Response to Fergusson and Boden: The psychological impact of major disasters

The comments put forward by Fergusson and Boden (2014) reflect the experience of researchers who have attempted the tough task of disentangling the different contributors to post-disaster adjustment – in these authors’ case, it has been the Christchurch earthquake. Here I will focus on a few of the points they raise.

They mention the issue of preferential sampling of disaster survivors, partly as a result of relocation but mainly because of reluctance to take part in research. This is a perennial problem for trauma researchers (and for many other mental health researchers). Our finding that those who did participate (only a disappointing 16%) were older, more likely to be female and were better educated, highlights the problem we face because each of these factors represents a risk factor for posttraumatic mental health (Ozer et al., 2003). It is interesting to juxtapose the response rate we achieved with other posttraumatic studies in different contexts. For example, Steel et al. (2009) conducted an epidemiological study of post-war mental health functioning in the Mekong Delta in Vietnam and obtained a stunning 98% response rate. It seems that the price we pay for living in a more democratic and less compliant society is that our participation rates in such studies is compromised. How we overcome this problem is a challenge. In this study, enormous effort was put into engaging with each of the communities, as well as ongoing liaison with the relevant support agencies, such as the Red Cross. Other post-disaster studies have also reported poor compliance rates; a comparable telephone study conducted 5–7 months after Hurricane Katrina had a response rate of 41.9% (Kessler et al., 2008). It is possible that a major reason our response rate was so low was that our study was conducted 3–4 years after the Black Saturday fires when people’s motivation to discuss these events had diminished. This interpretation is consistent with most studies that report marked decrease retention in longitudinal studies as time elapses.

The thorny issue of third or extraneous variables contributing to the observed outcomes is a very substantive issue. We can never be sure that we have exhaustively measured the correct predictor variables or the optimal outcomes. There are many risk factors for the onset of post-traumatic stress disorder (PTSD), as well as a myriad of moderators of adaption in the months and years after trauma exposure (Brewin, Andrews and Valentine, 2000). No single study can possibly incorporate all the potential factors that can influence outcome; however, it is important to always remember that many possible influences are not being measured and these may be pivotal to explaining specific outcomes.

Relatedly, it is important to keep in mind that our study of the Black Saturday fires was cross-sectional. By assessing mental health outcomes at 3–4 years after the fires, we essentially took a ‘snapshot’ of adaptation. In recent years the field has realized that people’s responses following trauma fluctuate greatly over time; one study of traumatically injured patients across Australia showed that whereas the incidence of PTSD remained stable over multiple assessments in the 2 years after injury, half the patients altered their diagnostic status at each assessment (Bryant et al., 2013). This problem is addressed to a degree by longitudinal designs that assess people on three or four occasions, which allows latent growth mixture modeling to map distinct trajectories that people follow across time. Multiple studies converge on documenting four distinct trajectories: (1) chronically distressed, (2) initial distress followed by recovery, (3) delayed or worsening symptoms, and (4) consistently resilient or resistant pattern that is characterized by ongoing stable mental health (Bonanno et al., 2012, Pietrzak et al., 2013). We are conducting ongoing follow-ups of the participants in our study, with the hope that we can map the longer-term trajectories of people as they manage both the after-effects of the fires and also the ongoing challenges of future weather events and difficulties facing regional districts of Australia.

Understanding how people cope in the long-term after disasters is critical. Considering the increasing impact of climate change on our environment, including extreme weather events that will include damaging episodes, we must comprehend the consequences so adequate planning can be implemented. To date the emphasis has been on the acute and intermediate effects, but it is just as important to understand the longer-term ripple effects of disasters upon individuals and communities. These more subtle effects can impact psychological functioning, social and family cohesion, community structures and economies. Further, many disasters affect communities in the context of ongoing stressors, such as drought or economic downturn, which compound the longer-term effects. In this sense, we need to see the role of traumatic events in the context of broader environmental challenges rather than a discrete event that happens in isolation. By adopting a more comprehensive and longer-term view of the effects on mental health, more targeted prevention and intervention programs may facilitate the longer-term adaptation of those affected by these extreme events.