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The diagnosis of post-traumatic stress disorder (PTSD) has been the focus of considerable attention since it first appeared in the diagnostic nomenclature in 1980. Since that time, the diagnostic criteria have been refined, with both DSM-5 (American Psychiatric Association, 2013) and ICD-10 (World Health Organization, 1993) recognizing the condition. In recent years, a major focus of research and debate has been the impact of gender on the risk of developing PTSD and related conditions following traumatic exposure. In general, the available evidence suggests that there is a two-fold risk of PTSD among women compared with men (Tolin & Foa, 2006); there has been considerable interest in developing theories and models to explain this gender difference (Christiansen & Elklit, 2013; Olff, Langeland, Draijer, & Gersons, 2007). The purpose of this chapter is to provide an overview of key issues regarding PTSD in women.
The nature of PTSD
According to DSM-5 (American Psychiatric Association, 2013), the first criterion to be met for a diagnosis of PTSD is the experience of a traumatic event (criterion A), defined as involving actual or threatened physical threat to the self or others. Four broad clusters of symptoms characterize the disorder and are required in some form for a diagnosis. First, evidence of reexperiencing the trauma is required (known as the B criteria). This is likely to take the form of intrusive memories, images or perceptions that invade consciousness; dreams; flashbacks; and emotional distress or physical reactions on reminders of the traumatic event. These symptoms are very distressing and the next symptom group (C criteria) is often conceptualized as a way of trying to prevent their return. The C criteria include evidence of active avoidance, often with a phobic quality (such as attempts to avoid people, places, situations, thoughts, feelings and conversations associated with the trauma). The D criteria include alterations in mood or cognitions, sometimes thought of as “passive avoidance,” with characteristic symptoms of social withdrawal; loss of interest; persistent negative emotions or inability to experience positive emotions; distorted beliefs about the cause or consequences of the event; exaggerated negative beliefs about oneself or the world; and psychogenic amnesia. The E criteria are those of persistent hyperarousal, characterized by sleep disturbance; anger and irritability; poor concentration; hypervigilance; exaggerated startle response; and reckless or self-destructive behavior. The symptoms must have been present for at least 1 month before a diagnosis of PTSD can be made, and must be associated with significant distress and/or impairment of social or occupational functioning.
Many symptoms of PTSD overlap with those of other diagnoses. There is also ample evidence that PTSD is often comorbid with a range of other Axis I and Axis II (personality) disorders (Chapman et al., 2012; Kessler et al., 1995; Pietrzak et al., 2011). Thus, the clinical presentation in both women and men is often quite complex. In more chronic cases, the disorder is associated with progressively deteriorating social and occupational functioning, often confronting the clinician with a myriad of psychosocial problems in addition to the primary symptom set.
Prevalence of PTSD
Epidemiological studies from several countries have indicated that, while women are less likely than men to be exposed to traumatic events, the prevalence of PTSD within the community is significantly higher among women (Breslau et al., 1998; Chapman et al., 2012; de Vries & Olff, 2009; Kessler et al., 1995; Norris et al., 2003; Pietrzak et al., 2011; Stein et al., 1997). One of the most influential of those studies, the National Comorbidity Study (NCS), estimated that the lifetime prevalence of trauma exposure was 51% for women and 61% for men; however, lifetime rates of PTSD were estimated at 10% for women and 5% for men (Kessler et al., 1995).
In Norway, Amstadter and colleagues (2013) found that the lifetime rate of trauma exposure was 23% for women and 32% for men, whilst the rate of lifetime PTSD was roughly 4 times higher among women compared with men (15% versus 4%). Similarly, a national survey of Australian adults found that although an equal proportion of women and men reported trauma exposure (76% and 74% respectively) (Mills et al., 2011), the 12-month prevalence of PTSD was significantly greater in women than men (9.7% versus 4.7%) (Chapman et al., 2012).
Environmental and cultural factors
It is worth noting that the prevalence of PTSD generally, as well as the differential rates of PTSD in women and men, may vary according to environmental and cultural factors. In a comparative study across four post-conflict, low-income countries, de Jong and colleagues found equal rates of PTSD in women and men in Ethiopia, higher rates among women in Algeria and Cambodia, and higher rates among men in Gaza (de Jong et al., 2001). In some settings, it is possible that gender differences may be obscured by the disproportionately high rates of post-traumatic symptomatology that characterize populations exposed to extreme prolonged trauma (Atwoli et al., 2013; Norris et al., 2002). For example, elevated rates of PTSD, depression and anxiety were reported for Armenian communities exposed to either extreme earthquake trauma or severe political violence 4 years later, regardless of gender or trauma type (Goenjian et al., 2000).
There is some evidence that the gender difference in the prevalence of PTSD may be particularly evident in cultural groups that emphasize traditional gender roles. Norris and colleagues (2001) compared gender differences in the rate of PTSD in Mexican, African-American and Anglo-American samples following hurricanes in Mexico and the United States and found that the gender difference was greatest in the Mexican sample and least in the African-American sample, with the Anglo-American sample falling in between. The authors suggested that these rates may reflect differences in gender roles in Mexico and the United States; the discouragement of emotional expression in Mexican men may exacerbate gender differences in the diagnosis of PTSD and related disorders, whilst these differences may be reduced in African-American communities, which are considered to have a more egalitarian approach to gender role expectations.
In a similar vein, the process of socialization in different cultures may produce gender differences in coping style, which may mediate response to stressful life events. Gavranidou and colleagues (2003) have suggested that, as a result of cultural expectations, women are more likely to practice emotion-focused coping whereas men are more likely to use problem-focused coping, with the latter often associated with better outcome. Similarly, Foster and colleagues (2004) suggested that gender differences in PTSD may reflect socialization processes, whereby women are taught to internalize and men to externalize negative emotions in accordance with accepted feminine and masculine roles (see also Chapter 1). Thus, women and men may respond differently to trauma, with women more likely to internalize emotions in the form of anxiety and depression, and men more likely to externalize in the form of aggression and substance use. If this is the case, then a tendency to internalize may result in higher rates of PTSD diagnoses in women.
Developmental context
While relatively few epidemiological studies have considered trauma exposure and response across the life span, preliminary evidence suggests that gender differences may manifest from a relatively early age. Similar to adult studies, a number of epidemiological studies of adolescents have found an elevated risk for PTSD among females compared with males (Giaconia et al., 1995; Landolt et al., 2013; McLaughlin et al., 2013). Landolt and colleagues (2013) did not find gender differences in rates of exposure to any traumatic event among Swiss adolescents, but did find that female gender, not living with both biological parents, lower parental education and exposure to multiple traumatic events were significant risk factors for PTSD. In the United States, McLaughlin and colleagues (2013) found that adolescent females were more likely to develop PTSD than males, even after controlling for type of trauma exposure. In addition, and consistent with the extant literature (Brewin et al., 2000; Ozer et al., 2003), the results indicated that prior trauma exposure was associated with increased vulnerability to PTSD among adolescents regardless of gender.
Exposure to traumatizing events at an early developmental stage potentially has serious implications for the way in which individuals deal with stress and trauma in later life, and this may be particularly true for females. Breslau and colleagues (1997) found some evidence of differential traumatic stress reactions among women and men depending on the timing of the trauma, with gender differences in the rate of PTSD more marked if first exposure to trauma occurred at or before age 15. While women remained at higher risk following first exposure that occurred later, the gender difference was less pronounced, suggesting that women’s greater vulnerability to PTSD may be greater if exposure occurs during childhood.
Although beyond the scope of this chapter, it is important to note that the long-term effects of prolonged exposure to childhood trauma may not be best conceptualized as PTSD. The contribution of prolonged and severe developmental trauma to the development of Axis II personality disorders, especially the B cluster such as borderline and antisocial personality disorder, has been the subject of considerable debate in the literature (e.g., McLean & Gallop, 2003; Yen et al., 2002). In an attempt to develop a more etiologically useful clinical description of these effects, several authors have proposed the existence of a new diagnostic category variously known as complex PTSD or DESNOS – disorders of extreme stress not otherwise specified – characterized by disturbances in affective, self, and interpersonal capacities (Herman, 1992; Zlotnick et al., 1996). Although not formally accepted in DSM as a diagnostic category, emerging evidence supports the proposed inclusion of complex PTSD in ICD-11 as a “sibling” disorder to PTSD (Cloitre et al., 2013; Maercker et al., 2013).
There is somewhat less research to inform our understanding of gender and traumatic stress at the other end of the life span. In a reanalysis of one of the few studies to include individuals over the age of 55, Norris and colleagues (2002) found that age interacted with gender to predict current PTSD. Although higher prevalence rates of PTSD were apparent for women aged 18–55 compared to men in that age range, rates did not differ by gender for those over 55. Interestingly, and perhaps not surprisingly, the higher levels of trauma exposure routinely reported for males only applied to the population under 30 years of age. From approximately 30 onwards, rates of trauma exposure did not differ between women and men. In a comparison of older and younger women, Acierno et al. (2002) found that women over the age of 55 reported fewer physical and sexual assaults, as well as a reduced risk of trauma-related morbidity following interpersonal violence, than women aged 18–34. Finally, Creamer and Parslow (2008) found a clear trend of reduced prevalence of current PTSD over the life span in both women and men, with the highest rates in young adults and negligible rates in those over the age of 65. Indeed, those rates were so low that meaningful gender comparisons were not possible.
In summary, it appears that women are more vulnerable to developing PTSD from a relatively young age, with this gender difference persisting through middle adulthood but being less apparent in the older adulthood period during which there is a reduced rate of PTSD for both genders.
Possible explanations for gender differences in PTSD
A review of epidemiological research thus indicates that women are more vulnerable to the development of PTSD than males. While this might to some extent be influenced by environmental and cultural factors and early childhood experiences, these factors cannot fully account for the differential rates. This section describes a number of other factors that may interact to mediate the relationship between gender, trauma exposure and PTSD vulnerability.
Assessment and phenomenology
It is conceivable that gender differences in the prevalence of PTSD may, in part, be simply an artifact of the diagnostic criteria and assessment procedures. Several studies have reported gender-related differences in patterns of PTSD symptomatology that may increase the likelihood that women will meet criteria for PTSD. More women, for example, have been found to endorse avoidance symptoms in both DSM- (Breslau et al., 1999; Fullerton et al., 2001) and ICD-defined PTSD (Peters et al., 2006). Avoidance and numbing symptoms are relatively infrequently endorsed (e.g., Foa et al., 1995; North et al., 1999); hence, the presence of this symptom criterion substantially increases the likelihood of a PTSD diagnosis. Of note, a latent class analysis conducted on data collected from individuals with PTSD found no evidence of gender-related differential symptom reporting in each of three classes of PTSD-related disturbance: no, intermediate and pervasive disturbance (Chung & Breslau, 2008). The finding that proportionally more women than men experienced pervasive disturbance led the authors to conclude that this is likely to reflect a substantive difference between women and men in their vulnerability to develop PTSD rather than a gender-related reporting bias.
Peritraumatic dissociation, including time distortion, reduced awareness, emotional numbing, amnesia and derealization experienced at the time or soon after the trauma, has been found to be an important risk factor for PTSD (Ozer et al., 2003). There is some evidence that the presence of peritraumatic dissociation predicts PTSD more accurately in women than in men (e.g., Bryant & Harvey, 2003; Fullerton et al., 2001; Irish et al., 2011). For example, Irish and colleagues (2011) found that peritraumatic dissociation contributed to gender differences in PTSD symptoms among MVA victims at 6 months. The mechanisms underlying this relationship require further investigation, although a range of pre- and post-trauma factors are likely to be involved. However, it is difficult to disentangle this finding from the role of prior trauma; adverse early childhood experiences may promote the use of dissociation as a coping strategy in response to stress and trauma, thereby increasing vulnerability to subsequent PTSD.
Importantly, gender differences are not limited to the prevalence of PTSD: women are also more likely than men to be diagnosed with other anxiety and depressive disorders (Kessler et al., 2005; Kessler et al., 1994; Korten & Henderson, 2000; Oakley Browne et al., 2006; Slade et al., 2009). Estimates of PTSD prevalence may be complicated by the substantial overlap of symptoms between PTSD and other anxiety and depressive disorders. Thus, increased rates of PTSD in women may reflect a broader vulnerability to negative affect or at least a willingness to acknowledge and report emotional distress. While elevated rates of PTSD, as well as anxiety and depression in women may reflect a heightened vulnerability to emotional disorders, they may also reflect biases in the diagnostic criteria and assessment processes (see for example Martin et al., 2013 for a discussion of the influence of diagnostic criteria on the prevalence of depression in women and men. Also see Chapters 8, 19, and 20).
Trauma type
A second, and highly plausible, explanation for the higher PTSD prevalence among women is that women and men are prone to experience different types of trauma. Epidemiological studies and systematic reviews have consistently found that girls and women are more likely to report sexual assault, rape and childhood sexual abuse; whereas boys and men are more likely to experience nonsexual physical assault, combat, accidental injury and witnessing someone being badly injured or killed (Amstadter et al., 2013; Breslau et al., 1999; Breslau et al., 1997; Creamer, et al, 2001; Kessler et al., 1995; McLaughlin et al., 2013; Tolin & Foa, 2006). There is a large body of evidence indicating that exposure to traumas involving interpersonal violence carries a high risk of subsequent psychological adjustment problems (e.g., Creamer et al., 2001; Kessler et al., 1995). It is also reasonable to assume that some types of interpersonal violence (and even some types of sexual assault) are especially “psychopathogenic” and more likely to result in poorer psychological adjustment when, for example, the attacker is known to, and previously trusted by, the victim and/or when the level of perceived threat is very high. As a result, it is conceivable that a higher rate of these types of trauma among women might contribute to gender differences in the prevalence of PTSD.
One way to test this hypothesis is to examine whether there are gender differences in the prevalence of PTSD among both women and men who have experienced the same type of event (i.e., control for the type of trauma). If similar rates of PTSD are found for both genders, then this finding would indicate that it is the differences in the types of trauma that men and women report being exposed to that represents the main contributor to PTSD risk. However, if gender differences are evident, then alternative explanations for the higher rates of PTSD in women compared to men are required.
To this end, Tolin and Foa (2006) undertook a meta-analysis of gender differences in trauma and PTSD and found that overall women were more likely to meet criteria for PTSD and reported greater severity of PTSD symptoms compared to men for all types of trauma. Of note, the few available studies that investigated adult sexual assault or child sexual assault did not find gender differences in rates of PTSD, although for child sexual assault significant differences did emerge under certain methodological conditions (e.g., assessment of lifetime versus current PTSD; use of diagnostic interviews versus self-report questionnaires). However, for traumas experienced more frequently by men – such as nonsexual assault, combat, accidental injury and witnessing someone being badly injured or killed – women were more likely to meet criteria for PTSD and reported greater severity of PTSD than men. Taken together, these findings indicate that the higher prevalence of PTSD in women is not simply the result of increased exposure to certain types of trauma. Interestingly, the results of the meta-analysis showed that the greatest gender difference in conditional risk for PTSD was for nonsexual physical assault. Betts and colleagues (2013) also found that women were at a much greater risk of partial and full PTSD after experiencing physical assault, but did not find any gender-related difference in risk of PTSD resulting from other types of traumas. It may be speculated that these findings can at least in part be explained by the type of assaultive violence women experience; that is, women are more likely to be assaulted by someone they know (and, perhaps, trust), while men are more likely to be assaulted by a stranger (for example, in a bar room brawl). Clearly, the former event type is more likely to shatter fundamental assumptions about the self and the world, particularly those relating to trust and safety, creating greater challenges for subsequent adjustment.
Social and material support
It has been suggested that loss of resources in the aftermath of trauma, including both social and material support, may help to explain the development of PTSD and, further, that women are more vulnerable to such resource loss than men (Hobfoll, Johnson, Ennis, & Jackson, 2003). In a sample of 714 inner city women, Hobfoll and colleagues (2003) found that resource loss and worsening economic circumstances had a greater negative impact than resource gain and improving economic circumstances had a positive impact, suggesting the greater saliency of loss than gain. Perhaps the most important “resource” following trauma is that of social support, with lack of social support a powerful predictor of PTSD (Brewin et al., 2000; Ozer et al., 2003). Although measurement of social support is notoriously difficult, it usually encompasses several aspects such as availability, use and perceived benefits of both practical and emotional support. However, an important distinction has been drawn between positive and negative social support. In a sample of crime victims, Andrews and her colleagues (2003) found that perceived positive social support had a protective effect, while perceived negative response from friends and family had a detrimental effect on self-reported PTSD symptoms at 6 months. While women and men reported comparable levels of positive support and support satisfaction, women reported higher levels of negative support (even after controlling for trauma type). Furthermore, the benefits of support satisfaction and the adverse effects of negative support were far more influential on 6-month PTSD symptoms for women than men. This factor contributed substantially to the explanation of gender differences in symptom severity, and is clearly an important direction for future research. Another issue that requires further study is potential gender differences in the source and context of social support that facilitates recovery. For example, research conducted with military personnel found that for men, social support from within the military was associated with lower levels of post-traumatic stress, while support from outside the military (i.e., from family and friends) had no effect. For female personnel, the reverse was true (Smith et al., 2013). In summary, the available evidence suggests that social support, and particularly negative social support, is likely to interact with acute symptom severity to influence the course of recovery following trauma.
Cognitive factors
Epidemiological studies, such as those described earlier, often focus on objective trauma type and severity. It is widely recognized, however, that the individual’s perception or appraisal of threat level is a powerful predictor of subsequent adjustment (Ehlers & Clark, 2000). There is some evidence to suggest that women may perceive traumatic events as more aversive than men who experience the same event. Norris and colleagues (2002) noted that comparable proportions of women and men meet the DSM-IV Criterion A2 (powerful emotional reactions to trauma), despite the fact that men report a higher prevalence of objective trauma exposure. Goenjian and colleagues (2001) found that Nicaraguan adolescent girls reported significantly higher subjective levels of exposure than adolescent boys, despite no difference in their objective experience of Hurricane Mitch. Thus, girls and women may tend subjectively to experience traumatic events as more aversive, with these negative appraisals increasing vulnerability to PTSD. In some circumstances, it is understandable that women may feel more threatened by a traumatic event, particularly if the experience involves intentional harm. For example, it is plausible that a woman who is a victim of nonsexual assault by a male perpetrator may also fear that the perpetrator will rape her. Thus, an assault of the same objective severity may at times be considerably more frightening for a woman than for a man. Another cognitive factor that may contribute to the development of PTSD is negative appraisal of acute symptoms following trauma, including beliefs that the symptoms signify personal weakness or impending madness (McNally, 2003). At present, however, there is a lack of empirical data on gender differences in how women and men interpret acute trauma symptoms.
The important role of cognitive factors in the development of PTSD has strong theoretical support, as discussed by Tolin and Foa (2002). These authors build on the emotional processing theory described by Foa and her colleagues (e.g., Foa & Rothbaum, 1998) to explore differential patterns of cognitive processing between women and men that may serve to increase PTSD vulnerability. Emotional processing theory proposes that the development of traumatic stress symptoms is dependent upon an individual’s prior perception of the self and the world, as well as the degree to which these views change as a consequence of trauma. Tolin and Foa (2002) reviewed the literature and found preliminary evidence to support the proposition of gender differences in patterns of cognitive processing, memory of the event, and the effect of trauma on cognitive schemas. Self-blame was more prevalent in women than men following trauma, as were negative self-beliefs and perceptions of the world as a dangerous place. It is, of course, difficult to separate the influence of trauma type from cognitive appraisals; traumas that are objectively more severe are also likely to be appraised more negatively. It was noted earlier, however, that trauma type accounted for only a limited amount of the variance in post-traumatic stress levels, suggesting that cognitive processing patterns may mediate vulnerability to PTSD. Again, the underlying mechanisms that explain these gender differences in processing of information associated with the trauma remain a matter for speculation (Olff et al., 2007). Presumably, the difference is accounted for by a complex interaction between a range of influences.
Biological factors
Few studies have investigated psychophysiological differences between men and women in acute reactions to threat that may serve as potential mediators for PTSD vulnerability. A review of the empirical data by Pierce and colleagues (2002) suggested that there was little evidence for gender-specific differences in physiological responses (such as cardiovascular and skin conductance reactivity) to threat-related stimuli. They acknowledged, however, that studies are lacking and that those that exist have methodological limitations. A more recent review reported that any evidence for gender differences in physiological reactivity seemed to depend on how it was operationalized in particular studies (McLean & Anderson, 2009).
Greater support has been found for the impact of hormone fluctuations across the life span in mediating response to stress cues and vulnerability to anxiety disorders. Piggott (1999) reported that estrogen and progesterone have been associated with the regulation of neurotransmitters that mediate the anxiety response. These include the locus coeruleus-noradrenaline and serotonergic systems, as well as the y-aminobutyric acid (GABA) benzodiazepine receptor complex. Higher levels of estrogen are proposed to be stress-protective while progesterone may have the reverse effect. Fluctuations in these hormones during a woman’s menstrual and reproductive cycle may influence the degree of reactivity to stress cues and the course of symptomatology. A review by Kajantie and Phillips (2006) concluded that adult women between puberty and menopause tend to be less physiologically reactive to stress than men, are more reactive during the luteal phase of the menstrual cycle, and less reactive during pregnancy and after menopause. Consistent with this summary, more recent research suggests that the luteal phase and the associated increase in progesterone is predictive of enhanced recall of negative events (Felmingham et al., 2012), and increased risk of flashbacks (Bryant et al., 2011). Thus, it would seem that gender differences in physiological reactivity are influenced by women’s hormonal status (see Chapter 8).
In summary, it is likely that several factors interact to explain the higher rates of PTSD among women. These include cultural and societal pressures and expectations (see Chapter 1), the types of trauma to which women are more likely to be exposed, the reaction of loved ones and associates to their experience, and hormonal levels. It is likely that these factors combine to influence cognitive processing and appraisals of the trauma, which, in turn, affect the course of recovery. While it is possible that the diagnostic criteria and common assessment strategies serve to inflate artificially the reported prevalence of PTSD, this seems an unlikely and unhelpful explanation. Rather than denying the existence of these elevated rates, a more productive approach is to focus upon what can be done to address the causes of this differential vulnerability and how best to treat those affected.
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