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Prevalence of Posttraumatic Stress Disorder(PTSD)

Prevalence of Posttraumatic Stress Disorder(PTSD)
Epidemiologic studies conducted over the past two decades provided empirical information about the prevalence of PTSD in the general population and among individuals who have been exposed to specific types of potentially traumatic events. This research indicates that most individuals who are exposed to a potential trauma do not develop PTSD.
However, this research also suggests that the likelihood of developing PTSD following traumatic stressor exposure varies with the type of trauma experienced. Additional factors that affect people’s risk of developing PTSD following traumatic stressor exposure are discussed in a subsequent section. Estimates of the lifetime prevalence of PTSD from surveys of the general adult population in the United States have ranged from 1.0% to 12.3%. The two earliest community studies of the prevalence of PTSD were carried out as part of the Epidemiologic Catchment Area (ECA) program. Using DSM-III criteria as operationalized in the Diagnostic Interview Schedule, these studies reported lifetime prevalence estimates for PTSD of 1.0% in metropolitan St. Louis and 1.3% in the Piedmont region of North Carolina. More recent surveys have found substantially higher rates of PTSD in the general population. The NCS, which also used a version of the DIS to assess PTSD, estimated a lifetime prevalence of DSM-III-R PTSD of 7.8% among persons ages 15 to 54 in the United States; the estimated current (30-day) prevalence of PTSD in the NCS was 2.8%. Using the DIS-IV, Breslau et al. estimated the conditional risk of PTSD following exposure to any traumatic stressor at 9.2% in their Detroit sample. It has been postulated that a number of factors account for variations in PTSD prevalence estimates in these and other studies, including differences in (1) diagnostic criteria, (2) the measurement approach used to ascertain exposure and assess PTSD, and (3) the demographic characteristics and representativeness of the study populations. The risk of developing PTSD following exposure to a potentially traumatic event also varies with the nature of the exposure. In the NCS, the trauma most likely to be associated with PTSD was rape; 65% of men and 45.9% of women who identified rape as their most upsetting trauma developed PTSD. In contrast, among NCS respondents who identified a natural disaster or fire as their most upsetting trauma, only 3.7% of men and 5.4% of women met lifetime diagnostic criteria for PTSD. In addition to rape, other most upsetting traumas associated with a comparatively high risk of PTSD in the NCS were combat exposure, childhood neglect, and childhood physical abuse among men (probabilities of lifetime PTSD were 38.8%, 23.9%, and 22.3%, respectively) and sexual molestation, physical attack, being threatened with a weapon, and childhood physical abuse among women (probabilities of lifetime PTSD of 26.5%, 21.3%, 32.6%, and 48.5%, respectively). Consistent with these findings, in the NWS, women who had experienced interpersonal violence (i.e., physical assault, sexual assault, or the homicide of a close friend or relative) were more than twice as likely to meet criteria for lifetime (25.8%) and current (9.4%) PTSD than women who reported noncrime stressors only. (PTSD rates in this subgroup were 9.7% lifetime and 3.4% current). Similarly, Breslau et al. found that among the men and women in their sample who reported exposure to a potential trauma, the highest conditional risk of PTSD (21.9%) was associated with the experience of assaultive violence. Epidemiologic studies of PTSD often have assessed at-risk groups of individuals who have experienced a specific type of trauma, such as veterans of armed conflicts, internally displaced persons and refugees, and victims of a range of criminal acts, including sexual assault, terrorist attacks, and torture. Although it was largely through observing the postwar experiences of soldiers engaged in combat that the syndrome known as PTSD was recognized, PTSD was not broadly or systematically studied among war veterans until the Vietnam War. Study of PTSD among Vietnam veterans was facilitated by publication of DSM-III that included PTSD as a diagnostic category defined by specific behavioral criteria. To date, the most comprehensive examination of the prevalence of PTSD among Vietnam veterans comes from the 1989 National Vietnam Veterans Readjustment Study, a congressionally mandated, community epidemiologic study of the prevalence of PTSD and other postwar psychological problems among veterans who served in the Vietnam theater of operations. Findings from the NVVRS indicated that 15.2% of men and 8.5% of women who served in Vietnam had ‘‘current’’ PTSD (i.e., met DSM-III-R criteria for PTSD during the 6 months before the study interview).
By contrast, the current PTSD prevalence among a matched (for age and race/ethnicity) sample of military veterans who did not serve in Vietnam was 2.5% among men and 1.1% among women; for nonveterans, current PTSD prevalence was 1.2% among men and 0.3% among women. The NVVRS reported lifetime PTSD prevalence rates among Vietnam veterans of 30.9% for men and 26.9% for women. Findings from other major epidemiologic studies of the prevalence of PTSD among Vietnam veterans are generally consistent with these results. Estimates of current PTSD prevalence from the majority of these studies lie within the 95% confidence interval of the NVVRS estimates (13.0–17.4%). More recent studies evaluated PTSD prevalence among military personnel who served in the Persian Gulf War (Operation Desert Shield/Storm; ODS). Estimates of current PTSD prevalence rates among ODS veterans varied across studies and ranged from 4 to 19%; however, studies generally found higher rates of PTSD among ODS veterans than among military personnel who served during the same time period but were not deployed to the Persian Gulf. During the past decade, the prevalence of PTSD associated with forms of interpersonal violence other than combat also has been evaluated. In the NCS, sexual assault (i.e., rape) was associated with comparatively high rates of PTSD, as found in other studies. Whereas sexual assaults were strongly associated with PTSD for both men and women in the NCS, only 1.8% of men who reported a physical attack as their most upsetting trauma developed PTSD, compared with 21.3% of women. Research indicates that, in general, rates of PTSD in women following physical assault are relatively high and in many cases comparable to those observed among women sexual assault survivors. Sexual victimization in childhood is also associated with PTSD in adult women. For example, in the NWS, women who were raped before age 18 were four times more likely to meet criteria for PTSD at the time of the study interview than women who were not raped as children or adolescents. McFarlane and Potts noted that the field of traumatic stress research largely evolved from the study of victims of three types of potentially traumatic events: war, interpersonal violence and related crimes, and disasters. Studies of the prevalence of PTSD among survivors of a variety of natural and technological disasters have been conducted in the United States and other countries, including several developing countries. Not surprisingly, research suggests that rates of PTSD among disaster survivors vary with the population and the type of disaster. The 1972 Buffalo Creek dam collapse and flood is one of the most widely studied natural disasters in the United States. Green and colleagues found that, as long as 14 years after this disaster, 25% of a sample of survivors followed longitudinally met criteria for a current diagnosis of PTSD. Although high, this estimate represents a decrease from the 44% current PTSD prevalence estimated 2 years after the f lood. Comparatively high rates of PTSD were also reported among survivors of other natural and technological disasters, including a tornado and an industrial accident both in the U.S., a cyclone in Fiji, and earthquakes in Armenia and Mexico.
However, other investigators reported considerably lower rates of PTSD among disaster survivors. For example, Canino, Bravo, RubioStipec, and Woodberry reported PTSD prevalence rates of approximately 5% among survivors of a mud slide and flood in Puerto Rico that killed 800 people. Similarly, Shore, Vollmer, and Tatum reported PTSD prevalence rates of 4.5% for men and 3% for women in a large sample of survivors of the Mt. St. Helens volcanic eruption. Consistent with these findings, Norris, in an epidemiological study of 1000 residents of four southeastern cities in the U.S., estimated that the rate of PTSD in disaster-exposed individuals was between 5 and 6%. The variability in PTSD prevalence rates among studies of disaster survivors suggests consideration of the dimensions of exposure (e.g., whether the individual was seriously injured or perceived a significant threat to personal safety) within classes of potentially traumatic stressors, an issue further addressed in the next section on risk factors for PTSD.

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