THE ADVERSE EFFECTS of large-scale disasters on the health of affected adults are well documented,[1-3] showing that victims may suffer from a wide range of health disturbances in especially the short term, but also in the middle and long term. These include, but are not limited to, symptoms of anxiety and depression, sleeping problems, re-experiencing of the event, somatic problems, and bereavement. In general, a minority will develop a mental disorder, such as the most-often examined post-traumatic stress disorder (PTSD). On a population level, the prevalences of post-disaster health problems decrease as time passes. The exact course will be dependent on for instance the nature of the disaster, the affected population, disaster recovery response, and provided support and care. Individual patterns of post-disaster health disturbances, however, do not necessarily reflect this general course and may vary. More recent studies suggest that this variability can be captured by approximately six prototypical trajectories such as resilience; recovery; delayed (chronic) dysfunction; resistance; relapsing/remitting; and chronic dysfunction.[5-8]
Of special interest and importance is the presence of the chronic dysfunction trajectory, which encompasses all affected adults who do not recover from initial severe symptoms during a substantial period of time. Longitudinal multi-wave studies (three or more waves) over a longer period starting soon after the disaster, are best suited to provide insight into this trajectory.[9-11] Retrospectively collected data on lifetime severe (chronic) symptoms since the event, are sensitive to recall bias. A relatively small number of studies included multi-wave assessments over a few years, allowing an evaluation of this chronic trajectory. In addition, they mainly focused on PTSD (symptomatology).[6-8, 12] Exceptions are one five-wave study 6–39 months after the event that assessed persistent heavy alcohol use, and one two-wave study 3–4 years and 5–6 years after the event that examined asthma, depression and PTSD, after the 9/11 terrorists attacks.
Longitudinal multiwave studies starting a few days or weeks after the disaster covering a substantial post-disaster period of ≥10 years are, however, to the best of our knowledge, absent. Moreover, there is a serious lack of long term disaster-studies.[1, 2, 4] Therefore, the prevalences of persistent mental health disturbances in the long term and the proportion (ratio) of affected adults with initial severe symptoms who develop severe persistent symptoms are unknown.
To fill this gap of knowledge, the aim of the present four-wave longitudinal study was to examine the development of persistent health disturbances in the period from 2–3 weeks to 10 years after a disaster. Data were analyzed from surveys after a major fireworks disaster in the Netherlands (13 May 2000): a devastating explosion in a fireworks storage facility located in a residential area in the city of Enschede, the Netherlands. This disaster severely damaged or destroyed approximately 500 houses, killed 23 people and injured >900 victims.
We focused on the following mental health disturbances: severe PTSD symptoms; anxiety and depression symptoms; sleeping problems; and use of physician-prescribed tranquilizers. To assess whether symptoms and use were more prevalent than normal, we also assessed chronic symptoms and use of tranquilizers in a comparable non-affected group that participated in two waves. In addition, we assessed to what extent persistent symptoms can be explained by the level of disaster experience or exposure.
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- Appendix: Appendix I. Response of affected Dutch Native residents
- Appendix: Appendix II. Demographics, disaster experiences and symptoms
The main outcomes are that a small but significant group of adult AR suffered from severe persistent PTSD symptomatology (6.7%) and depression symptoms (6.2%), and to a somewhat lesser extent from persistent anxiety (3.8%) and sleeping problems (4.8%) during the 10 years after a disaster. Among those with severe symptoms 2–3 weeks after the disaster, approximately one out of 10 developed persistent symptoms up to 10 years after the event. Use of tranquilizers increased after the first wave, and approximately one out of five reported using tranquilizers at all four waves.
The ratio of persistent divided by initial prevalence estimates is important because it further enables comparisons across study outcomes. The reason is that prevalences of post-disaster health problems at particular moments or periods after disasters are partly dependent on who were considered potential victims (or were asked to participate), that is, the denominator, in calculating prevalence estimates (which may partly explain differences in estimates between studies). In a similar way, this denominator affects prevalence estimates of chronic or persistent mental health disturbances. By calculating the ratio, this denominator is eliminated, facilitating comparisons between different studies. For instance, compared to the four-wave study 6–42 months after 9/11, the prevalence of severe chronic PTSD symptoms in the present sample in a comparable period (T1–T3) was much higher: 16% versus 2% (based on PTSD symptoms in the past 6 months/since previous wave), but the prevalence of these symptoms among those with severe PTSD symptoms in the first wave in the present sample appears to be smaller: 23% (16.7/70) versus 35% (2.0/5.8), respectively (S. Galea, pers. comm., 2010). A three-wave study after an earthquake in Turkey, with assessments from 1–3 to 8–20 months after the event, reported less (5.2%) chronic PTSD than the chronic PTSD symptoms (33%) in the present sample during the first 18 months. The ratio of persistent/initial symptoms was also much lower: 17.2% (5.2/30.2) versus 47.1% (33/70) in the current study. Following the Newcastle earthquake in Australia, a four-wave study 27–144 weeks after the disaster found that 14.4% had persistent PTSD (based on IES cut-off >25), while 33.2% reported severe PTSD symptoms during the first year (ratio 43.4%). Due to the absence of other multiwave long-term disaster studies with early assessments, we cannot compare the present long-term outcomes (prevalences of persistent symptoms and computed ratios).
Compared to non-affected residents, chronic anxiety symptoms and sleeping problems appeared to be more prevalent in the long term. No other studies with similar endpoints (i.e. up to 10 years after the disaster) are available with which to compare the results. Ten years after the disaster, 16.7% (95%CI: 14.2–19.1%) had severe PTSD symptoms. Higher prevalences of PTSD symptomatology were found 10 years after an oil platform disaster (PTSD diagnosis, 21%), and 14 years after the Buffalo Creek disaster (PTSD diagnosis, 25%). In line with the literature, the prevalence of late-onset severe chronic PTSD symptoms was very low (1.8%).
After adjustment for age and gender, a high disaster exposure significantly predicted persistent symptoms during 10 years after the disaster. Although there are no long-term multiwave studies with which to compare the present findings, this outcome suggests that high disaster exposure may help in the early identification of those at risk for persistent severe anxiety and depression symptoms, sleeping problems and especially PTSD (adjusted OR, 3.43, 2.95, 3.74 and 4.20, respectively).
The strengths of the present study are the large sample size, four-wave study design, use of well-validated instruments and controls, but some limitations and the context of the present study need to be discussed. First, participants were adult Dutch native residents. The present findings may not be applicable to ethnic minorities. Results are based on well-validated and often used questionnaires (SCL-R-90 and IES) but not on clinical or diagnostic interviews. Although we used sophisticated statistical techniques (multiple imputation) to target the problem of missing values across the four surveys, it should be noted that the response at the fourth wave was relatively low (61%). In addition, we did not examine pre-disaster history of psychiatric illness and family history of psychopathology, which may influence persistent post-traumatic stress symptoms.[2, 3]
Second, the question remains as to which time intervals between waves should be chosen. Here, time intervals differed from 18 months to approximately 6 years. Therefore it is possible that at some moment(s) between the surveys some of the participants, as in other multiwave studies, did not suffer from severe symptoms, or did not use tranquilizers (or vice versa). To our knowledge, to date there is no general consensus on which time intervals in multiwave disaster studies are preferable. In theory, multiple repeated mental health measurements, that is, for instance every 1–3 months throughout the years, may help to solve this problem. Nevertheless, this solution may introduce new complex problems (such as the heavy burden for participants and negative influence on response rates) that presumably will counteract the advantages.
Third, after the disaster a special after-care unit offering mental health services (MHS) for AR was opened. Previous studies based on the first three waves demonstrated that among those with ongoing symptoms a large majority used MHS, which may have affected outcomes. This possible effect, however, may also have take place in other disaster studies.[6, 26] Disaster research, especially in Western countries, has shown that at different time points after disasters in general a variable minority with current PTSD (symptomatology) use MHS.[6, 27] Some disaster studies explicitly mention that respondents with severe mental health disturbances during assessment were directly referred to or offered treatment.[28, 29]
Nevertheless, in line with other long-term disaster studies, results indicate that attention to the long-term effects of disasters on mental health is required. For instance, general practitioners (in several countries a patient's main doctor) should be aware that some of the disaster victims will suffer from persistent symptoms in the long term. Because this last group appears to be relatively small, there is a chance that, especially after 10 years, general practitioners simply forget to assess to what extent persistent symptoms are a result of the disaster 10 years earlier.