Risk Factors and Hypothesis for Posttraumatic Stress Disorder (PTSD) in Post Disaster Survivors

Disasters, both natural and man-made, affect millions of people around the world every year. Natural disasters (e.g., earthquakes and hurricanes) and man-made disasters (e.g., traffic accidents, acts of terrorism and wars) can cause mental trauma with long-lasting consequences (Chou et al., 2005; Chou et al., 2007). The impact of a mass disaster or man-made trauma on the individual is a composite of two major elements: the catastrophic event itself and the vulnerability of those people affected by the event. To this end, post-disaster survivors need specific, systemic evaluation and management (Sapir, 1993).


Introduction
Disasters, both natural and man-made, affect millions of people around the world every year. Natural disasters (e.g., earthquakes and hurricanes) and man-made disasters (e.g., traffic accidents, acts of terrorism and wars) can cause mental trauma with long-lasting consequences (Chou et al., 2005;Chou et al., 2007). The impact of a mass disaster or man-made trauma on the individual is a composite of two major elements: the catastrophic event itself and the vulnerability of those people affected by the event. To this end, post-disaster survivors need specific, systemic evaluation and management (Sapir, 1993). Breslau et al. (1991) estimated that 6% to 7% of the US population is exposed to disaster or trauma every year, while Wang et al. (2000) showed that natural disasters affect an average of approximately 200 million people in China every year, several thousand of whom do not survive. In the aftermath of these catastrophic events, PTSD is one of the most common psychiatric diseases suffered by post-disaster survivors. The prevalence of PTSD ranged from 3.0% to 34.3% in Taiwan after the 1999 earthquake (Chou et al., 2004a,b), it was approximately 25% in Turkey after the 1999 earthquake (Tural et al., 2004), and it was reported as 74% in Armenia after the 1988 earthquake (Armen, 1993).

The relationship between disasters and Posttraumatic Stress Disorder (PTSD)
In a systemic review of the literature, Andrews, Brewin, Philpott, & Stewart (2007) found that delayed-onset PTSD in the absence of any prior symptoms was rare, whereas delayed onset that represented exacerbations or reactivations of prior symptoms accounted for, on average, 38.2% and 15.3% of military and civilian cases of PTSD, respectively. Generally, the lifetime and current prevalence rates for psychiatric disorders range anywhere from 1% to 74% (Breslau, Davis, Andreski, & Peterson, 1991;Carr et al., 1995;Chang et al., 2003;Chou et al., 2003;Tainaka et al., 1998), with women twice as likely as men to be affected. Furthermore, women report more symptoms of anxiety and depression than men (Chou et al., 2003;Chang et al., 2003).

PTSD with psychiatric co-morbidity
The majority of the research (Goenjian et al., 2000;Green, Lindy, Grace, & Leonard, 1992;Maj et al., 1989;McFarlane & Papay, 1992;Rubonis & Bickman, 1991) provides evidence of psychological sequelae that includes PTSD, major depressive episodes, sleep disorder, anxiety, and substance abuse after disasters. Furthermore, major depressive episodes and PTSD are the most common disaster-related psychiatric diagnoses and are strongly associated with one another (McFarlane & Papay, 1992;Goenjian et al., 2000;Green et al., 1992). Individuals confronted with disasters or major stressors exhibit greater psychological impairment and are more vulnerable to psychiatric diseases (Chou et al., 2005). The incidence of PTSD is higher than that of other major depressive episodes in the majority of the studies (Bromet & Dew, 1995;Chou et al., 2003;Chou et al., 2004a;Chou et al., 2004b;Chou et al., 2005;Davidson et al., 1991;Davidson 1995;Goenjian et al., 1994;Green et al., 1992;Sharan et al., 1996). In contrast to natural disasters, however, higher co-morbidity has been found with combat-related PTSD. Such co-morbidity includes drug and alcohol abuse, antisocial personality disorder, somatization disorder, and depression, and it is particularly prevalent when determined from an historical perspective (Green et al., 1992). PTSD can be triggered by a variety of traumatic events and is strongly associated with all other examined mental disorders (Brady, Killeen, Brewerton, & Lucerini, 2000;Goenjian et al., 2000;Perkonigg, Kessler, Storz, Wittchen, 2000). For example, the combination of PTSD and panic and phobic disorders is an important predictor for PTSD chronicity (McFarlane & Papay, 1992;Ursano, Kao, & Fullerton, 1992). Furthermore, the rate of psychopathology is higher in post-disaster groups than in either the same groups prior to trauma or in control groups (Maj et al., 1989;Rubonis & Bickman, 1991).

Psychiatric studies of post-Chi-Chi earthquake survivors
Researchers focusing on survivors of the Chi-Chi earthquake in Taiwan (Su, Chou, Lin, Tsai, 2010) have found evidence of psychological sequelae that includes posttraumatic stress disorder (PTSD), major depressive disorder, sleep disorder, anxiety, and substance abuse (Chou et al., 2004a(Chou et al., , 2004b(Chou et al., , 2005Chen et al., 2001;Chang et al., 2002;Lai et al., 2004;Hsu et al., 2002;Kuo et al., 2003;Liu et al., 2006;Tsai et al., 2007;Wu et al., 2006;Yang et al., 2003). The quality of life for survivors of traumatic events who develop psychiatric illnesses or impairments is worse than that for survivors without any psychiatric illness (Chou et al., 2004b;Tsai et al., 2007;Wu et al., 2006). In addition, rescue workers such as nurses, fire fighters, and soldiers may develop physical or mental impairments (Chang et al., 2008;Liao et al., 2002;Shih et al., 2002;Yeh et al., 2002). We used PubMed to identify Chi-Chi earthquake-related papers published through June of 2009. All of the Chi-Chi earthquake papers related to psychiatry are summarized in Table 1 (cited from Su, Chou, Lin, Tsai, 2011).

The risk factors of PTSD
Researchers who study risk factors for PTSD have identified aspects of demographic data, psychological factors, psychiatric symptoms, and post-trauma social resource factors as important factors that contribute to the development of the disease.

Demographic data
Some researchers who have examined gender differences suggest that females are more likely than males to develop PSTD (Chou et al., 2005;Helzer, Robins, & McEvoy, 1987;Johnson & Thompson, 2008;Lazaratou et al., 2008). A possible explanation for this is the specific reactions that result from feminine characteristics to a traumatic event . Additionally, there are previous studies that have associated old age with an increased risk of developing PTSD (Goenjian et al., 1994;Lewin, Carr, Webster, 1998). However, a recent study has suggested contradictory results (Lazaratou et al., 2008).

Biological factors
Neuroendocrine data provide evidence of insufficient glucocorticoid signaling in stressrelated neuropsychiatric disorders, while Nutt (2000) has suggested that individuals develop PTSD due to neuroendocrine dysregulation. Furthermore, impaired feedback regulation of relevant stress responses, especially immune activation/inflammation, may, in turn, contribute to stress-related pathology that includes alterations in behavior, insulin sensitivity, bone metabolism, and acquired immune responses (Raison & Miller, 2003). Because the hypothalamic-pituitary gland-adrenal axis (HPA) regulates hormone reactions during stress, PTSD severity seems to decrease when individuals exposed to traumatic   Thabet & Vostanis, (2000) and Gurvits et al. (1997) found more positive soft neurological signs in PTSD participants than in participants who experienced similar trauma but did not develop PTSD. Many trauma victims complain of memory impairment, such as difficulty remembering daily activities, frequent compulsive recall of the traumatic event in detail, memory gaps, island-like memory, difficulties with declarative memory, and intrusive memories. Anderson et al. (2004) used functional magnetic resonance imaging (MRI) to identify the neural systems involved in keeping unwanted memories out of one's awareness. Controlling unwanted memories is associated with increased dorsolateral prefrontal activation (DLPF), reduced hippocampal activation, and impaired retention of those memories. Both prefrontal cortical and right hippocampal activations predicted the magnitude of forgetting. These results confirm the existence of an active forgetting process and establish a neurobiological model for guiding inquiry into motivated forgetting. There are still gaps in our understanding of the genetic underpinnings of PTSD. For example, while Stein et al. (2002) have found moderate hereditary factors in individuals with PTSD symptoms, no single gene that causes PTSD has been identified. Meyer et al. (1999) indicated that some psychiatric symptoms and disorders are risk factors for PTSD (Meyer, Taiminen, Vuori, Aijälä, Helenius, 1999). For example, certain personality traits, such as neuroticism and introversion, are associated with an increased risk of PTSD (Lewin, Carr, & Webster, 1998;McFarlane, 1988) while some studies indicate that certain psychiatric disorders may be predictive of chronic PTSD (Engdahl, Dikel, Eberly, & Blank, 1998;McFarlane & Papay, 1992). Then again, other studies have examined the long-term course of PTSD. A longitudinal analysis of the mental health of school children after the great Hanshin Awaji earthquakes indicated that some survivors' psychological reactions emerged early and disappeared early (i.e., within two years after the disaster); however, this is contrary to findings from other studies . Lazaratou et al. (2008) have found that greater numbers of PTSD symptoms emerged during the first 6 months after the earthquake and were associated with a greater impact on the victims' lives 50 years after the event. Uemoto et al. (2000) posited that the best predictor of recovery from chronic PTSD was the initial level of post-traumatic reaction immediately after the accident. However, few data are available on the long-term effects caused by a disaster .

Post-trauma social resource factors
Inadequate social support after the trauma adds to the risk of developing PTSD (Chou et al., 2004a;Wang et al., 2000). Not surprisingly, higher levels of post-disaster life events are also related to the risk of developing PTSD (Chang, Connor, Lai, Lee, & Davidson, 2005). Similarly, social stressors such as economic or marital issues or a disruption of one's daily life, including relocation, the death of an intimate partner, or other significant loss problems are associated with a greater risk for developing PTSD.

Hypothesis for PTSD
Hobfoll's conservation of resources (COR) model has been well supported by previous studies on natural disasters (Sumer, Karanci, Berument, & Gunes, 2005). According to www.intechopen.com Hobfoll's conservation of resources stress theory (Hobfoll, 1989;Chou et al., 2007), resource loss is an important determinant of individual stress and physical and mental health, including PTSD. Brewin et al. (2000) also found that the effect sizes of all risk factors were modest. Factors operating during or after the trauma (e.g., trauma severity, lack of social support, and additional life stress), however, had somewhat stronger effects than did pretrauma factors. Consequently, multiple risk factors constitute a network that results in psychiatric illness. According to Hobfoll's conservation of resources theory, resource loss is an important determinant of individual stress and physical and mental health, including PTSD. Our hypothesis states that an individual reaches a sub-threshold of psychiatric illness and then develops the illness due to a decreasing availability of resources, an accumulation of risk factors, and/or a major stressful event. Furthermore, unresolved, sub-clinical psychiatric symptoms caused by a disaster or major life event may increase a survivor's sensitivity to future stresses. When faced with stress, frustration (e.g., life events), or traumatic events (e.g., brain damage or deprivation of internal or external resources) individuals, either suddenly or gradually, become more vulnerable to psychiatric impairment and diseases such as PTSD. An individual might reach a sub-threshold of PTSD and then develop the illness due to a decreased availability of resources, an accumulation of risk factors (personality traits, poor social interactions, etc.) or a major stressful event. Furthermore, unresolved, subclinical psychiatric symptoms caused by a disaster may increase a survivor's sensitivity to future stresses. Other factors that tend to increase an individual's vulnerability to psychiatric problems include brain damage, heredity, personality traits, life events, and social interactions.

The treatment and rehabilitation of PTSD
Treatment or rehabilitation efforts should concentrate not only on severe psychiatric symptoms, emotional disturbances and personality traits or disorders, but also on interpersonal and social-environmental interactions. To treat PTSD, clinicians only use drugs and do not provide psychosocial treatment; thus, they cannot meet the true needs of the survivor. Based on the bio-psychosocial causation model of psychiatric disease as it applies to public health, we propose a model of the causation of PTSD. Issues related to PTSD that are most in need of further study include biological causation, psychosocial recovery, and long-term evaluation of psychological rehabilitation.

Conclusion
Although changes in emotional, cognitive, behavioral, and biologic states are transitory for most individuals after a catastrophe or major trauma, psychological trauma may persist much longer in some victims. While the psychological profiles of these victims are often altered, given their vivid and repetitive recollection of the traumatic events (Chou et al., 2004b;Chou et al., 2005;Lin et al., 2002), Wang et al. (2000) determined that prompt and effective post-disaster intervention might mitigate the impact of initial exposure and reduce the probability of PTSD occurrence. Issues related to PTSD most in need of further study include biological causation, psychosocial recovery, and long-term evaluation of psychological rehabilitation.