years of age. Additionally a review of official and lay health guidance in two countries (United Kingdom and United States) was conducted to ascertain the extent to which the potential link between maternal smoking during pregnancy and increased risk of child mental health problems is reflected in ante-natal care policy and practice in these countries. Similarly, a review of qualitative studies was conducted to ascertain the extent to which the risk of child mental health problems is reflected in women's perceptions of the risks of smoking during pregnancy. Results: During the past 10 years high-quality studies (and studies of lower quality) have consistently observed an association between prenatal smoking exposure and child mental health problems, though a few well designed recent studies have provided conflicting findings, and further disentangling of exposure and potential confounding factors is needed. Prenatal smoking, socioeconomic position, genetics, family environment, parental mental health and other chemical and environmental exposures, including other endocrine disrupting chemicals, should be explored together, and in more depth, to understand the associations that have been observed between maternal smoking during pregnancy and child mental health during the past 20 years. The original and significant contribution of this thesis is a confirmation of the link between smoking in pregnancy and the development of disruptive behaviour problems in children in a large population-based sample from the United Kingdom. In terms of policy and discourse, ante-natal care packets could be modified to include information about these risks for pregnant women. Conclusions: Child mental health, prenatal smoking and the economic well- being of families are interlinked–so policies aimed at helping pregnant women to quit smoking, as well as those to help them out of disadvantage are likely to have positive effects on both the exposure (prenatal smoking) and the outcome (child mental health). 4 Maternal smoking during pregnancy and child mental health and wellbeing: evidence, policy and practice TABLE OF CONTENTS Abstract!! ! ! ! ! ! !! ! 3 List of Tables and Figures !! ! ! ! ! ! ! 7 Acknowledgements!! ! ! ! ! ! ! ! 8 Author’s Declaration!! ! ! ! ! ! ! ! 9 Thesis Aims!! ! ! ! ! ! ! ! ! 10 Outline !! ! ! ! ! ! ! ! ! ! 11 1! 12 Prenatal exposures and child health! 12 1.1 Exposure definitions: who smokes during pregnancy?! 13 Age-specific trends in smoking during pregnancy (UK) ..................................14 Trends in the U.S. (2008) ...................................................................................18 1.2 Outcome definitions: epidemiology of child hyperactivity and aggression! 19 Classification of child mental health problems ..................................................19 1.3 Cause and effect in intergenerational health: methodological challenges! 20 Methodological challenges and alternative explanations .................................23 Maternal smoking during pregnancy in the context of inequality .....................24 Establishing biological plausibility ....................................................................26 1.4 Chapter conclusions! 29 2! 31 Methods! 31 2.1 Review of existing evidence! 32 2.2 Quantitative analyses! 32 2.3 Review of policy, guidance and public discourse! 32 3! 33 A review of epidemiological studies of prenatal smoking exposure and child mental health problems, 2001-2013! 33 3.1 From biological (theoretical) plausibility to evidence! 34 Types of evidence needed to make a causal claim ..........................................36 3.2 Search Methodology ! 37 Title and abstract screening and evidence inclusion process .........................37 5 3.2 Findings from 2000-2010: prenatal smoking exposure and child mental health! 39 Longitudinal analyses .......................................................................................47 3.4 Update of studies, 2010-2013! 50 3.5 Chapter conclusions! 51 4! 55 Prenatal smoking exposure and child well-being in the Millennium Cohort, United Kingdom, 2000-2008! 55 4.1 Study design and methods! 60 Sequence of studies .........................................................................................60 Study population ...............................................................................................60 Sample size and follow up ................................................................................62 Exposure measurement variable .......................................................................64 Outcome variables ............................................................................................64 4.2 Results! 70 4.3 Multivariate logistic regression analyses, hyperactivity and aggressive behaviour in seven year olds! 72 4.4 Longitudinal analyses of prenatal smoking exposure and child mental health problems, Millennium Cohort Study, United Kingdom 2000-2008! 77 4.5 Chapter conclusions! 81 Main findings: not irreversible, not likely to be reversed ...................................81 5! 85 Review of policy, guidance and discourse in the United Kingdom and United States! 85 5.1 United Kingdom: What is the official (NICE) Guidance about maternal smoking during pregnancy?! 93 1. NICE Guidance: Antenatal and postnatal mental health: draft scope for consultation, 10 October–7 November 2012. ...................................................94 2. NICE Guidance: Antenatal care: routine care for the healthy pregnant woman, Clinical Guidance 62, 2010. ..............................................................................94 5.2 USA: What does the US Surgeon General’s Report advise about maternal smoking during pregnancy?! 97 5.3 Leading guidance accessed by pregnant women: United Kingdom! 99 5.4 Leading guidance accessed by pregnant women: United States! 105 6 Maternal smoking during pregnancy and child mental health and wellbeing: evidence, policy and practice 5.5 Discussion! 109 6! 115 Perception of risk: smoking during pregnancy and effects on children! 115 6.1 Critical perspectives on how risk is perceived! 117 6.2 Nested study from a systematic review of qualitative studies, 2012! 119 6.3 1976-1997: Early confusion about risk! 124 6.4 1998: The year of the Master Settlement Agreement! 127 6.5 1999-2006: Risk becomes prominent! 129 6.6 2005-2012: Bird nests and backlashes! 131 6.7 Chapter conclusions! 135 7! 136 Discussion and conclusions! 136 Explanatory Models: Health and well-being of children whose mothers smoke during pregnancy and how evidence is reflected in to policy, official guidance and public discourse ......................................................................................140 7.2 Evaluation and weak spots in the research base! 142 7.3 Implications for policy ! 143 Appendices! 144 References! 169 7 List of Tables and Figures Table 1.1 Common scales for child mental health assessment Table 3.1 Review of studies: Smoking during pregnancy and child mental health Table 4.1 Comparison of Baseline and Seven Year Follow up Socio-Demographic Characteristics, Millennium Cohort Study, United Kingdom, 2000-2008 Table 4.2 Distribution of Exposure, Outcome and Key Co-variates, Millennium Cohort Study at Baseline, United Kingdom, 2000-2001 Table 4.3 Adjusted odds of hyperactivity, 7 year olds, Millennium Cohort Study, United Kingdom, 2007-2008 (N=13,161) Table 4.4 Crude odds of conduct problems, 7 year olds, Millennium Cohort Study, United Kingdom, 2007-2008 (N=13,161) Table 4.5 Adjusted odds of conduct problems, 7 year olds, Millennium Cohort Study, United Kingdom, 2007-2008 (N=13,161) Table 4.6 Sensitivity analysis: Crude odds of hyperactivity and conduct problems, 7 year olds, Millennium Cohort Study, United Kingdom, 2007-2008 (N=5410) Table 4.7 Longitudinal trajectories of conduct problems, 3, 5 and 7 year olds, Millennium Cohort Study, United Kingdom, 2007-2008 Table 5.1 Summary of documents analysed for content relating to guidance for pregnant women who smoke in the United Kingdom and the United States Table 6.1 Results of nested review: papers that mention of risks of smoking during pregnancy Table 7.1 Summary of Findings from this thesis Box 1.1 Explanatory models of health inequalities (Bartley, 2004) Box 4.1 Coding for Cases of Hyperactivity and Aggression Box 4.2 Potential co-variates