The importance of secondary trauma exposure for post-disaster mental disorder.

Natural disasters are a major worldwide problem. There was an average of more than 500 natural disasters worldwide per year over the last decade that either affected more than 100 people or resulted in a call for international assistance (Pielke, 2006). There were over 800 000 deaths worldwide over that same time period caused by natural disasters (Guha-Sapir et al. 2004). Financial losses in the US due to natural disasters averaged more than $50 billion a year during the decade of the 1990s and were dramatically higher in the first decade of the new millennium. The United Nations estimated that the worldwide costs of natural disasters were $109 billion in 2010, the highest annual total in recorded history (http://www.businessinsurance.com/article/20110124/NEWS01/110129973). The costs of natural disasters were even higher in 2011, however, due to the $235 billion damage caused by the Japanese earthquake and tsunami (http://www.economist.com/blogs/dailychart/2011/03/natural_disasters). The prevalence of major natural disasters has risen sharply over the past half-century (Pielke, 2006). This has been partly due to objective increases in occurrences of both weather-related events (hurricanes and tornadoes) and hydro-meteorological events (floods and earthquakes), but human factors have also been involved. The latter include population growth, migration to areas near water, environmental degradation (e.g. destruction of mangroves in coastal areas associated with population growth and changes in patterns of building and residence to meet population growth), and global warming (International Federation of Red Cross and Red Crescent Societies, 2006). The distinction between natural disasters and human-made disasters is consequently somewhat artificial. It is consequently important to note in this regard that serious risks exist of future increases in major human-made disasters, such as a pandemic linked to increases in long-distance travel and commerce. Although pandemics have occurred approximately once every 10–30 years over the last two centuries, it has been nearly four decades since the last pandemic. Increases in toxic chemical spills and accidental airplane crashes are also likely due to the financial fraying of the international transportation industry and increases in hazardous waste landfills associated with the rapid industrialization of developing countries (Krey, 2006). Research suggests that natural disasters can lead to increased population prevalence of mental illness in the range from 5% (Canino et al. 1990) to 40% (Madakasira & O’Brien, 1987); although most disasters are associated with increases in the lower half of this range (Norris et al. 1999; Cao et al. 2003; Shultz et al. 2005; van Griensven et al. 2006). While many of the mental disorders caused by such disasters are self-limiting, others persist for many years (McLaughlin et al. 2011). Interventions to address these mental health problems should be a central part of government response to natural disasters not only for humanitarian reasons but also because successful physical recovery and reconstruction depend on the psychological functioning of the affected population. A major difficulty in developing such interventions, though, is that large between-disaster variation exists in the prevalence of post-disaster mental disorders that is only weakly associated with objective disaster severity (Galea et al. 2007, 2008; McLaughlin et al. 2009). This makes it very difficult to estimate the need for mental health services for intervention planning purposes. Owing to this complexity, needs assessment surveys should be carried out to estimate magnitude of need for post-disaster mental health interventions, to target the types of interventions needed and the segments of the population most in need, and in the ideal case to monitor intervention success so as to provide a rational basis for mid-stream intervention modifications (Kessler et al. 2008). There are daunting methodological problems involved in implementing such surveys involving special problems in sampling and fieldwork (North & Norris, 2006). There are also practical challenges of integrating needs assessment survey results into intervention planning efforts. One of the implementation challenges of most interest to us involves the fact noted above that objective disaster features do not explain most post-disaster mental illness. Recent research suggests that this is true largely because secondary stressors unique to particular disaster situations often have more impact than the disasters themselves (Galea et al. 2007). For example, Wang et al. (2008) found that one of the most important challenges in treating mental disorders in the wake of Hurricane Katrina was that many low-income people with severe-persistent mental disorders lost their anti-psychotic medications along with other possessions in the flood while the pharmacies where they filled their prescriptions and their medical records were destroyed by the flood. In an effort to illustrate the difficulties involved in tracing out the extent to which the web of stressors caused by natural disasters accounts for post-disaster mental disorders, we present here data from the WHO World Mental Health (WMH) Surveys, a coordinated series of community epidemiological surveys of mental disorders carried out in a number of countries throughout the world (Kessler et al. 2009). We focus on three issues: the prevalence of exposure to natural disasters around the world; the extent to which people exposed to natural disasters also experience a range of other secondary stressors in conjunction with these disasters; and the effects of these related stressors in accounting for the overall effects of natural disasters on mental disorders.