PTSD: National Center for PTSD
The Impact of Disaster and Mass Violence Events on Mental Health
The Impact of Disaster and Mass Violence Events on Mental Health
In the aftermath disaster and mass violence, almost everyone who experienced the event will have stress reactions. For most people, these reactions will gradually decrease over time, but some survivors and responders—especially those with specific risk factors—may experience longer-term or severe responses.
Those affected by disaster and mass violence exhibit a wide variety of psychological, behavioral, physical, and emotional reactions. The most common mental health diagnoses reported in research samples are posttraumatic stress disorder (PTSD), depression, anxiety, acute stress disorder, and complicated grief. Negative affect, perceived stress, physical health problems/somatic concerns, and poor sleep quality are also reported in disaster research (1-8). These reactions may be relatively common in the 6-12-month period after a disaster (9), and have been shown across a range of events.
Scale of Mental Health Reactions
The impact of disasters and mass violence on the mental health of survivors can vary. The proportion of survivors who develop chronic long-term problems is generally less than 10%, and rarely exceeds 30% (6-8). Two comprehensive reviews of disaster research document the magnitude of effects for 225 samples of survivors of 132 distinct events (4,5). Moderate effects—increased or prolonged stress, but little enduring psychopathology—were present in 50% of the samples. For 24% and 17% of the samples, respectively, the effects were severe or very severe. Severe effects were defined as a high (25% to 49%) prevalence of clinically-significant distress, while prevalence of clinically-significant distress of 50% or higher was indicative of very severe post-event effects.
Time Frame for Reactions
Research shows that a significant proportion of those exposed to disaster or mass violence will experience immediate intense reactions, which decline over time (e.g. 10-12). Acute distress reactions within the first few weeks should not necessarily be regarded as pathological. Most affected individuals are likely to simply need support and provision of resources in the early phases post-event, rather than traditional diagnosis and clinical treatment. Therefore, screening and identification of those who may need services requires some sensitivity.
In longitudinal disaster studies, stress reactions and symptoms are most likely to be apparent in the year following the disaster, with the majority of those studied showing improvement with time (4). For instance, an analysis of longitudinal studies of two devastating events—a widespread flood in Mexico and the 9/11 terrorist attacks in New York—found seven distinct trajectories of post-event functioning. Up to 50% of survivors showed resistance, never exhibiting more than three PTSD symptoms. About 10% to 32% showed resilience; they had mild symptoms that improved rapidly. Much smaller percentages had severe symptoms that were maintained or that increased over time (10). In another 10-year study of a major fireworks disaster, around 4% to 6% of affected individuals suffered from severe persistent PTSD symptomatology, depression, anxiety and sleep problems. Ten years after the disaster, 16.7% had severe PTSD symptoms (13).
Survivors with high exposure to the event, who lack of social support, or experience ongoing adversity are more likely to face enduring post-disaster distress and symptomatology (10, 11, 14-19). This is true for both adults and children.
A wide variety of mental health reactions have been reported in studies with survivors of disaster and mass violence. The scale of impact varies across events, with the majority of studies reporting moderate effects that fade over time. However, those most strongly exposed—as well as those who face ongoing adversities—are at risk for long-term problems, even up to 10 years after the event.
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