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The Effects of Natural Disasters

A National Center for PTSD Fact Sheet
Prepared by: Fran H. Norris, Ph.D.

The psychosocial consequences of natural disasters have been studied extensively. When Norris and colleagues (2002) reviewed this literature, they found a wide range of effects. About a third of these studies found effects that were quite severe, meaning that a high percentage of study participants exhibited clinically significant distress or diagnosable disorders. The most frequently reported condition was PTSD, followed by depression, and then other anxiety disorders. Many survivors also reported nonspecific distress, health problems, chronic problems in living, and resource loss. Within the adult samples, risk factors for adverse outcomes included more severe exposure, female gender, middle age, ethnic minority group membership, secondary stress, prior psychiatric problems, and weak or deteriorating psychosocial resources. Consistent support has been found for the importance of coping self-efficacy in predicting psychological outcomes from a variety of disasters, including but not limited to hurricanes (Benight & Bandura, 2004).

In some of these studies, participants were interviewed more than once so that the disaster's effects could be studied over time. Most often, people improved as time passed. However, almost all studies included a minority of participants who did not improve but, for whatever reason, continued to be distressed or impaired long after the event. As the authors of these studies often remarked, these particular people who do not recover on their own are especially important to understand and serve.

Quite a few studies have been conducted specifically on the effects of hurricanes, including such major events as Hurricane Hugo, Hurricane Andrew, and Hurricane Mitch. Norris and colleagues (2002) described Hurricane Andrew as a good example of a "high impact disaster." In one study of 400 highly exposed residents of southern Dade County, 25% of the sample met study criteria for PTSD 6 months after the hurricane. Symptoms of depression and avoidance remained high as late as 30 months after the hurricane struck (Norris et al., 1999). Lasting symptoms were especially likely when people experienced other forms of life stress in addition to the hurricane or had poor self-esteem or weak social ties. Long after Hurricane Andrew, many people felt less positive about the quality of their social relationships than they had felt before the disaster (Norris & Kaniasty, 1996), suggesting that perceptions of social support are also harmed by disaster experience.

In this study, the effects of Hurricane Andrew appeared to be more severe for Latinos, especially less acculturated Latinos, than for non-Hispanic Whites and Blacks (Perilla and colleagues, 2002). To a degree, this finding was explained by Latinos' greater exposure, but it was also partially explained by Latinos' higher levels of fatalism (external control) and acculturative stress (discomfort in dealing with members of other ethnic groups). The mediating role of fatalism is consistent with a large literature showing that low perceived control is a risk factor for poor psychological outcomes. Acculturative stress might have hindered help-seeking or exacerbated the effects of other stressors.

Altogether, the evidence from this study of Hurricane Andrew, as well as from other disaster studies, suggests that the long-term emotional consequences of disaster follow strongly from survivors' thoughts or beliefs. Adults at risk for mental health problems think that they (a) are uncared for by others, (b) have little control over what happens to them, or (c) lack the capacity to manage stress.

These hurricane-specific findings are consistent with findings from research on other forms of trauma that have examined the factors predicting whether or not a person develops chronic PTSD. Two of the strongest factors influencing recovery are subsequent life stress and social support from others. The most recent research with survivors of assaults and motor vehicle accidents has consistently shown that the presence of negative social support impedes recovery (Dunmore, Clark, & Ehlers, 2001; Ullman & Filipas, 2001; Zoellner, Foa, & Brigidi, 1999). Family members' critical comments about the length of time taken for recovery seem to stand in the way of trauma victims' recovery in treatment for PTSD.

Related Web Resources

Range, Magnitude, and Duration of the Effects of Disasters on Mental Health: Review Update 2005
by Fran H. Norris Dartmouth Medical School and National Center for PTSD

More detailed information on the mental health impact of disasters is found in this article which is posted on the Research Education in Disaster Mental Health (REDMH) Web site.

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