Impact of air pollution on mental illness in early adulthood: Feasibility study combining UK twin cohort data with modelled air pollution exposure

空气污染是一个全球性的环境健康问题。暴露于高水平污染与一系列身体健康问题有关，包括心血管和呼吸系统疾病。最近的研究表明，空气污染也可能影响心理健康。然而，这些研究存在一些方法上的问题，因此很难就暴露于空气污染和心理健康问题之间的关系得出任何明确的结论。这一点很重要，因为抑郁症等精神疾病给个人、家庭和社会造成了巨大负担。如果我们了解是什么导致了它们的发展，那么我们就可以设计有效的干预措施，并引入政策（如降低污染水平）来防止它们的发生。此外，由于绝大多数精神疾病都是在成年早期开始的，因此必须关注这一时期之前的暴露，以最大限度地提高预防机会。因此，该项目将利用来自环境风险（E-Risk）纵向双胞胎研究的2000多名英国双胞胎的独特队列，并将他们在18岁时完成的深入临床评估与他们在前一年暴露于空气污染的高分辨率估计联系起来，以更全面地调查空气污染暴露对心理健康问题的潜在影响。具体而言，将在E-Risk参与者的居住地址周围以及他们报告在一年期间（2012年）花费大部分时间的其他两个地点估计一系列污染物的室外浓度，并将这些平均值用于产生三个地点的年度估计值。这些估计值将与过去一年的精神病诊断数据（焦虑，注意力缺陷多动障碍[ADHD]，抑郁症和行为障碍）相结合，这些数据是在18岁时的临床访谈中获得的。然后将检查污染暴露的估计水平与每种精神障碍之间的联系。这项研究建立在项目团队进行的一项小规模试点的基础上，该试点仅关注居住在伦敦地区的双胞胎，这表明将这些数据集联系起来是可行的，并表明空气污染暴露的估计水平与18岁时的抑郁症，行为障碍和ADHD有关。鉴于英国各地的污染水平差异很大，因此将这项初步工作扩展到整个英国样本非常重要。拟议的研究将在几个方面大大改进现有的研究。首先，我们将使用先进的估计模型，可以预测空气污染暴露到地址水平，这增加了估计暴露的准确性。其次，我们将使用来自英国各地的双胞胎儿童的大量特征良好的样本，这些儿童自出生以来就进行了广泛的评估，从而使我们能够检查空气污染和精神疾病是否与其他因素（例如，社会经济地位、吸烟、酗酒、身体疾病）。我们还将比较双胞胎中的一个暴露于高水平污染而另一个暴露于较低水平污染的精神疾病的发生率（由于生活在不同的地区），这使我们能够排除我们无法直接测量的遗传和环境因素，从而增加对我们发现的信心。污染估计的高分辨率和强大的孪生设计将保证该项目的结果大大促进我们对空气污染暴露在精神疾病发展中的作用的理解，从而使我们更接近预防。我们预计，该项目将为环境数据与英国广泛的队列数据的创新整合铺平道路。

Air pollution is a worldwide environmental health issue. Exposure to high levels of pollution has been linked to a range of physical health problems, including cardiovascular and respiratory illnesses. Recent research suggests that air pollution may also have an effect on mental health. However, these studies suffer from a number of methodological problems which make it difficult to draw any firm conclusions about the relationship between exposure to air pollution and mental health problems. This is important to ascertain as psychiatric disorders, such as depression, place a massive burden on individuals, families and society. If we understand what causes them to develop then we can design effective interventions and introduce policies (such as reducing pollution levels) to prevent them from occurring. Moreover, as the vast majority of all psychiatric disorders have started by early adulthood, it is essential to focus on exposure prior to this period to maximise prevention opportunities. Therefore, this project will capitalise on a unique cohort of over 2000 UK twins from the Environmental Risk (E-Risk) Longitudinal Twin study and link the in-depth clinical assessments completed on them at age 18 with high-resolution estimates of their exposure to air pollution in the previous year to investigate more comprehensively the potential impact of air pollution exposure on mental health problems. Specifically, outdoor concentrations for a range of pollutants will be estimated around the E-Risk participants' residential addresses together with two other locations they report spending the majority of their time at during a one-year period (2012) and these will be averaged to produce an annual estimate across the three locations. These estimates will be securely combined with data on past-year psychiatric diagnoses (anxiety, attention-deficit hyperactivity disorder [ADHD], depression, and conduct disorder) obtained on the participants during clinical interviews at age 18. Associations between the estimated level of pollution exposure and each psychiatric disorder will then be examined. This study builds on a smaller-scale pilot conducted by the project team focused just on twins who lived in the London area, which demonstrated that it was feasible to link such datasets and suggested that estimated levels of air pollution exposure were associated with depression, conduct disorder and ADHD at age 18. Given that pollution levels vary widely across the UK it is important to extend this initial work to the full UK sample. The proposed study will substantially improve upon existing studies in several ways. Firstly, we will use a cutting-edge estimation model that can predict air pollution exposure down to address level, which increases the accuracy of estimated exposure. Secondly, we will use a large well-characterised sample of twin children from across the UK who have been extensively assessed since birth thus enabling us to check that air pollution and psychiatric disorders are not spuriously associated due to other factors (e.g., socio-economic status, smoking, victimisation, physical illnesses). We will also compare the rates of psychiatric disorders in twins where one twin has been exposed to high levels of pollution and the other has been exposed to lower levels (due to living in different areas), which allows us to rule out genetic and environmental factors that we cannot measure directly thus increasing confidence in our findings.Overall, the quality of our densely-phenotyped cohort data, the high resolution of the pollution estimates, and powerful twin design, will guarantee the results of this project substantially advance our understanding of the role of air pollution exposure in the development of psychiatric disorders, thus moving us closer to prevention. We anticipate that this project will pave the way for additional innovative integrations of environmental data with the extensive cohort data available in the UK.