**3.2.3 Post-traumatic risk factors**

When it comes to post-traumatic risk factors associated with PTSD, sex differences in the use of coping strategies have been repeatedly reported. Females tend to use more emotionfocused coping strategies, such as support seeking, than males (e.g. Tamres et al., 2002). Furthermore, although males do not use any coping style more often than do females, overall, they do appear to use relatively more problem-focused and avoidance coping than females (Tamres et al., 2002), and they are more likely than females to choose problemfocused coping as their initial coping strategy (Ptacek et al., 1992). Whereas a problemfocused coping style has shown to serve as a protective factor against PTSD, both avoidant and emotion-focused coping have been reported to be related to increased PTSD severity (Bödvarsdóttir & Elklit, 2004; Gil, 2005). It is thus possible that the use of emotion-focused coping may to some degree account for the increased prevalence of PTSD in females (Peirce et al., 2002). However, O'Connor & Elklit (2008) found that neither problem-focused nor avoidant coping was significantly associated with lifetime PTSD severity, and that sex remained a significant predictor of PTSD severity after emotion-focused coping was controlled for.

In addition to differences in coping strategies, females are more likely to blame themselves for the trauma and to see themselves and the world in a negative light following a PTE, and such post-traumatic cognitions have been found to predict PTSD (Cromer & Smyth, 2010). Thus, it could be expected that sex differences in post-traumatic cognitions may help account for the increased rate and severity of PTSD in females compared to males. However, one study found that self-blame and negative cognitions about the world and oneself failed to account for sex differences in students' PTSD symptoms (Cromer & Smyth, 2010). And another study reported that although sex was no longer significantly associated with PTSD symptoms after the same three post-traumatic cognitions and interactions with sex had been controlled for, negative cognitions about oneself was actually more strongly associated with PTSD symptoms in males than in females, suggesting that such post-traumatic cognitions in females are unlikely to account for sex differences in PTSD severity.

#### **3.3 Evaluation of the mediation hypothesis**

Together, the structural and socialisation theories offer a valid gender-based approach to sex differences in PTSD. However, gender influences are generally very difficult to discern from sex differences and can often be equally well explained by biologically based theories. For example, it was reported that a traditionally masculine response style could at least partly explain why female police officers reported lower levels of PTSD than female civilians, and

account for any additional difference in PTSD levels. In contrast, Irish et al. (2011) found that perceived life threat could not account for sex differences in PTSD severity after an MVA, but that peritraumatic dissociation served as a partial mediator of 6 week and 6 month PTSD severity. Finally, Spindler et al. (2010) found that sex was no longer significantly associated with PTSD status in a logistic regression analysis after perceived life threat was controlled for, whereas two other studies have found that neither peritraumatic dissociation or perceived threat (Ehlers et al., 1998) nor peritraumatic helplessness or horror (O'Connor & Elklit, 2008) could eliminate sex as a risk factor for PTSD. Thus, contradictory findings have been reported on whether sex differences in peritraumatic reactions can account for sex

When it comes to post-traumatic risk factors associated with PTSD, sex differences in the use of coping strategies have been repeatedly reported. Females tend to use more emotionfocused coping strategies, such as support seeking, than males (e.g. Tamres et al., 2002). Furthermore, although males do not use any coping style more often than do females, overall, they do appear to use relatively more problem-focused and avoidance coping than females (Tamres et al., 2002), and they are more likely than females to choose problemfocused coping as their initial coping strategy (Ptacek et al., 1992). Whereas a problemfocused coping style has shown to serve as a protective factor against PTSD, both avoidant and emotion-focused coping have been reported to be related to increased PTSD severity (Bödvarsdóttir & Elklit, 2004; Gil, 2005). It is thus possible that the use of emotion-focused coping may to some degree account for the increased prevalence of PTSD in females (Peirce et al., 2002). However, O'Connor & Elklit (2008) found that neither problem-focused nor avoidant coping was significantly associated with lifetime PTSD severity, and that sex remained a significant predictor of PTSD severity after emotion-focused coping was

In addition to differences in coping strategies, females are more likely to blame themselves for the trauma and to see themselves and the world in a negative light following a PTE, and such post-traumatic cognitions have been found to predict PTSD (Cromer & Smyth, 2010). Thus, it could be expected that sex differences in post-traumatic cognitions may help account for the increased rate and severity of PTSD in females compared to males. However, one study found that self-blame and negative cognitions about the world and oneself failed to account for sex differences in students' PTSD symptoms (Cromer & Smyth, 2010). And another study reported that although sex was no longer significantly associated with PTSD symptoms after the same three post-traumatic cognitions and interactions with sex had been controlled for, negative cognitions about oneself was actually more strongly associated with PTSD symptoms in males than in females, suggesting that such post-traumatic cognitions in

Together, the structural and socialisation theories offer a valid gender-based approach to sex differences in PTSD. However, gender influences are generally very difficult to discern from sex differences and can often be equally well explained by biologically based theories. For example, it was reported that a traditionally masculine response style could at least partly explain why female police officers reported lower levels of PTSD than female civilians, and

females are unlikely to account for sex differences in PTSD severity.

**3.3 Evaluation of the mediation hypothesis** 

differences in PTSD.

controlled for.

**3.2.3 Post-traumatic risk factors** 

it was suggested that such differences were due to the masculine socialisation of police officers (Lilly et al., 2009). However, it could be argued that the women who choose to become police officers already differ from women who do not on a number of variables relevant to the development of PTSD. Such differences (which may be accounted for either by prior socialisation processes or differences in hormone levels and other physiological factors) may account for the similar PTSD prevalence found in male and female police officers better than any police-specific socialisation processes.

In sum, sex differences in the risk factors associated with PTSD may account for at least part of the increased prevalence of PTSD in females, and several studies have shown that when included in hierarchical regression models, sex often becomes non-significant after other variables are controlled for. This has led many researchers to conclude that the role of sex in PTSD research is not as important as has previously been assumed (e.g. Ozer et al., 2003). However, other studies have found that sex remains a significant predictor of PTSD severity even after risk factors, which are more prevalent in females have been controlled for (e.g. Ehlers et al., 1998, O'Conner & Elklit, 2008). In order to fully test the mediation hypothesis, specific mediation studies need to be conducted, which make an effort to include all risk factors known to be more prevalent in females. However, research on sex differences in PTSD is still in its childhood, and viewing sex simply as a risk factor or as a control variable may be too simplistic. We believe that sex differences in PTSD go much deeper than simple mediation effects. In addition to sex differences in the prevalence of PTSD, sex differences may also exist in the physiological response to trauma and in how such reactions may shape symptom development. The latter part of this chapter will focus on these less studied sex differences in PTSD.

#### **4. Sex differences in initial trauma response**

It is generally accepted, that confrontation with a stressor results in immediate activation of the sympathetic nervous system (SNS) and release of the catecholamines epinephrine and norepinephrine, which encourage either fighting or fleeing behaviour. The activation of the SNS further stimulates the slower stress response of the hypothalamic-pituitary-adrenal (HPA) axis. This triggers the release of corticotropin releasing hormone (CRH), adrenocorticotropin hormone (ACTH), and glucocorticoids, particularly cortisol. However, the physiological stress response in males has been much more extensively studied than is the case for females (Peirce et al., 2002). Furthermore, both-sex studies are often based on small samples without sufficient power to detect sex differences. This is highly problematic because important sex differences have been reported in the HPA response to stress (Kirschbaum et al., 1999).

Arginine vasopressin (AVP) and oxytocin are two peptide hormones induced by the HPA axis. Even though AVP and oxytocin are structurally similar and differ from each other by only two amino acids (Klein & Corwin, 2002), the two hormones differ widely in the roles they play in response to stress. Whereas AVP stimulates the fight-or-flight response and HPA axis activation (Klein & Corwin, 2002), oxytocin appears to suppress the HPA response to stress and be regulated by the parasympathetic nervous system (PNS; Klein & Corwin, 2002; Neumann, 2008; Neumann et al., 2000). AVP levels are higher in males than in females and may be regulated by testosterone (Rasmusson et al., 2002). In contrast, oxytocin levels are higher in females, and the bio-behavioural effects of oxytocin are enhanced by oestrogen (Klein & Corwin, 2002). Furthermore, there is preliminary evidence that the two female sex

suggests that gender roles may affect, which characteristics of an event are considered stressful by males and females and such differences affect the psychobiological stress response and may further affect the risk of developing PTSD. Thus, even though the fightor-flight system exists in females, the tend-and-befriend system is assumed to dominate in times of danger. However, despite sex differences in the normal response to trauma, it is important to note that there are intra-sex differences. Geary and Flynn (2002) have pointed out that males do not always react to stress with fight-or-flight behaviour and that in some situations males respond to stress in ways similar to the tend-and-befriend response in females. With the tend-and-befriend and the fight-or-flight system operating in both sexes, intra-sex differences in the initial trauma response are likely to depend upon intra-sex

variations in hormone levels as well as socialisation and gender role expectations.

previously been suggested (Christiansen & Elklit, 2008).

pronounced in boys than in girls (Kaplow et al., 2005).

**5. Sex-specific pathways to PTSD** 

Little is known about which factors contribute to the shift from adaptive responses during and immediately following the traumatic event to maladaptive responses, which may be related to PTSD in the long run (Paris et al., 2010). However, it is likely that sex differences in the initial stress response may persist beyond the traumatic event and affect the development and maintenance of PTSD. Perry and colleagues (1995) have suggested that neural responses to stress may become sensitised, resulting in the same neural responses being elicited by decreasingly intense stimuli. The tend-and-befriend versus fight-or-flight theory proposed by Taylor and colleagues may thus be highly relevant to include in a theory of sex differences in PTSD, as it is possible that sex differences in the initial response to trauma may lead males and females to follow different pathways to PTSD, as has

Perry and colleagues (1995) suggested that two neuronal response patterns could be identified in traumatised children. The first behaviour pattern was assumed to be associated with a sensitisation of the catecholamine system (in accordance with increased activation of the SNS) resulting in hyperarousal in response to traumatic reminders. The other behaviour pattern was assumed to be associated with a decrease in blood pressure and heart rate (consistent with a down-regulation of the SNS). This latter behaviour pattern was initiated by an attempt to seek protection from the caretaker, which in the case of persistent threat was followed by a range of more and more dissociative symptoms, including compliance, freezing, and complete dissociation (Perry et al., 1995). In accordance with this theory, two separate pathways to PTSD have been identified in a study of child burn victims (Saxe et al., 2005). One pathway was mediated by dissociation, the other by anxiety/arousal. The two pathways were separated by different risk factors, suggesting that different bio-behavioural systems may be involved in the development and maintenance of PTSD. More specifically, the anxiety/arousal pathway is likely to be related to the fight-or-flight system controlled by the SNS and the HPA axis, whereas the dissociation pathway may be connected to the animal "freeze" response, which appears to be controlled by the PNS (Saxe et al., 2005). This study did not report any sex differences in the two pathways, but another study focusing on sexually abused children found support for the existence of an anxiety/arousal pathway and a dissociation pathway as well as a third avoidance pathway, which was more

We do not know of any studies examining the existence of different pathways to PTSD in adults. However, the argument that the anxiety/arousal pathway should be linked to an

hormones oestrogen and progesterone are associated with blunted vascular reactivity to acute stressors (Peirce et al., 2002). Thus, oxytocin appears to play a greater role in females compared to males, and as a result females may be more prone to react to acute stress with a suppression of the HPA axis and the SNS in response to stress. In contrast, higher levels of AVP in males are associated with increases in HPA and SNS activity in the face of threat, consistent with a fight-or-flight response. This apparent sex difference is supported by the finding that males appear to respond to stressful events with greater increases in cortisol than do females, which may reflect a tendency to HPA hyper-reactivity in males and hyporeactivity in females (Kudielka & Kirschbaum, 2005).

Taylor et al. (2000) have suggested that whereas males respond to stress with the wellknown fight-or-flight system regulated by the SNS, evolutionary demands have favoured an alternative tend-and-befriend system in females regulated by the PNS. This alternative response to stress is hypothesised to have developed because it has been more adaptive for females in times of threat to tend to offspring and seek protection among other members of the group. The tend-and-befriend system is hypothesised to be linked to oxytocin, which is implicated in a variety of social behaviours relevant to how females respond in the aftermath of trauma, including social support and coping (Taylor, 2006; Taylor et al., 2002). In support of the tend-and-befriend theory, it has been documented that males generally respond to stressful events with physiological hyperarousal and an increase in aggressive behaviours, whereas females are more likely to group together and seek social support – especially from other females (Taylor et al., 2000). Kivlighan and colleagues (2005) found that activation of the HPA axis evidenced by increases in cortisol levels in preparation for a rowing competition was associated with increased competitiveness and more pre-race mental preparation in males but with bonding and social affiliation with teammates in females. Furthermore, a study of 18-month-old children has reported sex differences in the response to frightening maternal behaviour (David & Lyons-Ruth, 2005). Whereas males responded by displaying pronounced avoidance, resistance, and conflict behaviour, females responded by approaching their mothers while simultaneously displaying behaviours such as hesitation, fearfulness, and freezing. In accordance with this dissociation-like behaviour in female toddlers, adult females use more dissociative mechanisms in the face of trauma compared to males (Bryant & Harvey, 2003; Irish et al., 2011). Dissociation appears to be linked to a suppression of activity in the sympathetic nervous system and the HPA axis (Olff et al., 2007).

Some of the differences in the male and female response to stress, which have been discussed here, appear to be best explained by biological sex differences. For instance, several of the hormones involved in HPA activation appear to be affected by the female menstrual cycle (Kudielka & Kirschbaum, 2005), and sex differences in the physiological response to stress appear to be present very early in life (David & Lyons-Ruth, 2005; Kudielka & Kirschbaum, 2005). However, depression research has indicated ways in which both environmental and genetic factors can lead to changes in HPA reactivity (Swaab et al., 2000), and studies indicate that sex differences in the epinephrine response to cognitive challenge is mediated by gender role (Davis & Emory, 1995). Further support for the influence of gender roles can be found in one study, which reported that confrontation with achievement challenges involving performance failures resulted in increased free cortisol levels in males but not in females (Kudielka & Kirschbaum, 2005). In contrast, social rejection challenges resulted in significant increases in females, but not in males, indicating that different stressors may lead to activation of the HPA axis in males and females. This

hormones oestrogen and progesterone are associated with blunted vascular reactivity to acute stressors (Peirce et al., 2002). Thus, oxytocin appears to play a greater role in females compared to males, and as a result females may be more prone to react to acute stress with a suppression of the HPA axis and the SNS in response to stress. In contrast, higher levels of AVP in males are associated with increases in HPA and SNS activity in the face of threat, consistent with a fight-or-flight response. This apparent sex difference is supported by the finding that males appear to respond to stressful events with greater increases in cortisol than do females, which may reflect a tendency to HPA hyper-reactivity in males and hypo-

Taylor et al. (2000) have suggested that whereas males respond to stress with the wellknown fight-or-flight system regulated by the SNS, evolutionary demands have favoured an alternative tend-and-befriend system in females regulated by the PNS. This alternative response to stress is hypothesised to have developed because it has been more adaptive for females in times of threat to tend to offspring and seek protection among other members of the group. The tend-and-befriend system is hypothesised to be linked to oxytocin, which is implicated in a variety of social behaviours relevant to how females respond in the aftermath of trauma, including social support and coping (Taylor, 2006; Taylor et al., 2002). In support of the tend-and-befriend theory, it has been documented that males generally respond to stressful events with physiological hyperarousal and an increase in aggressive behaviours, whereas females are more likely to group together and seek social support – especially from other females (Taylor et al., 2000). Kivlighan and colleagues (2005) found that activation of the HPA axis evidenced by increases in cortisol levels in preparation for a rowing competition was associated with increased competitiveness and more pre-race mental preparation in males but with bonding and social affiliation with teammates in females. Furthermore, a study of 18-month-old children has reported sex differences in the response to frightening maternal behaviour (David & Lyons-Ruth, 2005). Whereas males responded by displaying pronounced avoidance, resistance, and conflict behaviour, females responded by approaching their mothers while simultaneously displaying behaviours such as hesitation, fearfulness, and freezing. In accordance with this dissociation-like behaviour in female toddlers, adult females use more dissociative mechanisms in the face of trauma compared to males (Bryant & Harvey, 2003; Irish et al., 2011). Dissociation appears to be linked to a suppression of activity in the sympathetic nervous system and the HPA axis (Olff

Some of the differences in the male and female response to stress, which have been discussed here, appear to be best explained by biological sex differences. For instance, several of the hormones involved in HPA activation appear to be affected by the female menstrual cycle (Kudielka & Kirschbaum, 2005), and sex differences in the physiological response to stress appear to be present very early in life (David & Lyons-Ruth, 2005; Kudielka & Kirschbaum, 2005). However, depression research has indicated ways in which both environmental and genetic factors can lead to changes in HPA reactivity (Swaab et al., 2000), and studies indicate that sex differences in the epinephrine response to cognitive challenge is mediated by gender role (Davis & Emory, 1995). Further support for the influence of gender roles can be found in one study, which reported that confrontation with achievement challenges involving performance failures resulted in increased free cortisol levels in males but not in females (Kudielka & Kirschbaum, 2005). In contrast, social rejection challenges resulted in significant increases in females, but not in males, indicating that different stressors may lead to activation of the HPA axis in males and females. This

reactivity in females (Kudielka & Kirschbaum, 2005).

et al., 2007).

suggests that gender roles may affect, which characteristics of an event are considered stressful by males and females and such differences affect the psychobiological stress response and may further affect the risk of developing PTSD. Thus, even though the fightor-flight system exists in females, the tend-and-befriend system is assumed to dominate in times of danger. However, despite sex differences in the normal response to trauma, it is important to note that there are intra-sex differences. Geary and Flynn (2002) have pointed out that males do not always react to stress with fight-or-flight behaviour and that in some situations males respond to stress in ways similar to the tend-and-befriend response in females. With the tend-and-befriend and the fight-or-flight system operating in both sexes, intra-sex differences in the initial trauma response are likely to depend upon intra-sex variations in hormone levels as well as socialisation and gender role expectations.

Little is known about which factors contribute to the shift from adaptive responses during and immediately following the traumatic event to maladaptive responses, which may be related to PTSD in the long run (Paris et al., 2010). However, it is likely that sex differences in the initial stress response may persist beyond the traumatic event and affect the development and maintenance of PTSD. Perry and colleagues (1995) have suggested that neural responses to stress may become sensitised, resulting in the same neural responses being elicited by decreasingly intense stimuli. The tend-and-befriend versus fight-or-flight theory proposed by Taylor and colleagues may thus be highly relevant to include in a theory of sex differences in PTSD, as it is possible that sex differences in the initial response to trauma may lead males and females to follow different pathways to PTSD, as has previously been suggested (Christiansen & Elklit, 2008).

### **5. Sex-specific pathways to PTSD**

Perry and colleagues (1995) suggested that two neuronal response patterns could be identified in traumatised children. The first behaviour pattern was assumed to be associated with a sensitisation of the catecholamine system (in accordance with increased activation of the SNS) resulting in hyperarousal in response to traumatic reminders. The other behaviour pattern was assumed to be associated with a decrease in blood pressure and heart rate (consistent with a down-regulation of the SNS). This latter behaviour pattern was initiated by an attempt to seek protection from the caretaker, which in the case of persistent threat was followed by a range of more and more dissociative symptoms, including compliance, freezing, and complete dissociation (Perry et al., 1995). In accordance with this theory, two separate pathways to PTSD have been identified in a study of child burn victims (Saxe et al., 2005). One pathway was mediated by dissociation, the other by anxiety/arousal. The two pathways were separated by different risk factors, suggesting that different bio-behavioural systems may be involved in the development and maintenance of PTSD. More specifically, the anxiety/arousal pathway is likely to be related to the fight-or-flight system controlled by the SNS and the HPA axis, whereas the dissociation pathway may be connected to the animal "freeze" response, which appears to be controlled by the PNS (Saxe et al., 2005). This study did not report any sex differences in the two pathways, but another study focusing on sexually abused children found support for the existence of an anxiety/arousal pathway and a dissociation pathway as well as a third avoidance pathway, which was more pronounced in boys than in girls (Kaplow et al., 2005).

We do not know of any studies examining the existence of different pathways to PTSD in adults. However, the argument that the anxiety/arousal pathway should be linked to an

a number of new analyses on previously published data based on two separate samples (see Christiansen & Elklit, 2008). One sample consisted of residents in an area, which had been almost completely destroyed by an industrial disaster (the explosion sample), the other consisted of high school students who had witnessed a stabbing incident, were a young girl was killed (the high school sample). In contrast to the original analysis, this time we used only the symptoms included in the DSM-IV to measure PTSD severity (i.e. the first 17 items of the Harvard Trauma Questionnaire; Mollica et al., 1992). As can be seen in Table 1, we found no significant sex differences in correlations between feeling let down by others and PTSD severity, and positive social support was unrelated to PTSD severity in both males and females in the explosion sample. However, we did find that positive social support was significantly more strongly correlated with PTSD severity in females compared to males in the high school sample. There thus appears to be some support for the hypothesis that sex

let down a Dissociation a Anxiety Em.

Males -.18 / -.05 .50\*\*/ .33\*\* .56\*\* / .44\*\* .73\*\* .66\*\* -.02 .32\*\* Females -.14 / -.35\*\* .36\*\* / .45\*\* .62\*\* / .68\*\* .57\*\* .75\*\* -.16 .27\* *z* n.s. / 2.51\* n.s. / n.s. n.s. / -2.96\*\* 1.73 b n.s. n.s. n.s. Pearson coefficients between risk factors and PTSD severity (combined score on the 17 first HTQ items) are shown separately for males and females from the explosion study and the high school stabbing

a r values from the explosion study / r values from the stabbing incident study \* *<sup>p</sup>* < .05; \*\* p < .01; b *<sup>p</sup>* = .08; n.s.: not significant

The impact of sex on the relationship between social support and PTSD is further complicated by the possibility that different types of support may have differential impact on PTSD symptomatology in males and females. For example, it is possible that talking about the traumatic event may be preferable for females, whereas males may appreciate practical assistance more, because such types of support are most compatible with the preferred coping strategies used by each sex. Furthermore, males as well as females depend mostly on female providers of support, and whereas females often have multiple support sources, adult males often cite their spouses as their only confidantes (Shumaker & Hill, 1991). This may be the reason why being unmarried serves as a risk factor for mortality in males to a greater extent than is the case for females (Shumaker & Hill, 1991). Thus, whereas females may be more vulnerable to lack of support and negative reactions from others more generally, males may be more dependent on the support of their spouse and thus be relatively more vulnerable to PTSD in case of separation or spousal bereavement. In accordance with this idea, a study on elderly bereaved has reported a lack of sex differences in PTSD severity (Elklit & O'Connor, 2005), which is in contrast to the otherwise well-

The apparent role of AVP in the acute male stress response points to the possibility that arousal may predict PTSD in males more strongly than in females, and that males may be

Em. cop.: emotion-focused coping; rat. cop.: rational coping; Avoi. cop.: avoidance coping. Table 1. Correlations between risk factors and PTSD severity for males and females

cop.

Probl. cop.

Avoi. cop.

moderates the relationship between social support and PTSD.

Feeling

established increased prevalence of PTSD among females.

Positive support a

incident.

**6.2 Anxiety/arousal** 

activation of the HPA axis and the SNS corresponds to the male stress response proposed above. Similarly, the idea that the dissociation pathway should be linked to the PNS is in accordance with the female stress response. There thus appears to be some overlap between the findings concerning different pathways to PTSD in children and sex differences in the initial stress response in adults. This suggests, that even though the two studies on pathways in children did not report any sex differences in the anxiety/arousal and dissociation pathways, males may be more likely to follow an anxiety/arousal pathway and females a dissociation pathway to PTSD. This is in accordance with the ideas proposed by Perry et al. (1995), who argued that activation and sensitisation of the dissociative response pattern was more common in females than in males, whereas the opposite appeared to be the case for the hyperarousal pattern. Furthermore, although the avoidance pathway identified in the study by Kaplow et al. (2005) was not associated with a specific physiological system, it could be argued that avoidance is a form of fleeing behaviour associated with the fight-or-flight system (Taylor, 2006), and as this pathway was more pronounced in boys than in girls, males may also be more likely to follow an avoidance pathway than females.

If males and females follow different pathways to PTSD, we would expect to find sex differences in the relationship between certain risk factors and PTSD. Whereas research has mainly focused on mediation effects between sex and PTSD, the moderation hypothesis states that there may be sex differences in the relationship between different risk factors and symptomatology (Stone et al., 2010), suggesting that some risk factors may predict PTSD in females but not in males, whereas others may better predict PTSD in males. Furthermore, if such sex-specific pathways are related to the fight-or-flight versus tend-and-befriend response to stress, we would hypothesise that particularly behaviours related to either the tend-and-befriend or the fight-or-flight response to stress would show sex differences in their ability to predict PTSD. For example, physiological processes involved in the tend-andbefriend response, such as activation of the PNS and the role of oxytocin, could make emotion-focused coping, particularly support seeking, social support, and possibly dissociation more closely related to PTSD in females than in males. In contrast, arousal, anxiety, and possibly problem-focused and avoidant coping strategies could be hypothesised to be more important in the development or prevention of PTSD in males compared to females.
