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ORIGINAL ARTICLE

Climate Change and Risk of Completed Suicide Caroline Dumont, MD,* Elizabeth Haase, MD,†‡ Trygve Dolber, MD,§ Janet Lewis, MD,|| and John Coverdale, MD, MEd¶

Abstract: Climate change is increasingly recognized as having multiple adDownloaded from http://journals.lww.com/jonmd by l8lgcFOoAXHnR5xSF7ruXMe506TYY7hR/WNmVOPTtsP6dMh/y7HuQRbUzljMSdFvOF5UR/ntk6KWm4Sipsk55QZoiTWELaiEK016Pj9yaHM= on 06/30/2020

verse mental health effects, many of which are just beginning to be understood. The elevated rates of suicides observed in some communities affected by climate change and rising rates of suicide in the United States as climate change intensifies have suggested the two may be associated. We searched PubMed and PsycInfo using the terms climate change and suicide, and provide here a review of the current literature on climate change and suicide that explores possible associations and methodological issues and challenges in this research. Key Words: Climate, suicide, mental health, psychiatry, environment, disasters (J Nerv Ment Dis 2020;208: 559–565)

ach year and throughout the world, more than 900,000 people die by suicide. In the United States alone, 14 of every 100,000 people died by suicide in 2017, making suicide the 10th leading cause of death in the United States (Murphy et al., 2018). This rate has increased by 33% since 1999 (Curtin and Hedegaard, 2019), and significantly increased from 2016 to 2017 (Murphy et al., 2018). It has increased for both males and females and for all ages 10 through 74 (Curtin and Hedegaard, 2017). Particular groups of concern include adolescents and young adults (Miron et al., 2019). Although a myriad of psychiatric, psychological, and cultural factors may be involved in the increasing rates of suicide, one less appreciated factor is the role of climate change. Climate change is increasingly recognized as having a profound impact on mental health. Populations especially vulnerable to climate change include the poor and homeless, children, the elderly, and the mentally ill (Berry et al., 2018; Bourque and Cunsolo Willox, 2014; Coverdale et al., 2018; Masson-Delmotte et al., 2018). Elevated rates of suicide have been observed in some communities affected by climate change (Hanigan et al., 2012). We searched PubMed and PsycInfo using the terms climate change and suicide, and found no overview of the different contributing factors that have linked climate change to suicide to date. In this article, therefore, we aim to explore the potential role of climate change in suicide rates and to describe the methodological issues and challenges in this research. There is significant value in correlating suicide rates with climate change, as it may be one indicator of psychic distress among those struggling at the front lines of a changing planet. As the quality of suicide data being reported improves globally (Bachmann, 2018), the outcomes of suicide prevention measures and climate adaptation efforts can be more accurately assessed. We advocate for an increased focus of attention and research on this important public health concern, because the prioritization of action on climate change by the psychiatric field requires good science and evidence.

*Yale School of Medicine, New Haven, Connecticut; †University of Nevada School of Medicine, Reno; ‡Outpatient Behavioral Health, Carson Tahoe Regional Medical Center, Carson City, Nevada; §Emory University School of Medicine, Atlanta, Georgia; ||University of Rochester, Finger Lakes Health, Geneva, New York; and ¶Meninger Department of Psychiatry and Center for Ethics, Baylor School of Medicine, Houston, Texas. Send reprint requests to Elizabeth Haase, MD, University of Nevada School of Medicine, 5190 Neil Rd, Reno, NV 89502. E‐mail: ehaase@me.com. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved. ISSN: 0022-3018/20/20807–0559 DOI: 10.1097/NMD.0000000000001162

This review addresses four aspects of anthropogenic climate change and associated findings on suicide rates: 1) air pollution from the burning of fossil fuels, fire smoke, and ozone production; 2) higher temperatures, including ambient temperature and increased frequency of heat waves; 3) habitat changes linked to rising global temperature, including changes in landscape, food source, plant and animal life, and drought; and 4) impacts of ocean warming, including more frequent natural disasters, sea level rise, and associated predicted mass migration. We also include suicide that appears to have arisen directly from a psychological reaction to these climate realities. For the purposes of this review, we do not include changes in suicide associated with the changing epidemiology of infectious diseases and soil-based changes in nutrition. Although changes in the geographical distribution and prevalence of nutritional and infectious disorders will likely influence the rates of suicidal behavior associated with these illnesses, these novel habitat-illness interactions have not yet been studied. Our description here of the literature is not exhaustive but highlights a range of studies with both positive and negative findings to demonstrate the state of the field and suggest areas for further research.

ASSOCIATION OF SUICIDE RATES WITH AIR POLLUTION Air pollution is defined by the EPA in terms of six criteria pollutants: lead, ozone, carbon monoxide, nitrogen oxide, particulate matter, and sulfur dioxide. The burning of fossil fuels is considered to be the source of 81% (Philip et al., 2014) of these pollutants. Particulate matter air pollution, defined based on particle sizes of 2.5 μm (PM2.5), 10 μm (PM10), and ultrafine particles (UFPs), now has a robust literature of association with adverse health and mental health effects. Particulate air pollution has been shown to translocate to the brain via olfactory and pulmonary nerves as well as the vascular system, where it causes multiple pathological changes in neurons and glia (Wright and Ding, 2016). As with any climate variable, studying the effects of a particular element of air pollution on the brain is complex, and scientists must delineate each from other types of air pollution and from other air factors, such as seasonal variations in wind flow, fires, dust, pollen, temperature, moisture, and sunshine. Particulate matter and the criteria pollutants ozone, sulfur dioxide, and nitrogen oxide have been the most studied for their mental health impacts. All have been associated either with a direct increase in suicide risk or with neuropsychiatric conditions known to increase suicidality: autism (Volk et al., 2013), dementia (Cacciottolo et al., 2017), depression (Gu et al., 2019; Kioumourtzoglou et al., 2017), and bipolar disorder (Khan et al., 2019). Increased suicide risk and increased rates of neuropsychiatric disorders associated with suicide have also been found under a variety of spatial and temporal conditions, including proximity to coal plants, traffic, and freeways, and chronic and acute air pollution events (Cacciottolo et al., 2017; Gu et al., 2019; Khan et al., 2019; Perera, 2017; Volk et al., 2013). Overall, studies have revealed increased suicide rates of 1% to 2% per day of poor-quality air. It is important, however, for psychiatrists to feel secure with the depth and breadth of the science supporting a link of air pollution to mental disorders (reviewed in Buoli et al., 2018), as it

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