Exposure to trauma is pervasive in societies worldwide and is associated with substantial costs to the individual and society, making it a significant global public health concern. We present evidence for trauma as a public health issue by highlighting the role of characteristics operating at multiple levels of influence – individual, relationship, community, and society – as explanatory factors in both the occurrence of trauma and its sequelae. Within the context of this multi-level framework, we highlight targets for prevention of trauma and its downstream consequences and provide examples of where public health approaches to prevention have met with success. Finally, we describe the essential role of public health policies in addressing trauma as a global public health issue, including key challenges for global mental health and next steps for developing and implementing a trauma-informed public health policy agenda. A public health framework is critical for understanding risk and protective factors for trauma and its aftermath operating at multiple levels of influence and generating opportunities for prevention.

1. Public health impact of trauma Exposure to trauma is pervasive in societies worldwide. Population-based data from various countries indicate that a majority of adults will experience a traumatic event at some point in their lives, despite cross-national variation in the prevalence of specific types of traumatic events (Benjet et al., 2016 Benjet, C., Bromet, E., Karam, E. G., Kessler, R. C., McLaughlin, K. A., Ruscio, A. M., … Koenen, K. C. (2016). The epidemiology of traumatic event exposure worldwide: Results from the World Mental Health Survey Consortium. Psychological Medicine, 46(2), 1–9. doi:10.1017/s0033291715001981; Burri & Maercker, 2014 Burri, A., & Maercker, A. (2014). Differences in prevalence rates of PTSD in various European countries explained by war exposure, other trauma and cultural value orientation. BMC Research Notes, 7(1), 407. doi:10.1186/1756-0500-7-407). Trauma exposure is also common in children and adolescents around the world. A substantial proportion of children globally are exposed to trauma as a result of armed conflict, natural disasters, and other humanitarian emergencies (World Health Organization, 2013b World Health Organization. (2013b). Mental health action plan 2013-2020. Geneva: World Health Organization.). An estimated 230 million children currently live in countries impacted by armed conflicts (UNICEF, 2014 UNICEF. (2014). With 15 million children caught up in major conflicts, UNICEF declares 2014 a devastating year for children [Press release]. Retrieved from http://www.unicef.org/media/media_78058.html?p=printme), which increases risk of experiencing displacement, witnessing violence and death, and being orphaned, kidnapped, raped, or recruited as child soldiers (UNICEF, 2009 UNICEF. (2009). Machel study 10-year strategic review: Children and conflict in a changing world. New York: Office of the Special Representative of the Secretary-General for Children, & Armed Conflict.). Traumatic events do not only occur at random, but can be influenced by individual characteristics, peer group relationships, community characteristics, and socio-political factors. At the individual level, for example, the likelihood of experiencing particular types of trauma varies by sex, age, race/ethnicity, and sexual orientation (Garcia-Moreno, Jansen, Ellsberg, Heise, & Watts, 2006 Garcia-Moreno, C., Jansen, H. A. F. M., Ellsberg, M., Heise, L., & Watts, C. (2006). WHO Multi-country study on women’s health and domestic violence against women. Lancet, 368, 1260–1269. doi:10.1016/S0140-6736(06)69523-8; Kessler, Sonnega, Bromet, Hughes, & Nelson, 1995 Kessler, R. C., Sonnega, A., Bromet, E., Hughes, M., & Nelson, C. B. (1995). Posttraumatic stress disorder in the National Comorbidity Survey. Archives of General Psychiatry, 52, 1048–1060.; McLaughlin et al., 2013 McLaughlin, K. A., Koenen, K. C., Hill, E., Petukhova, M., Sampson, N. A., Zaslavsky, A., & Kessler, R. C. (2013). Trauma exposure and posttraumatic stress disorder in a US national sample of adolescents. Journal of the American Academy of Child & Adolescent Psychiatry, 52, 815–830. doi:10.1016/j.jaac.2013.05.011; Rees et al., 2011 Rees, S., Silove, D., Chey, T., Ivancic, L., Steel, Z., Creamer, M., … Forbes, D. (2011). Lifetime prevalence of gender-based violence in women and the relationship with mental disorders and psychosocial function. JAMA: Journal of the American Medical Association, 306, 513–521.). Community and socio-political factors also influence the likelihood of trauma occurrence across geographic locations. Certain types of traumas (e.g. violence) are more likely to occur in certain locations (e.g. metropolitan areas and conflict zones) (McLaughlin et al., 2013 McLaughlin, K. A., Koenen, K. C., Hill, E., Petukhova, M., Sampson, N. A., Zaslavsky, A., & Kessler, R. C. (2013). Trauma exposure and posttraumatic stress disorder in a US national sample of adolescents. Journal of the American Academy of Child & Adolescent Psychiatry, 52, 815–830. doi:10.1016/j.jaac.2013.05.011; Perkonigg, Kessler, Storz, & Wittchen, 2000 Perkonigg, A., Kessler, R. C., Storz, S., & Wittchen, H.-U. (2000). Traumatic events and post-traumatic stress disorder in the community: Prevalence, risk factors, and comorbidity. Acta Psychiatrica Scandinavica, 101, 46–59.). Moreover, different communities will have diverse trauma recovery trajectories based on their pre-trauma community characteristics (Nakagawa & Shaw, 2004 Nakagawa, Y., & Shaw, R. (2004). Social capital: A missing link in disaster recovery. International Journal of Mass Emergencies and Disasters, 22, 5–34.). Thus, it is important not to overlook these characteristics in considering both trauma exposure and outcome. The public health impact of trauma exposure is staggering for both communities and individuals. Catastrophic events such as natural and man-made disasters and terrorist attacks can have devastating effects on the social fabric of society and communities, not only involving injuries and loss of life, but also related to property destruction and infrastructure damage. This aftermath, coupled with high levels of resulting migration, can create prolonged disruption in the delivery of social services and the dissolution of social support networks. These community-level consequences can persist for lengthy periods, often fundamentally changing the physical and social landscape of a community (Galea et al., 2002 Galea, S., Ahern, J., Resnick, H., Kilpatrick, D. G., Bucuvalas, M., Gold, J., & Vlahov, D. (2002). Psychological sequelae of the September 11 terrorist attacks in New York city. New England Journal of Medicine, 346, 982–987. doi:10.1056/NEJMsa013404; Hollifield et al., 2008 Hollifield, M., Hewage, C., Gunawardena, C. N., Piyadasa, K., Bopagoda, K., & Weerarathnege, K. (2008). Symptoms and coping in Sri Lanka 20-21 months after the 2004 tsunami. British Journal of Psychiatry, 192, 39–44. doi:10.1192/bjp.bp.107.038422; Rosenbaum, 2006 Rosenbaum, S. (2006). US health policy in the aftermath of Hurricane Katrina. JAMA: Journal of the American Medical Association, 295, 437–440. doi:10.1001/jama.295.4.437). Low and middle income countries (LMICs) are disproportionately affected. Collective violence (e.g. war, genocide) is 10 times more common in LMICs versus high income countries (HICs) (World Health Organization, 2002 Krug, E., G., Dahlberg, L. L., Mercy, J. A., Zwi, A., & Lozano, R. (Eds.). (2002). World report on violence and health. Geneva: World Health Organization.), and LMICs carry the brunt of migration problems caused by disasters and violence. In 2015, 65.3 million people were forcibly displaced, the vast majority from LMICs. According to the United Nations High Commission for Refugees (UNHCR), the top hosting countries are Turkey (2.5 million), Pakistan (1.6 million), Lebanon (1.1 million), and Iran (1.0 million). Exposure to trauma is particularly detrimental when it occurs in childhood or adolescence, disrupting numerous aspects of development in cognitive, emotional, and social domains, leading to adverse mental health and educational outcomes (Cicchetti & Toth, 1995 Cicchetti, D., & Toth, T. L. (1995). A developmental psychopathology perspective on child abuse and neglect. Journal of the American Academy of Child & Adolescent Psychiatry, 34, 541–565. doi:10.1097/00004583-199505000-00008; Koenen, Moffit, Caspi, Taylor, & Purcell, 2003 Koenen, K. C., Moffit, T. E., Caspi, A., Taylor, A., & Purcell, S. (2003). Domestic violence is associated with environmental suppression of IQ in young children. Development and Psychopathology, 15, 297–311.) with long-term consequences for learning and memory (Teicher, Anderson, & Polcari, 2012 Teicher, M. H., Anderson, C. M., & Polcari, A. (2012). Childhood maltreatment is associated with reduced volume in the hippocampal subfields CA3, dentate gyrus, and subiculum. Proceedings of the National Academy of Sciences, 109, E563–572. doi:10.1073/pnas.1115396109), emotional functioning (De Bellis et al., 1994 De Bellis, M. D., Chrousos, G. P., Dorn, L. D., Burke, L., Helmers, K., Kling, M. A., & Trickett, P. K. (1994). Hypothalamic-pituitary-adrenal axis dysregulation in sexually abused girls. Journal of Clinical Endocrinology and Metabolism, 78, 249–255. doi:10.1210/jcem.78.2.8106608; McCrory et al., 2011 McCrory, E. J., De Brito, S. A., Sebastian, C. L., Mechelli, A., Bird, G., Kelly, P. A., & Viding, E. (2011). Heightened neural reactivity to threat in child victims of family violence. Current Biology, 21, R947–948. doi:10.1016/j.cub.2011.10.015; McLaughlin & Hatzenbuehler, 2009 McLaughlin, K. A., & Hatzenbuehler, M. L. (2009). Mechanisms linking stressful life events and mental health problems in a prospective, community-based sample of adolescents. Journal of Adolescent Health, 44, 153–160. doi:10.1016/j.jadohealth.2008.06.019; Pollak & Sinha, 2002 Pollak, S. D., & Sinha, P. (2002). Effects of early experience on children’s recognition of facial displays of emotion. Development and Psychopathology, 38, 784–791.; Pollak, Vardi, Putzer Bechner, & Curtin, 2005 Pollak, S. D., Vardi, S., Putzer Bechner, A. M., & Curtin, J. J. (2005). Physically abused children’s regulation of attention in response to hostility. Child Development, 76, 968–977. doi:10.1111/j.1467-8624.2005.00890.x), social relationships, elevated risk of re-victimization (Cole & Putnam, 1992 Cole, P. M., & Putnam, F. W. (1992). Effect of incest on self and social functioning: A developmental psychopathology perspective. Journal of Consulting and Clinical Psychology, 60, 174–184.; DiLillo, 2001 DiLillo, D. (2001). Interpersonal functioning among women reporting a history of childhood sexual abuse: Empirical findings and methodological issues. Clinical Psychology Review, 21, 553–576.; Follette, Polusney, Bechtle, & Naugle, 1996 Follette, V., Polusney, M. A., Bechtle, A. E., & Naugle, A. E. (1996). Cumulative trauma: The impact of child sexual abuse, adult sexual assault, and spouse abuse. Journal of Traumatic Stress, 9, 25–35.), and mental disorders (Kilpatrick et al., 2003 Kilpatrick, D. G., Ruggiero, K. J., Acierno, R., Saunders, B. E., Resnick, H. S., & Best, C. L. (2003). Violence and risk of PTSD, major depression, substance abuse/dependence, and comorbidity: Results from the National Survey of Adolescents. Journal of Consulting and Clinical Psychology, 71, 692–700.; McLaughlin et al., 2012 McLaughlin, K. A., Green, J. G., Gruber, M. J., Sampson, N. A., Zaslavsky, A., & Kessler, R. C. (2012). Childhood adversities and first onset of psychiatric disorders in a national sample of adolescents. Archives of General Psychiatry, 69, 1151–1160. doi:10.1001/archgenpsychiatry.2011.2277, 2013 McLaughlin, K. A., Koenen, K. C., Hill, E., Petukhova, M., Sampson, N. A., Zaslavsky, A., & Kessler, R. C. (2013). Trauma exposure and posttraumatic stress disorder in a US national sample of adolescents. Journal of the American Academy of Child & Adolescent Psychiatry, 52, 815–830. doi:10.1016/j.jaac.2013.05.011). Post-traumatic stress disorder (PTSD), which is inextricably linked with trauma, is in itself a profound public health burden. Individuals who develop PTSD following trauma experience impaired role functioning and reduced life course opportunities (Kessler, 2000 Kessler, R. C. (2000). Posttraumatic stress disorder: The burden to the individual and to society. Journal of Clinical Psychiatry, 61(suppl. 5), 4–12.). PTSD was associated with high levels of disability, and in developing countries disability associated with PTSD was higher than most common medical conditions except for headaches and chronic pain (Ormel et al., 2008 Ormel, J., Petukhova, M., Chatterji, S., Aguilar-Gaxiola, S., Alonso, J., Angermeyer, M. C., … Kessler, R. C. (2008). Disability and treatment of specific mental and physical disorders across the world. British Journal of Psychiatry, 192, 368–375. doi:10.1192/bjp.bp.107.039107). The economic costs of PTSD are staggering, with work impairment associated with the disorder estimated at 3.6 days per month per person with PTSD. The annual lost productivity due to PTSD is estimated at over $3 billion dollars in the U.S. alone (Kessler, 2000 Kessler, R. C. (2000). Posttraumatic stress disorder: The burden to the individual and to society. Journal of Clinical Psychiatry, 61(suppl. 5), 4–12.). Because the development of PTSD is conditional on trauma exposure, PTSD may be the most preventable of mental disorders. We have the unique opportunity to reduce the population burden of PTSD both by preventing trauma exposure and by delivering timely interventions in the wake of trauma to those most at risk. The following sections explore these opportunities based on a public health approach, extending previous work (Magruder, Kassam-Adams, Thoresen, & Olff, 2016 Magruder, K. M., Kassam-Adams, N., Thoresen, S., & Olff, M. (2016). Prevention and public health approaches to trauma and traumatic stress: A rationale and call to action. European Journal of Psychotraumatology, 7, 29715. doi:10.3402/ejpt.v7.29715) by expanding examples and policy implications.

2. Public health model of traumatic stress Current approaches to public health are explicitly multi-level and concerned with identifying causes of health states (Krieger, 1994 Krieger, N. (1994). Epidemiology and the web of causation: Has anyone seen the spider? Social Science and Medicine, 39, 887–903.; Susser, 1998 Susser, M. (1998). Does risk factor epidemiology put epidemiology at risk? Peering into the future. Journal of Epidemiology and Community Health, 52, 608–611.) with the ultimate goal of preventing disease onset. With problems that have a behavioural component, a public health model encompasses factors operating at multiple levels of influence, such as family, school, and cultural levels (see Figure 1) (Bronfenbrenner, 1979 Bronfenbrenner, U. (1979). The ecology of human development: Experiments by nature and design. Cambridge, MA: Harvard University Press.) (Dahlberg & Krug, 2002 Dahlberg, L. L., & Krug, E. G. (2002). Violence: A global public health problem. In E. Krug, L. L. Dahlberg, J. A. Mercy, & R. Lozano (Eds.), World report on violence and health (pp. 1–56). Geneva, Switzerland: World Health Organization.). Trauma is a public health issue 标题：创伤是一个公共健康问题 El trauma es un problema de salud pública All authors Kathryn M. Magruder Katie A. McLaughlin Diane L. Elmore Borbon https://doi.org/10.1080/20008198.2017.1375338 Figure 1. The social-ecological model, a framework for prevention from the U.S. centers for disease control and prevention (Dahlberg & Krug, 2002 Dahlberg, L. L., & Krug, E. G. (2002). Violence: A global public health problem. In E. Krug, L. L. Dahlberg, J. A. Mercy, & R. Lozano (Eds.), World report on violence and health (pp. 1–56). Geneva, Switzerland: World Health Organization.). Display full size Figure 1. The social-ecological model, a framework for prevention from the U.S. centers for disease control and prevention (Dahlberg & Krug, 2002 Dahlberg, L. L., & Krug, E. G. (2002). Violence: A global public health problem. In E. Krug, L. L. Dahlberg, J. A. Mercy, & R. Lozano (Eds.), World report on violence and health (pp. 1–56). Geneva, Switzerland: World Health Organization.). In the case of trauma-related problems, the important components are the trauma itself, those who are exposed to trauma, their relationships, the variety of environmental factors playing a role in shaping the likelihood of both trauma exposure and outcome, and societal factors, attitudes, and characteristics that influence trauma likelihood and intervention. Such a multi-level approach provides a public health framework for developing an array of strategies aimed at preventing the occurrence and sequelae of trauma. Furthermore, these levels can be considered as points of intervention and opportunities for prevention. The classic prevention framework includes three levels: primary; secondary; and tertiary (Commission on Chronic Illness, 1957 Commission on Chronic Illness. (1957). Chronic illness in the USA (Vol. 1). Cambridge, MA: Harvard University Press.). The aim of primary prevention is to prevent the actual occurrence of the disease or illness. The purpose of secondary prevention is to intervene early in the disease process for cure or optimal outcomes. Tertiary prevention is aimed at preventing the disability that accompanies an illness or disease. Each of these levels of prevention can be implemented at different system levels, including society at large, the community, the family, and the individual. Subsequently, risk and protective factors can be translated into multi-sectoral, multi-modal, and multi-level preventive interventions (De Jong, 2010 De Jong, J. T. (2010). A public health framework to translate risk factors related to political violence and war into multilevel preventive interventions. Social Science & Medicine, 70, 71–79. doi:10.1016/j.socscimed.2009.09.044; Wiist et al., 2014 Wiist, W. H., Barker, K., Arya, N., Rohde, J., Donohoe, M., White, S., … Hagopian, A. (2014). The role of public health in the prevention of war: Rationale and competencies. American Journal of Public Health, 104, e34–e37. doi:10.2105/AJPH.2013.301778). Table 1 provides a few examples of prevention strategies at each level. Trauma is a public health issue 标题：创伤是一个公共健康问题 El trauma es un problema de salud pública All authors Kathryn M. Magruder Katie A. McLaughlin Diane L. Elmore Borbon https://doi.org/10.1080/20008198.2017.1375338 Table 1. Prevention examples within a public health framework. CSVDisplay Table From a public health perspective, preventing exposure to trauma is an obvious strategy, and such efforts can be targeted to all levels of the social-ecological model. A number of strategies are aimed at reducing the likelihood of trauma exposure in individuals. Alcohol education programmes for young adults, such as those implemented on U.S. college campuses, can reduce high-risk drinking which in turn may reduce exposure to traumatic events like physical and sexual assaults, accidents, or motor vehicle accidents (Katz & Moore, 2013 Katz, J., & Moore, J. (2013). Bystander education training for campus sexual assault prevention: An initial meta-analysis. Violence and Victims, 28, 1054–1067.). At the relationship level, there are programmes to strengthen the abilities and sensitivity of family caregivers as well as programmes to prevent bullying in schools. At the community level, examples include lighting parking lots, streets, and campuses to prevent crime. Even design of highways to reduce traffic accidents can be seen as an environmental response to reduce motor vehicle accidents and thus reduce trauma occurrence. Other examples include neighbourhood watch programmes to prevent crime and community members preventing sexual assaults in refugee camps. At the societal level, some traumas can be prevented by promoting appropriate social norms. For example, policy changes in Australia have been successful at reducing firearms deaths and injuries (Chapman, Alpers, Agho, & Jones, 2006 Chapman, S., Alpers, P., Agho, K., & Jones, M. (2006). Australia’s 1996 gun law reforms: Faster falls in firearm deaths, firearm suicides, and a decade without mass shootings. Injury Prevention, 12, 365–372. doi:10.1136/ip.2006.013714). Because alcohol consumption is price sensitive, especially for those under 21 years old in the U.S., changes in pricing of alcohol have been proposed as a means of reducing hazardous drinking, and thereby reducing alcohol-related traumatic events, such as family violence and crimes (Chaloupka, 1993 Chaloupka, F. J. (1993). Effects of price on alcohol-related problems. Alcohol Health Research World, 17, 46–53.; Chaloupka, Grossman, & Saffer, 1998 Chaloupka, F. J., Grossman, M., & Saffer, H. (1998). The effects of price on the consequences of alcohol use and abuse. In M. Galanter (Ed.), Recent developments in alcoholism, Vol 14: The consequences of alcoholism (pp. 331–346). New York: Plenum Press.; Presley, Meilman, & Leichliter, 2002 Presley, C. A., Meilman, P. W., & Leichliter, J. S. (2002). College factors that influence drinking. Journal of Studies on Alcohol, 14, 89–90.). Many targets are not thought of as trauma prevention even though they serve as such, for example, increased screening at airports and at major events (e.g. World Cup). Even seemingly unrelated approaches such as improving education levels, eradicating poverty, and decreasing social inequality may have positive primary prevention outcomes because these factors are important predictors of health, mental health, and human rights (Daar et al., 2007 Daar, A. S., Singer, P. A., Persad, D. L., Pramming, S. K., Matthews, D. R., Beaglehole, R., … Bell, J. (2007). Grand challenges in chronic non-communicable diseases. Nature, 450, 494–496. doi:10.1038/450494a). From some of these examples, it is clear that efforts aimed at preventing trauma may have multiple beneficial outcomes. In the case of reducing the number of motor vehicle accidents, physical trauma and death are the primary targets, and psychological sequelae are the secondary. The same is true of the United Nations’ (UN) efforts to decrease political violence, to install war tribunals and prosecute perpetrators, and to stimulate efforts to have international laws which condemn human rights violations or ban landmines, or similarly when governments attempt to prevent mass terrorist attacks or the re-emergence of violence. Disaster preparedness training can also have a preventive effect, such as setting quality standards for buildings in earthquake- or landslide-prone areas or river beds, setting higher quality standards for the construction of nuclear power stations, providing better access to land in areas with landslides, creating better alarm systems for floods, cyclones, or hurricanes, and providing sheltered areas and evacuation plans in regions that are hit by volcano eruptions or typhoons (De Jong, 2011 De Jong, J. T. (2011). Disaster public mental health. In D. J. Stein, M. Friedman, & C. Blanco (Eds.), Post-traumatic stress disorder (pp. 217–262). Oxford: John Wiley and Sons.). Secondary prevention can also be directed at various levels. Early intervention with those who have been trauma exposed and are symptomatic focuses on individuals within various settings and environments (rather than focusing on environments per se). There is evidence that for those exposed to trauma and disasters, ongoing non-traumatic stressors are also predictive of PTSD onset and course (as well as for other problems, such as alcohol use disorders) (Cerdá et al., 2013 Cerdá, M., Bordelois, P. M., Galea, S., Norris, F. H., Tracy, M., & Koenen, K. C. (2013). The course of posttraumatic stress symptoms and functional impairment following a disaster: What is the lasting influence of acute versus ongoing traumatic events and stressors? Social Psychiatry and Psychiatric Epidemiology, 48, 385–395. doi:10.1007/s00127-012-0560-3, 2014 Cerdá, M., Richards, C., Cohen, G. H., Calabrese, J. R., Liberzon, I., Tamburrino, M., … Koenen, K. C. (2014). Civilian stressors associated with alcohol use disorders in the national guard. American Journal of Preventive Medicine, 47, 461–466. doi:10.1016/j.amepre.2014.06.015). Thus, minimization of these ongoing stressors may prevent the onset of PTSD and other psychiatric disorders. In fact, humanitarian relief operations aimed at large populations often focus on shelter, food, water, sanitation, and physical disease control. Evidence suggests that individual-level secondary prevention interventions aimed at bolstering resilience and reducing the likelihood of adverse effects following trauma are effective. For example, the military in several countries have developed pre-deployment programmes to prevent PTSD (Hourani, Council, Hubal, & Strange, 2011 Hourani, L. L., Council, C. L., Hubal, R. C., & Strange, L. B. (2011). Approaches to the primary prevention of posttraumatic stress disorder in the military: A review of the stress control literature. Military Medicine, 176, 721–730.), and a recent meta-analysis suggests that intervention within one month can be effective in children and adolescents following a single trauma exposure (Kramer & Landolt, 2011 Kramer, D. N., & Landolt, M. A. (2011). Characteristics and efficacy of early psychological interventions in children and adolescents after single trauma: A meta-analysis. European Journal of Psychotraumatology, 2. doi:10.3402/ejpt.v2i0.7858). At the relationship level, examples include shelters for survivors of domestic violence, interventions aimed at couples where domestic violence has already occurred, and foster care for children who are abused or neglected and unable to live with their parents or another relative. Some secondary prevention approaches focus on communities. For example, community support, as in the case of vigils for survivors and their families following disasters or mass violence, is often seen as helpful. Safety considerations, such as providing food and shelter and reuniting families post-disaster, may go a long way to reassure disaster survivors and prevent the development of mental health symptoms. Such support and intervention does not occur successfully in poorly organized or disenfranchised communities; thus, efforts to develop and promote strong proactive communities and build capacity to respond to disasters can also be seen as secondary prevention (Laborde, Magruder, Caye, & Parrish, 2013 Laborde, D. J., Magruder, K. M., Caye, J., & Parrish, T. B. (2013). Feasibility of disaster mental health preparedness training for Black communities. Disaster Medicine and Public Health Preparedness, 7, 303–312. doi:10.1001/dmp.2012.18). From the societal point of view, policies that promote early intervention are also helpful as secondary prevention measures. With the aim of preventing the progression of disease and disability, most tertiary prevention programmes are squarely in the clinical arena and are seen as part of standard treatment for PTSD or other trauma-related mental health problems; however, there are some examples of societal level tertiary prevention. For example, in the international arena tertiary prevention may aim at peace-keeping and peace-enforcing troops, as well as peace agreements to prevent the reemergence of political violence. Lower rates of PTSD have been found in states that have legislated legal protections for lesbian, gay, bisexual, and transgendered individuals as compared to states that do not have protective legislation (Hatzenbuehler, McLaughlin, Keyes, & Hasin, 2010 Hatzenbuehler, M. L., McLaughlin, K. A., Keyes, K. M., & Hasin, D. S. (2010). The impact of discriminatory laws on psychiatric disorders in LGB populations: A prospective study. American Journal of Public Health, 100, 452–459. doi:10.2105/AJPH.2009.168815). Similarly, promotion of reconciliation and mediation skills between groups on the community level may be seen as tertiary prevention (De Jong, 2011 De Jong, J. T. (2011). Disaster public mental health. In D. J. Stein, M. Friedman, & C. Blanco (Eds.), Post-traumatic stress disorder (pp. 217–262). Oxford: John Wiley and Sons.). On the family and personal level, most tertiary prevention programmes aim at preventing the progression of disease and disability, and are seen as part of standard treatment for PTSD or other trauma-related mental health problems. Recasting traumatic stress treatment as an approach to prevent the development of comorbidities (e.g. depression and substance use disorders) and to improve functioning (even if not eliminating symptoms entirely) may open the door for novel clinical approaches. For example, the use of support dogs may improve functioning and reduce disability by enabling someone with traumatic stress to enjoy greater societal participation – even if symptoms are not completely alleviated (Krause-Parello, Sami, & Padden, 2016 Krause-Parello, C. A., Sami, S., & Padden, E. (2016). Military veterans and canine assistance for post-traumatic stress disorder: A narrative review of the literature. Nurse Education Today, 47, 43–50. doi:10.1016/j.nedt.2016.04.020). At the relationship level, there is evidence that training foster parents of children with significant psychological problems resulting from trauma exposure may help to prevent the development of additional problems (Leve et al., 2012 Leve, L. D., Harold, G. T., Chamberlain, P., Landsverk, J. A., Fishe, R. P. A., & Vostanis, P. (2012). Practitioner review: Children in foster care–vulnerabilities and evidence-based interventions that promote resilience processes. Journal of Child Psychology and Psychiatry,And Allied Disciplines, 53(12), 1197–1211. doi:10.1111/j.1469-7610.2012.02594.x). As with secondary prevention, both community and societal support can also be helpful. They can help to establish service availability and to promote use of services by reducing stigma.

3. The essential role of public health policies Effective public policies can help to shape societal norms concerning public health issues and are ideally informed by an evidence base. Such policies have been critical in securing the 10 great public health achievements of the twenty-first century, including tobacco control, motor vehicle safety, and prevention and control of infectious diseases (Centers for Disease Control and Prevention, 2011 Centers for Disease Control and Prevention. (2011). Ten great public health achievements: United States 2001-2010. Morbidity and Mortality Weekly Report, 60, 619–623.). Policies must focus on preventing traumatic events, when possible, providing early intervention services for survivor communities at risk of poor post-trauma outcomes, and reducing stigma. There are currently several overarching mental health policy challenges facing communities and countries plagued by violence and trauma. Because trauma and mental health issues are inextricably linked, they also share many challenges. Mental health issues (and thus trauma-related issues) have largely been ignored as a priority in the global public health agenda (Saracena et al., 2007 Saracena, B., van Ommeren, M., Batniji, R., Cohen, A., Gureje, O., Mahoney, J., … Underhill, C. (2007). Barriers to improvement of mental health services in low-income and middle-income countries. Lancet, 370, 1164–1174. doi:10.1016/S0140-6736(07)61263-X; Saxena & Skeen, 2012 Saxena, S., & Skeen, S. (2012). No health without mental health: Challenges and opportunities in global mental health. African Journal of Psychiatry, 15, 397–400.). For example, the UN Millennium Development Goals (MDGs), a set of development targets agreed to by the international community, failed to include any specific focus on mental health or trauma (Saxena & Skeen, 2012 Saxena, S., & Skeen, S. (2012). No health without mental health: Challenges and opportunities in global mental health. African Journal of Psychiatry, 15, 397–400.). The main focus of the recent World Health Organization (WHO) Global Action Plan for the Prevention and Control of NCDs is on four specific types – cardiovascular diseases, cancer, chronic respiratory diseases, and diabetes – and on four shared behavioural risk factors – tobacco use, unhealthy diet, physical inactivity, and harmful use of alcohol. Among the other conditions of public health importance that are explicitly mentioned in the plan are mental disorders, violence, and injuries (World Health Organization, 2013a World Health Organization. (2013a). Global action plan for the prevention and control of noncommunicable diseases 2013-2020. Geneva: World Health Organization.). This indicates that mental health is beginning to gain impetus alongside other leading public health policy priorities; however, until full parity exists for mental health concerns, the issue of preventing trauma and intervening early in its aftermath will fail to receive sufficient global attention as a policy priority. Much work remains ahead to understand the nature and treatment of mental disorders in global context. Greater investment is needed in global mental health research in high, middle, and low income countries. Cross-national population-based initiatives, such as the World Mental Health Surveys, can play an important role in understanding the prevalence, impact, and health systems’ response to mental disorders (Patel, 2012 Patel, V. (2012). Global mental health: From science to action. Harvard Review of Psychiatry, 20, 6–12. doi:10.3109/10673229.2012.649108). More research is needed to comprehend the broad physical health, mental health, and developmental impacts of childhood polyvictimization (Felitti et al., 1998 Felitti, V. J., Anda, R. F., Nordenberg, D., Williamson, D. F., Spitz, A. M., Edwards, V., … Marks, J. S. (1998). Relationship of childhood abuse and household dysfunction to many of the leading causes of death in adults: The Adverse Childhood Experiences (ACE) Study. American Journal of Preventive Medicine, 14, 245–258.; Finkelhor, Ormrod, & Turner, 2007 Finkelhor, D., Ormrod, R. K., & Turner, H. A. (2007). Poly-victimization: A neglected component in child victimization. Child Abuse & Neglect, 31, 7–26. doi:10.1016/j.chiabu.2006.06.008). Additional priorities for improving global mental health research include a focus on adequately training researchers around the world, ensuring a bi-directional flow of information and partnerships in the global mental health research community (Patel & Prince, 2010 Patel, V., & Prince, M. (2010). Global mental health: A new global health field comes of age. JAMA: Journal of the American Medical Association, 303, 1976–1977. doi:10.1001/jama.2010.616). Recommendations for building global trauma research capacity include: providing quality training and distance learning opportunities, supporting international fellowships, promoting memberships in collaborative research teams, improving accessibility of the scientific literature, and encouraging researchers to share their knowledge with policymakers and key stakeholders (Fodor et al., 2014 Fodor, K. E., Unterhitzenberger, J., Chou, C. Y., Kartal, D., Leistner, S., Milosavljevic, M., … Alisic, E. (2014). Is traumatic stress research global? A bibliometric analysis. European Journal of Psychotraumatology, 5, 23269. doi:10.3402/ejpt.v5.23269). Unlike other service sectors that rely heavily on equipment or supplies, mental health services are primarily dependent on human resources (World Health Organization, 2011 World Health Organization. (2011). Human resources for mental health: Workforce shortages in low- and middle-income countries. Retrieved from http://whqlibdoc.who.int/publications/2011/9789241501019_eng.pdf?ua=1). Many have identified shortcomings of the current global mental health workforce, including limitations on the number and types of workers trained in mental health care, perhaps due to poor working conditions and low status associated with the mental health professions (Saracena et al., 2007 Saracena, B., van Ommeren, M., Batniji, R., Cohen, A., Gureje, O., Mahoney, J., … Underhill, C. (2007). Barriers to improvement of mental health services in low-income and middle-income countries. Lancet, 370, 1164–1174. doi:10.1016/S0140-6736(07)61263-X). According to WHO, an immediate and sizeable investment is needed to scale up a well-trained global mental health workforce. One method suggested for expanding the workforce is task shifting, or redistribution of tasks from highly qualified health workers to health workers with shorter training and fewer qualifications (World Health Organization, 2008 WHO, PEPFAR, UNAIDS. (2008). Task shifting: Rational redistribution of tasks among health workforce teams. Global recommendations and guidelines. Geneva: World Health Organization.). An example of a task shifting approach is WHO’s Problem Management Plus, a low-intensity intervention for adults with symptoms of common mental health problems. This intervention uses lay helpers supervised by skilled mental health professionals in communities exposed to adversity (Dawson et al., 2015 Dawson, K. S., Bryant, R. A., Harper, M., KuoweiTay, A., Rahman, A., Schafer, A., & Van Ommeren, M. (2015). Problem management plus (PM+): A WHO transdiagnostic psychological intervention for common mental health problems. World Psychiatry, 14(3), 354–357. doi:10.1002/wps.20255). In addition to more general mental health workforce strategies, several important efforts are underway by leaders in the trauma field to develop trauma-focused competencies to help mental health professionals build foundational trauma knowledge and skills (Bisson et al., 2010 Bisson, J. I., Tavakoly, B., Witteveen, A. B., Ajdukovic, D., Jehel, L., Johansen, V. J., … Olff, M. (2010). TENTS guidelines: Development of post-disaster psychosocial care guidelines through a delphi process. British Journal of Psychiatry, 196, 69–74. doi:10.1192/bjp.bp.109.066266; Cook, Newman, & The New Haven Trauma Competency Group, 2014 Cook, J. M., Newman, E., & The New Haven Trauma Competency Group. (2014). A consensus statement on trauma mental health: The new haven competency conference process and major findings. Psychological Trauma: Theory, Research, Practice, and Policy, 6, 300–307. doi:10.1037/a0036747; Layne et al., 2014 Layne, C. M., Strand, V., Popescu, M., Kaplow, J. B., Abramowitz, R., Stuber, M., … Pynoos, R. S. (2014). Using the core curriculum on childhood trauma to strengthen clinical knowledge in evidence-based practitioners. Journal of Clinical Child & Adolescent Psychology, 43, 286–300. doi:10.1080/15374416.2013.865192). In many countries, a wide gap exists between the need for mental health services and the availability of treatment (World Health Organization, 2011 World Health Organization. (2011). Human resources for mental health: Workforce shortages in low- and middle-income countries. Retrieved from http://whqlibdoc.who.int/publications/2011/9789241501019_eng.pdf?ua=1). This is particularly challenging for LMIC, which are home to over 80% of the global population, but utilize less than 20% of the mental health resources (Saxena, Thornicroft, Knapp, & Whiteford, 2007 Saxena, S., Thornicroft, G., Knapp, M., & Whiteford, H. (2007). Resources for mental health: Scarcity, inequity, and inefficiency. Lancet, 370, 878–879. doi:10.1016/S0140-6736(07)61239-2). Worldwide there exists a troubling cycle of disadvantage, social exclusion, and mental disorders. The consequent treatment gap is a contravention of basic human rights, as more than 75% of those identified with serious anxiety, mood, impulse control, or substance use disorders in the World Mental Health surveys in LMIC received no care at all, despite substantial role disability. Further, mental health resources are often inequitably distributed among countries, regions, and within communities. Such inequities can occur in access to care, use and outcomes of care, and by geographic region, race/ethnicity, gender, sexual orientation, and socioeconomic status (Ngui, Khasakhala, Ndetei, & Roberts, 2010 Ngui, E. M., Khasakhala, L., Ndetei, D., & Roberts, L. W. (2010). Mental disorders, health inequalities and ethics: A global perspective. International Review of Psychiatry, 22, 235–244. doi:10.3109/09540261.2010.485273). Governments must invest more of their health budgets toward these inequities in order to adequately address mental health and trauma-focused prevention and early intervention. Much attention around the world has focused on the benefits of integrating mental health care into primary care and other settings where people receive services (Ngui et al., 2010 Ngui, E. M., Khasakhala, L., Ndetei, D., & Roberts, L. W. (2010). Mental disorders, health inequalities and ethics: A global perspective. International Review of Psychiatry, 22, 235–244. doi:10.3109/09540261.2010.485273; Patel & Prince, 2010 Patel, V., & Prince, M. (2010). Global mental health: A new global health field comes of age. JAMA: Journal of the American Medical Association, 303, 1976–1977. doi:10.1001/jama.2010.616; World Health Organization, 2001 World Health Organization. (2001). Mental health: New understanding, new hope. Retrieved from http://www.who.int/whr/2001/en/whr01_en.pdf?ua=1). Such integration of physical and mental health care is especially important for trauma-exposed populations, as they often seek help in primary care rather than mental health settings (U.S. Department of Veterans Affairs, 2002 U.S. Department of Veterans Affairs. (2002). Post-traumatic stress disorder: Implications for primary care. Retrieved from http://www.publichealth.va.gov/docs/vhi/posttraumatic.pdf). While much of the global population is only seen in primary care, mental health issues (such as PTSD) often go undiagnosed in this setting (Üstün & Sartorius, 1995 Üstün, T. B., & Sartorius, N. (1995). Mental illness in general health care: An international study. West Sussex, England: Wiley and Sons.). Further, physical disease is often accompanied by psychological morbidity that is not always recognized by primary care providers (World Health Organization, 2001 World Health Organization. (2001). Mental health: New understanding, new hope. Retrieved from http://www.who.int/whr/2001/en/whr01_en.pdf?ua=1). The fact that medical comorbidities often develop with PTSD (and other psychiatric disorders) is yet another reason that primary care clinicians need training on the recognition and treatment of mental health conditions. Many efforts are underway to integrate physical and mental health and provide trauma-informed training to health care providers, including in the Department of Veterans Affairs in the U.S. and a variety of European countries. This includes a policy of routine screening by health care providers for trauma exposure and resources to assist providers in addressing trauma and PTSD in primary care (U.S. Department of Veterans Affairs, 2002 U.S. Department of Veterans Affairs. (2002). Post-traumatic stress disorder: Implications for primary care. Retrieved from http://www.publichealth.va.gov/docs/vhi/posttraumatic.pdf). Similar practices and policies are underway in other systems around the world; however, integration of mental health and trauma-informed services remains the exception and not the rule in many communities. Many suggest that a true public health approach requires mental health integration beyond primary care to include sectors such as education, justice, welfare, and labour through partnerships with government, non-governmental organizations, and the faith-based community (Collins, Insel, Chockalingam, Daar, & Maddox, 2013 Collins, P. Y., Insel, T. R., Chockalingam, A., Daar, A., & Maddox, Y. T. (2013). Grand challenges in global mental health: Integration in research, policy and practice. Plos Medicine, 10(4), e1001434. doi:10.1371/journal.pmed.1001434; Ko et al., 2008 Ko, S. J., Ford, J. D., Kassam-Adams, N., Berkowitz, S. J., Wilson, C., Wong, M., … Layne, C. M. (2008). Creating trauma-informed systems: Child welfare, education, first responders, health care, juvenile justice. Professional Psychology: Research and Practice, 39, 396–404. doi:10.1037/0735-7028.39.4.396), Stigma associated with mental health issues, such as traumatic stress, can serve as a barrier to mental health treatment and positive outcomes. According to the WHO (World Health Organization, 2010 World Health Organization. (2010). Mental health and development: Targeting people with mental health conditions as a vulnerable group. Retrieved from http://whqlibdoc.who.int/publications/2010/9789241563949_eng.pdf?ua=1), those with mental health conditions are the most marginalized and vulnerable groups in society and may face restrictions in exercising their political and civil rights. In addition, they can have difficulty accessing health care, social services, and educational and employment opportunities. Efforts to address stigma and discrimination related to mental health issues are underway. Among the strategies used include social activism, public education, and contact with persons with mental illness. A recent meta-analysis of outcome studies revealed that both education and contact had positive effects on reducing stigma for adults and adolescents with a mental illness (Corrigan, Morris, Michaels, Rafacz, & Rusch, 2012 Corrigan, P. W., Morris, S. B., Michaels, P. J., Rafacz, J. D., & Rusch, N. (2012). Challenging the public stigma of mental illness: A meta-analysis of outcome studies. Psychiatric Services, 63, 963–973. doi:10.1176/appi.ps.201100529).

4. Summary A public health framework is critical for understanding risk and protective factors for trauma and its aftermath operating at multiple levels of influence and generating opportunities for prevention at each of these levels. Primary prevention efforts should be aimed at preventing exposure to trauma itself. Secondary prevention should be directed at the prevention of trauma-related sequelae, in particular post-traumatic stress disorder. Tertiary prevention should slow the progression of trauma-related illness and disability. Advantages to adopting a public health approach to trauma include involvement of families, communities, and policymakers – making them more informed, activated, and supportive of prevention and early intervention efforts. The task is not easy, as trauma is a general term that encompasses a variety of experiences that range from rape to earthquakes. Preventive efforts will be vastly different for different traumas; thus, public health trauma advocates may need to form strategic alliances with unlikely partners, for example, highway safety officials concerned with traffic accidents, university officials concerned with sexual assaults, or government officials in areas at high risk for natural disasters. Furthermore, given the global nature of trauma, approaches may need to adapted for different cultures. Despite these challenges, there have been some modest successes in implementing mental health and trauma policies around the world. Building on these successes will help to establish a public health approach to trauma.