Interpersonal Trauma and PTSD:The Roles of Gender and a Lifespan Perspective in Predicting Risk

Michelle M. Lilly and Christine E. ValdezNorthern Illinois University

Research has shown that women’s increased risk for interpersonal trauma (IPT) may place them atheightened risk for Posttraumatic Stress Disorder (PTSD). However, research has not shown whether thetiming of IPT exposure and revictimization impact PTSD development, and whether this may alsoaccount for observed gender disparities in PTSD. Consensus coding was used to group 180 undergraduateparticipants into one of four IPT exposure groups: no exposure, childhood only, adolescent/adulthoodonly, life span. Women were significantly overrepresented in the life span-exposure group that experi-enced IPT in both childhood and adolescence/adulthood. IPT-group membership significantly predictedPTSD symptoms, with post hoc analyses revealing that the life span-exposure group reported signifi-cantly more PTSD symptoms than the no-exposure and adolescent/adulthood-only groups, but did notdiffer from the childhood-only group. A generalized linear model revealed that when both gender and IPTgroup were considered in relationship to PTSD symptoms, only IPT-group membership significantlypredicted PTSD symptoms.

Keywords: PTSD, interpersonal trauma, gender disparity

Exposure to a potentially traumatic event is not uncommon inthe United States, with community surveys revealing a lifetimeexposure rate of 69% (Norris, 1992; Resnick, Kilpatrick, Dansky,Saunders & Best, 1993). The mental health consequences oftrauma exposure are myriad with a notable percentage of traumaexposed individuals reporting Posttraumatic Stress Disorder(PTSD) or PTSD symptoms. In the National Comorbidity Study,for instance, Kessler et al. (1995) reported a 7.8% lifetime prev-alence rate of PTSD. However, rates of PTSD are marked byconsistent gender disparities. Norris, Foster and Weisshaar (2002)reported an 11.3% lifetime prevalence rate of PTSD in women andonly a 6% lifetime prevalence rate in men. Women are alsooverrepresented in cases of chronic PTSD with 22% of women andonly 6% of men categorized as reporting chronic PTSD (Breslau &Davis, 1992). This raises the question of why women may be atheightened risk for PTSD and overrepresent chronic cases ofPTSD.

Among the more compelling explanations for gender asymme-try in PTSD is that men and women systematically differ in thetypes of traumatic events experienced. Generally, women are morelikely to be exposed to interpersonal forms of trauma such assexual assault, molestation, and partner violence in adulthood, aswell as child abuse (physical or sexual); while men are more likelyto be exposed to fires, disasters, combat, accidents, and physicalassaults at the hands of strangers (Breslau, 2001; Flett, Kazantis,

Long, MacDonald & Millar, 2004; Kessler et al., 1995; McGruderet al., 2000). Interpersonal trauma (IPT) is defined here as trau-matic events in which an individual is personally assaulted orviolated by another human being that is either known or unknownto the trauma survivor. Research has found that IPT typicallyincreases risk for PTSD in comparison to traumatic events that arenoninterpersonal in nature (or criminal vs. noncriminal; Breslau,2001; Luthra, 2009; Resnick et al., 1993), which may partiallyaccount for greater reports of PTSD among women. Further, thetypes of IPT frequently reported by women also tend to occurearlier in life and increase risk for revictimization.

Extensive research has shown that individuals who experiencetrauma early in life, especially childhood sexual abuse prior to theage of 13 or 14, are at greater risk for subsequent revictimizationlater in life, particularly in the form of sexual assault or intimatepartner violence (Arata, 1999a; Cloitre, Tardiff, Marzuk, Leon &Portera, 1996). Additionally, early victimization has been shown toenhance risk for PTSD. Masho and Ahmed (2007) discovered adose-response relationship between time of sexual assault andPTSD diagnosis, with the highest percentage of PTSD diagnosesbeing reported by women who experienced sexual assault for thefirst time at an age younger than 12. Women with repeated IPTvictimization (i.e., women with child sexual abuse histories and aseparate incident of adolescent/adulthood sexual victimization)have also been found to report higher levels of PTSD symptoms(Arata, 2000), and PTSD diagnosis has been found to differentiatebetween women with repeated victimization versus child or adult-only sexual assault (Arata, 1999a).

The present study used consensus coding to create four groupsof undergraduate students: no-IPT exposure, childhood-only IPTexposure, adolescent/adulthood-only IPT exposure, and life-spanIPT exposure. The life-span group consisted of participants thatexperienced IPT in both childhood and adolescence/adulthood. In

This article was published Online First March 28, 2011.Michelle M. Lilly and Christine E. Valdez, Department of Psychology,

Northern Illinois University.Correspondence concerning this article should be addressed to Michelle

M. Lilly, Department of Psychology, Northern Illinois University,Psychology-Computer Science Building, DeKalb, IL 60115. E-mail:[email protected]

Psychological Trauma: Theory, Research, Practice, and Policy © 2011 American Psychological Association2012, Vol. 4, No. 1, 140 –144 1942-9681/11/$12.00 DOI: 10.1037/a0022947

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the coding process, a separate adolescent group was created.However, upon completion of coding the adolescence-only IPTexposure group, only two participants were represented. As such,these participants were grouped with the adulthood IPT exposuregroup. This was decided based on previous research indicating thatchildhood victimization is qualitatively different in outcome thantrauma that occurs after childhood, with cut-off ages for childhoodtypically around 13 to 14 years of age (Arata, 1999b).

The following hypotheses were proposed: (1) Women in thisstudy will be overrepresented in the childhood-only and life-spanIPT groups, while men will be overrepresented in the adolescent/adulthood-only group; (2) There will be significant differencesacross the IPT groups in PTSD symptoms, with the life-span IPTgroup reporting the greatest PTSD symptoms, followed by thechildhood-only group, then the adolescent/adulthood-only group,and then the no-IPT group; (3) The life-span IPT group will reporta greater percentage of PTSD diagnosis cut-off scores than thechildhood-only IPT group; (4) IPT-group membership will be abetter predictor of PTSD symptoms than gender.

Method

Participants and Procedures

Participants consisted of a subsample of undergraduate studentsat a Midwestern university, drawn from a larger survey of 416participants. Students included in this study (n � 180) wereselected based on their ability to identify a traumatic event that“was particularly upsetting” and “has stuck with them for a longtime” (hereafter referenced as an “index worst traumatic event”).This was done in an effort to accurately assess PTSD symptoms asspecified by the Posttraumatic Stress Diagnostic Scale (PDS; Foa,1995). The subsample was 64% female (n � 116) with an averageage of 19.56 (SD � 2.97). Of the subsample, 82% identified asfreshman/sophomore (n � 146) and the majority identified asEuropean American (69%, n � 124).

Participants were recruited through an introductory psychologycourse and elected to participate in an online survey “about ad-verse life events, how they relate to other people and mentalhealth.” Participants indicated a desire to complete the survey bysigning up via an online system that manages available studies. Aninformed consent was presented to the participants online, as wellas a debriefing form upon completion.

At the conclusion of the study, consensus coding was conductedthat assigned participants into one of four categories based onresponses from the Traumatic Life Experiences Questionnaire(TLEQ; Kubany, 2004) by a team of seven undergraduate andgraduate students, under the direction of the first author. Decisionson categorization were made based on endorsement of particularitems and whether the participant reported experiencing “intensefear, helplessness or horror” or injury in reaction to the traumaticevent. If an individual reported that they did not experience intensefear, helplessness or horror, the traumatic event was not consideredin the grouping. Participants were not categorized until a unani-mous decision was made. Four final groups were created: no IPT(n � 70), childhood-only IPT (n � 18; i.e., all IPT occurred priorto 13 years of age), adolescent/adulthood-only IPV (n � 73) andlife-span IPT (n � 19). This suggests that of the subsample ofindividuals that identified a worst index traumatic event, a portion

identified a noninterpersonal traumatic event as an event that wasupsetting and completed the PDS in relationship to that event.Information on the items used to categorize participants is de-scribed below under the TLEQ.

Measures

Traumatic Life Events Questionnaire (TLEQ). The TLEQ(Kubany, 2004) was used to measure traumatic event exposureacross participants’ life span. The TLEQ assesses exposure to 23different traumatic events. For this study, interpersonal traumaitems included: robbed or present during a robbery (item 8); hit orbeaten by a stranger or someone not known very well (item 9);threatened to be killed or caused serious physical harm (item 11);physically punished in a way growing up that resulted in bruises,and so forth (item 12); slapped, punched, kicked or beaten up bya partner (item 14); childhood sexual assault by person at least 5years older (item 15); childhood sexual assault by person approx-imately the same age (item 16); adolescent sexual assault (item17); adult sexual assault (item 18); and stalked (item 19). Itemswere chosen because they represented events in which an individ-ual experienced directly an assault from another person, rather thanevents that had happened to others.

Posttraumatic Stress Diagnostic Scale (PDS). The PDS(Foa, 1995) is a 49-item measure that assesses PTSD symptoms.Participants are asked to identify their worst traumatic event andcomplete questions regarding the event that assess the extent ofnumbing, hypervigilance, and avoidance symptoms in the pastmonth. Two PTSD scores were generated. A PTSD symptom scorewas produced by summing the frequency of PTSD symptoms inthe last month. A PTSD diagnostic cut-off score was generated byfollowing criteria suggested by Coffey et al. (1998), who showedthat a symptom cutoff score of 28 was associated with a sensitivityrate of 89%, a specificity rate of 65% and a correct classificationrate of 74%. According to this criterion, 70% (n � 126) of thesubsample did not qualify for a diagnosis of PTSD and 30% (n �54) did qualify for a diagnosis of PTSD. It is important to remem-ber, however, that those who completed the PDS were only indi-viduals who could identify an upsetting event that has “stuck withthem.” Internal consistency, as reflected by a Cronbach’s alpha,was .92 for the PTSD symptom scale.

Results

Participants reported a range of traumatic experiences and onaverage reported 4.75 (SD � 2.91) traumatic events in theirlifetime. Men and women did not differ in reports of total traumaexposure, t(176) � .30, p � .766. Reports of PTSD symptomsranged from 17 to 55 with a mean of 25.71 (SD � 9.22). Consis-tent with previous research, significant gender disparities in PTSDsymptoms were observed with women reporting overall greaterPTSD symptoms (M � 26.74, SD � 9.68) than men (M � 23.68,SD � 8.16), t(176) � 2.12, p � .035.

As hypothesized, the distribution of men and women across thedifferent IPT groups was skewed. Women were overrepresented inthe life-span IPT group, while men were overrepresented in theadulthood-only group, �2(3) � 14.53, p � .002. More specifically,women comprised 89% of the life-span IPT group (n � 17) despiteonly comprising 65% of the sample, while men comprised 50% of

141INTERPERSONAL TRAUMA AND PTSD

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the adulthood-only group (n � 36). The distribution of genderacross the childhood-only group was as expected.

Consistent with hypotheses, there was a significant differenceacross the IPT groups in regard to PTSD symptoms, F(3, 176) �7.05, p � .001) (Table 1. As predicted, the life-span IPT groupreported the greatest level of PTSD symptoms (M � 34.21, SD �10.58), followed by the childhood-only group (M � 27.00, SD �11.71), adolescent/adulthood-only group (M � 24.84, SD � 8.34),and finally, the no-IPT group (M � 24.13, SD � 7.84). Scheffépost hoc comparisons were used to examine intergroup differ-ences. There were significant differences between the life-spanIPT group and both the adulthood-only IPT group and no-IPTgroup. There was no significant difference between the adolescent/adulthood-only and no-IPT group; however, it is important toremember that the no-IPT group was still exposed to a traumaticevent, though this event was noninterpersonal in nature. Contraryto predictions, there was not a significant difference between thelife-span IPT group and the childhood-only IPT group. Next, wewished to explore whether these groups differed in diagnosticcut-off scores for PTSD. As predicted, a chi-square analysis re-vealed that there was a significant difference between the life-spanIPT group and the childhood-only IPT group such that participantsin the life-span IPT group were overrepresented in the PTSDdiagnostic cut-off score group, �2(1) � 4.56, p � .033.

The fourth hypothesis that IPT-group membership would pre-dict PTSD symptoms after controlling for gender was tested usinga univariate general linear model (GLM). As mentioned previ-ously, men and women significantly differed in their reports ofPTSD symptoms, with women endorsing greater levels of PTSDsymptoms. However, the results of the GLM analysis revealed thatwhen both gender and IPT groups were entered in relationship toPTSD symptoms, only IPT-group membership significantly pre-dicted PTSD symptoms, F � 6.42, p � .001, while the effect ofgender was not significant, F � 2.67, p � .104 (Table 2). Figure 1reveals the average PTSD scores as a function of gender andIPT-group membership.

Discussion

The aims of the present study were to further examine therelationship between gender, IPT exposure, and PTSD symp-toms. Similar to previous authors, gender was implicated in thetypes of IPT to which participants were exposed, as well asreports of PTSD symptoms. More specifically, women wereoverrepresented in the life-span IPT group while men wereoverrepresented in the adolescent/adulthood-only IPT exposuregroup. These results are consistent with previous research thathas shown women to be at greater risk for sexual and physicalabuse in childhood (Breslau, 2001; Flett et al., 2004; McGruderet al., 2000) and suggests that women, perhaps via early vic-timization, may be at heightened risk for revictimization (Cloi-tre et al., 1996; Messman & Long, 1996).

While many explanations have been offered for why womenreport PTSD more frequently than men, research has suggestedthat a significant portion of gender disparities results from anatural extension of qualitative differences in the types oftrauma to which men and women are exposed. The presentstudy contributes to the field by showing that the timing of IPT

Figure 1. Estimated marginal PTSD symptom means as a function ofgender and IPT-group membership.

Table 1Analysis of Variance: Interpersonal Trauma Exposure andPTSD Symptoms Across IPT (N � 180) Groups

Dependentvariable

Cohen’s da

M SD NIPT AIPT CIPT LIPT

IPT exposureNIPT 1.74 4.24 —AIPT 4.69 4.53 .67� —CIPT 6.65 3.93 1.20�� n.s. —LIPT 15.57 9.92 1.81��� 1.41��� 1.18��� —

PTSD symptomsNIPT 24.13 7.84 —AIPT 24.84 8.34 n.s. —CIPT 27.00 11.71 n.s. n.s. —LIPT 34.21 10.58 1.08��� .98�� n.s. —

Note. NIPT � no interpersonal trauma group; AIPT � adolescent/adulthood only interpersonal trauma; CIPT � childhood only interpersonaltrauma; LIPT � lifespan interpersonal trauma.a Cohen’s d presented only for significant mean differences based onScheffe post hoc tests of group differences.� p � .05. �� p � .01. ��� p � .001.

Table 2General Linear Model Predicting PTSD Symptoms (N � 177)

Variable df MS F p �2 Power

IPT Group 3 495.04 6.42 .000��� .10 .97Gender 1 205.68 2.67 .104 .02 .37

Note. �2 � partial eta squared (effect size); Power � observed power todetect effect. Three individuals did not identify their gender, reducing thesample to 177.��� p � .001.

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exposure and revictimization significantly impacts PTSD symp-toms more strongly than gender alone. While participants fol-lowed the typical pattern of gender disparities in PTSD symp-toms (Breslau et al., 1998; Kessler et al., 1995; Koenen &Widom, 2009; Norris et al., 1992; Stein et al., 1997), when bothgender and IPT-group membership were entered in a general linearmodel, only IPT-group membership was significantly (and power-fully) associated with PTSD symptoms, while gender was not. Thisfinding lends continued support to the view that PTSD symptoms maybe more directly related to the types of trauma endured than topretrauma factors such as biological sex.

These results also support previous research that has repeatedlyfound a relationship between early IPT exposure and PTSD (Arata,2000; Brewin, Andrews & Valentine, 2000; Masho & Ahmed, 2007).Like Arata (1999a), when a PTSD diagnostic cut-off score was used,a chi-square analysis showed that the life-span IPT group was over-represented in the PTSD group while those in the childhood-only IPTgroup were overrepresented in the no-PTSD group.

These results may be indicative of something important regard-ing PTSD symptoms versus diagnosis—namely, a certain thresh-old of PTSD symptom endorsement may increase risk for revic-timization, or conversely, continued exposure to IPT increases theseverity of PTSD symptoms that may cross the diagnostic forPTSD. In crossing a cut-off score suggestive of diagnostic thresh-old, it is possible that the individual is experiencing a particularlevel of posttrauma psychopathology that impacts an individual’sability to detect danger and accurately identify signals of risk thatincreases the likelihood for subsequent victimization.

Though the cross-sectional nature of the present study limits theability to determine the direction of effects in regards to IPT andPTSD, the results do offer some preliminary evidence that earlyand subsequent exposure to interpersonal trauma enhances risk forPTSD, and is a better predictor of PTSD than gender. Anotherlimitation is the use of a convenience sample that resulted in morewomen being sampled and unequal subsample sizes per IPT group.Further, the use of an undergraduate sample limits the generaliz-ability of the results. Participants were still rather early in thecourse of their life span, which limits the generalizations that canbe made in regards to individuals in middle and older age groups.It also limited the extent of life-span trauma exposure, which canimpact the presence and/or severity of adverse mental healthoutcomes and artificially decrease the size of membership in thelife-span exposure group. Future research that is prospective orlongitudinal in nature and uses methodology that oversamplesmales is indicated as a result of the current analyses. It is possiblethat factors more frequently endorsed by males, but not included inthis study, such as risk-taking and substance use/abuse (Byrnes,Miller, & Schafer, 1999; Grant et al., 2006), increase adulthoodvictimization rates in males. Finally, the present study did notinclude a control group of participants. Future research that in-cludes a true “no exposure” group may help to elucidate further thedistinctions in mental health between individuals without anytrauma exposure and those with trauma exposure (either noninter-personal, interpersonal, or both).

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Received June 16, 2010Revision received December 7, 2010

Accepted December 15, 2010 �

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