Insecure Attachment History as a Risk Factor for PTSD

Attachment theory and related empirical evidence provide one framework for understanding how maternal PTSD may increase offspring vulnerability to PTSD via effects on the development of self-regulatory abilities. According to attachment theory, the ability to self-regulate arises out of the context of the caregiver–child relationship in the first years of life (Sroufe, Reference Sroufe1995). Initially, neonates and young infants are focused on maintaining physiological homeostasis and rely on their caregivers as regulators (Loman & Gunnar, Reference Loman and Gunnar2010). Physiological stress regulatory systems (e.g., hypothalamic–pituitary–adrenal [HPA] system, autonomic nervous system, central nervous system) become organized during the first months through caregiver–infant transactions, with sensitive caregiving promoting effective stress regulation (Loman & Gunnar, Reference Loman and Gunnar2010). By 4 to 6 months of age, infants become active participants in the regulation of their arousal and emotional states through their relationships with their caregivers (Sroufe, Reference Sroufe1995). By the end of the first year, the attachment relationship is firmly established, and the ability of the relationship to regulate the infant's distress may be observed. During this period, infants begin to show stabilizing patterns of frontal neural activation and predictable behavioral strategies for emotion regulation (Bell & Fox, Reference Bell, Fox, Dawson and Fischer1994; Eisenberg, Spinrad, & Eggum, Reference Eisenberg, Spinrad and Eggum2010). Because of the organizational nature of development, the organization of the dyadic relationship is hierarchically integrated into the self-regulatory system. Thus, disruptions to the attachment relationship may impede the development of optimal self-regulation abilities, and these disruptions may then be carried forward throughout development (Eisenberg et al., Reference Eisenberg, Spinrad and Eggum2010).

Numerous studies have documented associations between the quality of the mother–infant attachment relationship and self-regulation abilities in later life, particularly in the context of stress regulation. Consistently, relationships classified as “secure” compared to relationships classified as “insecure” have been associated with more adaptive self-regulatory abilities and more optimal physiological and behavioral stress regulation (Eisenberg et al., Reference Eisenberg, Spinrad and Eggum2010; Kochanska, Philibet, & Barry, Reference Kochanska, Philibet and Barry2009; Oosterman, De Schipper, Fisher, Dozier, & Schuengel, Reference Oosterman, De Schipper, Fisher, Dozier and Schuengel2010). Moreover, an insecure attachment relationship in infancy has been associated with increased child vulnerability to the effects of contextual risk (Wan & Green, Reference Wan and Green2009).

Maternal PTSD and Insecure Mother–Infant Attachment

Evidence suggests that maternal PTSD may negatively impact the mother–infant relationship. Maternal PTSD symptoms have been associated with greater impairment in mothers' prenatal attachment; distorted, inflexible, negative mental representations of their children; and a range of insensitive caregiving behaviors predictive of insecure attachment (Bar-On et al., Reference Bar-On, Eland, Kleber, Krell, Moore and Sagi1998; Davies, Slade, Wright, & Stewart, Reference Davies, Slade, Wright and Stewart2008; Lyons-Ruth & Block, Reference Lyons-Ruth and Block1996; Muller-Nix et al., Reference Muller-Nix, Forcada-Guex, Pierrehumbert, Jaunin, Borghini and Ansermet2004; Schechter et al., Reference Schechter, Coates, Kaminer, Coots, Zeanah and Davies2008, Reference Schechter, Coots, Zeanah, Davies, Coates and Trabka2005, Reference Schechter, Willheim, Hinojosa, Scholfield-Kleinman, Turner and McCaw2010; Schwerdtfeger & Nelson Goff, Reference Schwerdtfeger and Nelson Goff2007).

The Current Study

The goal of the current study was to examine associations among maternal PTSD, mother–infant attachment, and child and adolescent PTSD using two independent prospective longitudinal data sets. As depicted in Figure 1, each data set was used to test a different component of the conceptual model. Two main hypotheses were tested:

Figure 1. A conceptual model of the mother–infant attachment relationship in the intergenerational transmission of posttraumatic stress disorder (PTSD). Solid circles represent measured constructs, and dotted circles represent unmeasured constructs. D, insecure–disorganized/disoriented.

Hypothesis 1 was tested in an urban, primarily low-income ethnic/racial minority birth cohort sample followed through the first year of life (Study 1). Hypothesis 2 was tested in a low-income, primarily White birth cohort sample assessed during multiple waves of data collection through adolescence (Study 2). In addition, as detailed below within each study's data analysis plan, several alternative hypotheses were tested to support the main hypotheses. The combination of these two studies allows for an examination of the effects of maternal PTSD on the attachment relationship in early development and of the impact of early attachment history on risk for PTSD in later childhood and adolescence.

Study 1

Method

Participants

Participants were mothers and their infants (N = 45 dyads) enrolled in a study of the impact of maternal PTSD on infant physiological, emotional, and behavioral reactivity and regulation. Mothers and infants were recruited from an epidemiological birth-cohort study examining risk factors for asthma development in the Asthma Coalition on Community, Environment, and Social Stress project, an urban, primarily low-income, sample of mixed race/ethnicity (Sternthal et al., Reference Sternthal, Bosquet Enlow, Cohen, Jacobson Canner, Staudenmayer and Tsang2009; Wright et al., Reference Wright, Suglia, Levy, Fortun, Shields and Subramanian2008). Mothers were originally recruited from two major hospitals in Boston and three urban community health centers during their first or second trimester of pregnancy between August 2006 and September 2009. Criteria for inclusion in the current study included (a) mother 18 years or older at child's birth and (b) single gestation birth. Exclusion criteria for the current study included (a) non-English speaking and (b) infants at increased risk for regulatory difficulties due to premature birth (gestational age < 32 weeks), low birth weight (<5.5 lb), congenital abnormalities, or neurological injury (Minde, Reference Minde and Zeanah2000). In addition, during pregnancy, mothers in the parent study were interviewed about alcohol and cigarette use and were not approached for inclusion in the current study if they endorsed usage above established thresholds (≥7 alcoholic drinks/week, smoking ≥10 cigarettes/day; Testa, Quigley, & Eiden, Reference Testa, Quigley and Eiden2003; Wakschlag, Pickett, Cook, Benowitz, & Leventhal, Reference Wakschlag, Pickett, Cook, Benowitz and Leventhal2002).Footnote ¹

The study consisted of two assessments approximately 6.5 months apart. Forty-three mother–infant dyads completed both assessments; an additional two dyads completed the second assessment only but provided data for all of the predictor and outcome measures, allowing them to be included in the analyses. Seven additional dyads completed the first but not second assessment and are missing necessary outcome data to be included in the current study. Data are missing because of infant excessive distress requiring early termination of the protocol (n = 1), inability of the research staff to recontact the dyad (e.g., because of the participant moving, changing phone number, n = 3) or participant refusal to complete the follow-up assessment because of scheduling conflicts or lack of interest (n = 3). There were no differences between dyads who did and did not participate in the second assessment on any of the study predictor variables. Table 1 displays the participant characteristics. All procedures were approved by the relevant institutional review boards, and written informed consent was obtained.

Table 1. Participant demographic characteristics for the entire sample and by PTSD group for Studies 1 and 2

Note: The differences between posttraumatic stress disorder (PTSD) groups in both studies were tested using Fisher's exact tests for categorical variables and t tests for continuous variables. The values in parentheses are standard deviations.

^aIn Study 1, the data for marital status and maternal education were missing for 11.1% and 13.3% of the mothers, respectively. In Study 2, the data for maternal education and for child gestational age and birth weight were missing for 1.0%, 4.2%, and 4.2% of the dyads, respectively.

^bOnly primiparous women were eligible for enrollment in Study 2.

*Significantly different between PTSD groups at p < .05.

Procedures and measures

Mother–infant dyads completed laboratory assessments when the infants were approximately 6 months of age (M = 27.37 weeks, SD = 1.72) and 13 months of age (M = 56.36 weeks, SD = 4.76). Maternal lifetime trauma exposure and psychological symptomatology measures were administered during the 6-month assessment,Footnote ² and a child trauma exposure questionnaire and the mother–infant attachment procedure were administered during the 13-month assessment.

Life Stressor Checklist—Revised (LSC-R)

Maternal lifetime exposure to traumatic events was assessed via interview using the LSC-R (Wolfe & Kimerling, Reference Wolfe, Kimerling, Wilson and Keane1997). The LSC-R assesses exposure and reactions to 30 potentially traumatic events (e.g., experiencing or witnessing a serious accident or natural disaster, childhood maltreatment), including experiences particularly relevant to women (e.g., sexual assault, interpersonal violence). The LSC-R has established reliability and validity in diverse populations (Wolfe & Kimerling, Reference Wolfe, Kimerling, Wilson and Keane1997). A maternal lifetime trauma exposure score (range = 0–30) was derived from the number of endorsed events that met DSM-IV PTSD Criterion A, that is, the events during which the mother reported feeling intense helplessness, fear, and/or horror and thinking that she or someone else could be killed or seriously harmed. Mothers were categorized as to whether they had experienced “no trauma exposure” (no events), “low trauma exposure” (one to two events), or “high trauma exposure” (three or more events) during their lifetime.

Posttraumatic Stress Disorder Checklist—Civilian Version (PCL-C)

PTSD symptomatology was assessed via interview using the PCL-C (Weathers, Huska, & Keane, Reference Weathers, Huska and Keane1991), a 17-item measure that reflects DSM-IV symptom criteria for PTSD. Mothers rated each symptom on a 5-point Likert scale in terms of how much it had bothered them in the prior month. Responses can be used to determine whether participants likely meet DSM-IV criteria for PTSD. Specifically, participants who endorsed being moderately to extremely bothered by one or more reexperiencing symptoms (Cluster B), three or more avoidance/numbing symptoms (Cluster C), and two or more hyperarousal symptoms (Cluster D) were classified into an “elevated” PTSD symptoms group, likely meeting DSM-IV criteria for PTSD. Participants who did not meet these criteria were classified into a “nonelevated” PTSD symptoms group. The PCL-C has good test–retest reliability and convergent validity with a number of other PTSD scales and with the Clinician-Administered PTSD Scale, a structured clinical interview for PTSD (Brewin, Reference Brewin2005; Weathers, Keane, & Davidson, Reference Weathers, Keane and Davidson2001). Internal consistency in this sample was high (Cronbach α = 0.94).

Edinburgh Postnatal Depression Scale (EPDS)

Maternal depressive symptoms during the prior week were assessed via interview using the 10-item EPDS (Cox, Holden, & Sagovksy, Reference Cox, Holden and Sagovksy1987), a measure specifically designed to address depressive symptoms in the postnatal period. Participants who scored 13 or greater were classified into an “elevated” depressive symptoms group; the remainder were classified into a “nonelevated” depressive symptoms group. The measure has been validated in childbearing women and has demonstrated high internal consistency and validity for detecting major depression in the perinatal period with a cutoff score of 13 (Cox, Chapman, Murray, & Jones, Reference Cox, Chapman, Murray and Jones1996). Internal consistency in this sample was high (Cronbach α = 0.91).

Traumatic Events Screening Inventory—Parent Report Revised (TESI-PRR)

Infant lifetime exposure to potentially traumatic events was assessed via maternal report using the TESI-PRR (Ghosh Ippen et al., Reference Ghosh Ippen, Ford, Racusin, Acker, Bosquet and Rogers2002), an interview measure specifically developed for children ages 0–6 to screen for a wide range of potentially traumatic events (e.g., accidents, abuse and neglect, witnessing family violence, separation from primary caregiver, attack by an animal; Stover & Berkowitz, Reference Stover and Berkowitz2005). The TESI-PRR is a modification of the TESI-PR, which has demonstrated good psychometric properties (Ford et al., Reference Ford, Racusin, Ellis, Daviss, Reiser and Fleischer2000). A trauma exposure score was calculated by summing the number of events to which the infant was exposed. Infants were categorized as to whether they had experienced “no exposure to potentially traumatic events” (no events), “low exposure” (one event), or “high exposure” (two or more events) during their lifetime.

Strange Situation Procedure (SSP)

The SSP (Ainsworth et al., Reference Ainsworth, Blehar, Waters and Wall1978) was administered to assess the quality of the mother–infant attachment relationship. The standardized laboratory procedure consists of eight brief episodes designed to activate infant attachment behaviors via increasingly stressful mother–infant separations and reunions. The procedures were videotaped to enable scoring of attachment classification based on the infants' use of the mother as a secure base from which to explore and as a source of comfort when distressed. Mother–infant dyads were scored into one of the three major classifications: secure, insecure–avoidant, or insecure–resistant. Dyads were separately coded for the presence/absence of insecure–disorganized/disoriented attachment using the classification scheme developed by Main and Solomon (Reference Main, Solomon, Greenberg, Cicchetti and Cummings1990). Disorganization/disorientation behaviors were rated on a 9-point scale; dyads scoring 5 or higher were coded as meeting criteria for an insecure–disorganized/disoriented classification. An internationally recognized expert in attachment coding (third author), who was blind to the other study data, coded the assessments for insecure–avoidant/secure/insecure–resistant and for insecure–disorganized/disoriented. A second coder also blind to the other study data rated 25% of the assessments; the two coders achieved 80% agreement on attachment classifications. For the current analyses, three dichotomous yes/no scores were used: whether the dyad met criteria for one of the major insecure classifications (insecure–avoidant or insecure–resistant vs. secure, regardless of insecure–disorganized/disoriented status), whether the dyad met criteria for an insecure–disorganized/disoriented classification (insecure–disorganized/disoriented or not insecure–disorganized/disoriented), and whether the dyad met criteria for any insecure classification (insecure–avoidant, insecure–resistant, and/or insecure–disorganized/disoriented vs. secure without insecure–disorganized/disoriented).

Demographic risk factors

Demographic risk factors assessed include maternal age, marital status, education level, and parity at the child's birth; maternal and child race/ethnicity; and child gender, gestational age, and birth weight. Marital status was dichotomized into married or not married (single, separated, divorced, widowed). Maternal educational attainment was split into three categories: did not graduate high school/obtain GED, graduated high school/obtained GED, attended at least some college/associate's degree. Parity was dichotomized into primiparous or multiparous. Maternal age (years) and child gestational age (weeks) and birth weight (g) were treated as continuous variables.

Study 2

General Discussion

Evidence suggests that offspring of parents with PTSD are at increased risk of developing PTSD during their lifetime (Baranowsky, Young, Johnson-Douglas, Williams-Keeler, & McCarrey, Reference Baranowsky, Young, Johnson-Douglas, Williams-Keeler and McCarrey1998; Roberts et al., Reference Roberts, Galea, Austin, Cerda, Wright and Rich-Edwards2012; Yehuda, Halligan, & Bierer, Reference Yehuda, Halligan and Bierer2001; Yehuda, Schmeidler, Giller et al., Reference Yehuda, Schmeidler, Giller, Siever and Binder-Brynes1998; Yehuda, Schmeidler, Wainberg et al., Reference Yehuda, Schmeidler, Wainberg, Binder-Brynes and Duvdevani1998). The mechanisms responsible for this intergenerational transmission are poorly understood. The goal of the current study was to test whether the quality of the mother–infant attachment relationship may contribute to the association between maternal and offspring PTSD (Figure 1). Two longitudinal studies were used to test two main hypotheses: (a) maternal PTSD increases risk for the development of an insecure, particularly insecure–disorganized/disoriented, mother–infant attachment relationship. (b) A history of an insecure, particularly insecure–disorganized/disoriented, mother–infant attachment relationship increases a child's vulnerability to developing PTSD in response to later trauma exposure. The results provided some support for both hypotheses, demonstrating significant associations between maternal PTSD and insecure, particularly insecure–disorganized/disoriented, mother–infant attachment and between insecure (insecure–avoidant or insecure–resistant) mother–infant attachment history and lifetime risk of PTSD by adolescence. Contrary to our a priori hypothesis, insecure–disorganized/disoriented attachment in infancy was not predictive of later PTSD diagnosis. However, insecure–disorganized/disoriented attachment history was predictive of severity of PTSD symptoms at 17.5 years. Together, the findings suggest that (a) maternal PTSD may increase risk of child and adolescent PTSD through its effects on the quality of the mother–infant attachment relationship and (b) a history of an insecure mother–infant attachment relationship has persistent effects on an individual's vulnerability to developing PTSD in later life.

Associations between maternal PTSD and mother–infant attachment were tested in an urban, primarily low-income, racial/ethnic minority community-based birth cohort followed longitudinally through the children's first year of life (Study 1). The results demonstrated that infants of mothers with elevated PTSD symptoms when the infants were age 6 months were at 4.77 and 13.17 times greater risk of developing an insecure–avoidant or insecure–resistant and an insecure–disorganized/disoriented attachment relationship, respectively, by 13 months of age. Among dyads in the elevated maternal PTSD symptoms group, 66.6% were classified as insecure–avoidant or insecure–resistant and 58.3% as insecure–disorganized/disoriented; almost the entire group, 83.3%, was classified as insecure–avoidant, insecure–resistant, and/or insecure–disorganized/disoriented. These rates are notably higher than those found in prior research (e.g., 24% insecure–avoidant or insecure–resistant in typical middle-class North American populations; 30%–45% insecure–disorganized/disoriented in clinical and low SES populations; van IJzendoorn et al., Reference van IJzendoorn, Schuengel and Bakermans-Kranenburg1999), suggesting potent effects of PTSD on the mother–infant attachment relationship.

In a second urban, low-income, primarily White community-based birth cohort (Study 2), analyses examined whether a history of insecure attachment in infancy predicted greater vulnerability to the development of PTSD in childhood or adolescence following trauma exposure. The results demonstrated a significant, dose–response relationship between an insecure (insecure–avoidant or insecure–resistant) attachment in infancy and a PTSD diagnosis by 17.5 years of age, with those insecurely attached at both 12 and 18 months at greatest risk and those securely attached at both time points at lowest risk. Contrary to expectation, a history of insecure–disorganized/disoriented attachment was not associated with increased lifetime risk for a diagnosis of PTSD; however, a history of insecure–disorganized/disoriented attachment was predictive of more severe PTSD symptoms at 17.5 years of age.

The findings associating insecure–disorganized/disoriented attachment history with PTSD symptom severity in adolescence but not lifetime diagnosis may reflect a nuanced relationship between insecure–disorganized/disoriented attachment history and PTSD. The theories that have purported an increased risk of PTSD among individuals with a history of insecure–disorganized/disoriented attachment have largely relied on the potential role of insecure–disorganized/disoriented attachment history in dissociative processes (Liotti Reference Liotti1992, Reference Liotti2004; Schore, Reference Schore2002). Research supports subtypes of PTSD among both children and adults that are characterized by different neurobiological profiles and patterns of emotional dysregulation, with one rarer type consisting of dissociative symptoms and emotional overmodulation and another more common type consisting primarily of hyperarousal, reexperiencing symptoms, and emotional undermodulation (Lanius et al., Reference Lanius, Vermetten, Loewenstein, Brand, Schmahl and Bremner2010; Lanius, Brand, Vermetten, Frewen, & Spiegel, Reference Lanius, Brand, Vermetten, Frewen and Spiegel2012; Stein et al., Reference Stein, Koenen, Friedman, Hill, McLaughlin and Petukhova2012). A history of insecure–disorganized/disoriented attachment possibly increases risk for trauma-induced psychopathology with strong dissociative features (e.g., dissociative subtypes of PTSD, dissociative disorders, borderline personality disorder) but not for trauma-induced psychopathology without dissociative features, including subtypes of PTSD with minimal dissociative symptoms. Of note, two other studies using the MLSRA cohort found that insecure–disorganized/disoriented attachment in infancy was predictive of childhood and adolescent dissociative symptoms (Carlson, Reference Carlson1998; Ogawa et al., Reference Ogawa, Sroufe, Weinfield, Carlson and Egeland1997). Because these studies did not require that participants report trauma exposure to be included in analyses, they were able to utilize larger samples (Carlson, N = 157; Ogawa et al., N = 168), which provided greater power to detect effects. Associations between insecure–disorganized/disoriented attachment history and PTSD may also depend on the nature and the timing of the trauma exposure that induced PTSD. For example, insecure–disorganized/disoriented may be more likely to predict PTSD in individuals exposed to chronic and severe trauma early in life than in individuals exposed to an acute trauma or to trauma later in life, as early-onset exposure to multiple traumas is more likely to lead to dissociative symptoms (Lanius et al., Reference Lanius, Vermetten, Loewenstein, Brand, Schmahl and Bremner2010, Reference Lanius, Brand, Vermetten, Frewen and Spiegel2012; Stein et al., Reference Stein, Koenen, Friedman, Hill, McLaughlin and Petukhova2012). Finally, the pattern of findings suggests that the overarching attachment history (secure vs. insecure–avoidant or insecure–resistant) may contribute to whether or not an individual develops PTSD following trauma exposure, and an insecure–disorganized/disoriented attachment history may influence the course of PTSD symptoms, including severity and perhaps also type and duration. Recent research suggests that distinct processes are involved in peritraumatic versus persistent dissociative reactions following trauma exposure, with the latter predictive of greater severity and persistence of PTSD symptoms (Werner & Griffin, Reference Werner and Griffin2012). Similarly, the dissociative subtype of PTSD has been associated with more severe and impairing forms of PTSD and with the persistence of dissociative symptoms even after other PTSD symptoms have resolved (Lanius et al., Reference Lanius, Vermetten, Loewenstein, Brand, Schmahl and Bremner2010; Stein et al., Reference Stein, Koenen, Friedman, Hill, McLaughlin and Petukhova2012). Thus, an insecure–disorganized/disoriented attachment history may contribute to the severity and course of PTSD by increasing the likelihood of persistent dissociative reactions. Further research is needed to determine how any of these factors may influence associations between attachment history and later PTSD.

Given a large body of research showing gender differences in the prevalence and presentation of PTSD for reasons that are poorly understood (Pratchett et al., Reference Pratchett, Pelcovitz and Yehuda2010), Study 2 analyses examined the role of gender in the prediction of lifetime trauma exposure and PTSD and as a moderator of the relationship between mother–infant attachment history and PTSD. Consistent with prior studies of adolescents (Cuffe et al., Reference Cuffe, Addy, Garrison, Waller, Jackson and McKeown1998; Pratchett et al., Reference Pratchett, Pelcovitz and Yehuda2010; Seedat et al., Reference Seedat, Stein and Carey2005), females reported greater trauma exposure than males (64.6% vs. 46.2%), and females were more likely than males (35.8% vs. 14.0%) to meet diagnostic criteria for PTSD following trauma exposure. There was no evidence that a history of insecure attachment functioned differently as a risk factor for the development of PTSD among trauma-exposed males and females.

Analyses explored whether differential rates of trauma exposure may have accounted for the significant associations between attachment and PTSD in the two studies. Previous research suggests that offspring of trauma-exposed parents, particularly parents with PTSD, experience traumatic events at higher rates than offspring of non-trauma-exposed/PTSD-affected parents (Copeland et al., Reference Copeland, Keeler, Angold and Costello2007; Cuevas et al., Reference Cuevas, Finkelhor, Ormrod and Turner2009; Yehuda, Halligan, & Grossman, Reference Yehuda, Halligan and Grossman2001) and that this increased trauma exposure accounts for elevated rates of PTSD among offspring of mothers with PTSD (Roberts et al., Reference Roberts, Galea, Austin, Cerda, Wright and Rich-Edwards2012). Moreover, trauma exposure in early development increases the probability of an insecure, particularly insecure–disorganized/disoriented, attachment relationship (Baer & Martinez, Reference Baer and Martinez2006; Sroufe et al., Reference Sroufe, Egeland, Carlson and Collins2005; Zeanah et al., Reference Zeanah, Danis, Hirshberg, Benoit, Miller and Heller1999). In Study 1, infant trauma exposure was not associated with either maternal PTSD status or attachment classification, and controlling for infant trauma exposure did not affect the magnitudes of association between maternal PTSD and mother–infant insecure or insecure–disorganized/disoriented attachment. Study 2 failed to find an association between attachment history and later trauma exposure. Moreover, the analyses demonstrating significant associations between attachment history and PTSD were limited to participants who reported prior trauma exposure. Thus, the significant associations between attachment history and PTSD were not attributable to higher rates of trauma exposure among infants of mothers with PTSD in Study 1 or among children/adolescents with insecure attachment histories in Study 2.

Study 1 analyses tested whether the associations between maternal PTSD and mother–infant attachment were due to the effects of depression, which is highly comorbid with PTSD (Chemtob et al., Reference Chemtob, Nomura, Rajendran, Yehuda, Schwartz and Abramovitz2010; O'Campo et al., Reference O'Campo, Kub, Woods, Garza, Jones and Gielen2006). Previous studies have documented elevated rates of insecure attachment among depressed mothers and their infants (Atkinson et al., Reference Atkinson, Paglia, Coolbear, Niccols, Parker and Guger2000; Martins & Gaffan, Reference Martins and Gaffan2000). In Study 1, mother–infant attachment was associated with maternal PTSD but not maternal depressive symptoms. Of note, studies that have examined associations between maternal depression and mother–infant attachment have reported inconsistent results, with meta-analyses suggesting that the associations are modest (Atkinson et al., Reference Atkinson, Paglia, Coolbear, Niccols, Parker and Guger2000; Tharner et al., Reference Tharner, Luijk, van IJzendoorn, Bakermans-Kranenburg, Jaddoe and Hofman2012; van IJzendoorn et al., Reference van IJzendoorn, Schuengel and Bakermans-Kranenburg1999). Heterogeneity in maternal depression effects may be attributable to differences in severity of illness and the presence of additional psychiatric disorders and other risk factors across samples (Carter, Garrity-Rokous, Chazan-Cohen, Little, & Briggs-Gowan, Reference Carter, Garrity-Rokous, Chazan-Cohen, Little and Briggs-Gowan2001; Toth, Rogosch, Sturge-Apple, & Cicchetti, Reference Toth, Rogosch, Sturge-Apple and Cicchetti2009). There is some evidence that maternal depression in the absence of comorbid psychiatric diagnoses or life adversity (e.g., poverty, dangerous environments) confers limited increased risk to the mother–infant relationship (Carter et al., Reference Carter, Garrity-Rokous, Chazan-Cohen, Little and Briggs-Gowan2001; Tharner et al., Reference Tharner, Luijk, van IJzendoorn, Bakermans-Kranenburg, Jaddoe and Hofman2012). Generally, studies documenting associations between maternal depression and mother–infant attachment have not assessed maternal trauma history or PTSD, though many of these studies have been conducted with populations at heightened risk for trauma exposure (e.g., urban, low-income). Given the high comorbidity commonly found between PTSD and depression, particularly in perinatal women (Loveland Cook et al., Reference Loveland Cook, Flick, Homan, Campbell, McSweeney and Gallagher2004), the positive depression–attachment findings that have been reported in the literature may be attributable, at least in part, to the effects of PTSD, particularly in populations with high rates of trauma exposure.

Several mechanisms may be responsible for disrupting the attachment relationships of mothers with PTSD and their infants. PTSD is associated with serious disturbances in physiological, emotional, and behavioral self-regulation, and self-regulation is fundamental to forming and maintaining a healthy parent–child relationship (Hien, Cohen, & Campbell, Reference Hien, Cohen and Campbell2005; Schechter & Willheim, Reference Schechter and Willheim2009; Schechter et al., Reference Schechter, Zeanah, Myers, Brunelli, Liebowitz and Marshall2004, Reference Schechter, Moser, Wang, Marsh, Hao and Duan2011). Self-regulation difficulties likely impede PTSD-affected mothers' abilities to recognize their infants' cues and respond sensitively and, consequently, foster a secure attachment relationship (Schechter & Willheim, Reference Schechter and Willheim2009). Maternal trauma exposure and PTSD have been associated with a range of insensitive caregiving behaviors, including increased intrusiveness and hostility, overprotectiveness, restricted affect, emotional withdrawal, frightened/frightening behaviors, and emotional and physical neglect (Bar-On et al., Reference Bar-On, Eland, Kleber, Krell, Moore and Sagi1998; Goldberg, Benoit, Blokland, & Madigan, Reference Goldberg, Benoit, Blokland and Madigan2003; Jacobvitz, Leon, & Hazen, Reference Jacobvitz, Leon and Hazen2006; Lyons-Ruth & Block, Reference Lyons-Ruth and Block1996; Muller-Nix et al., Reference Muller-Nix, Forcada-Guex, Pierrehumbert, Jaunin, Borghini and Ansermet2004; Schechter et al., Reference Schechter, Coates, Kaminer, Coots, Zeanah and Davies2008, Reference Schechter, Willheim, Hinojosa, Scholfield-Kleinman, Turner and McCaw2010; Yehuda & Bierer, Reference Yehuda and Bierer2008; Yehuda, Halligan, & Grossman, Reference Yehuda, Halligan and Grossman2001). Mothers with different subtypes of PTSD may exhibit different patterns of caregiving. For example, the subtype of PTSD characterized by dissociative symptoms may be associated with withdrawal, emotional unavailability, and dissociative episodes, whereas the subtype characterized by hyperarousal and reexperiencing symptoms may be associated with intrusive, angry, irritable behaviors. Different parenting behaviors may in turn be associated with different patterns of attachment (e.g., withdrawn → insecure–resistant attachment; hostile → insecure–avoidant attachment). Some of the characteristic symptoms of PTSD, such as flashbacks, emotional numbing, angry outbursts, and hypervigilance, may be especially likely to increase the probability that a mother will exhibit the anomalous behaviors that increase risk of an insecure–disorganized/disoriented attachment relationship, including disorientation, dissociative episodes, nonresponsiveness, frightening and hostile behaviors, and frightened facial expressions. Caregiving behaviors may be further compromised by the use of alcohol and/or drugs, as research has documented that PTSD-affected women are at heightened risk for abusing substances to ameliorate their PTSD symptoms (Chilcoat & Breslau, Reference Chilcoat and Breslau1998; Hien et al., Reference Hien, Jiang, Campbell, Hu, Miele and Cohen2010).

An insecure mother–infant attachment relationship that results from repeated exposures to such insensitive caregiving behaviors may then increase the child's PTSD vulnerability by permanently programming the epigenetic expression of genes involved in the physiological stress response, shaping nonoptimal neurological patterns of stress reactivity, and establishing maladaptive emotional and behavioral styles of coping in response to challenge (McGowan et al., Reference McGowan, Suderman, Sasaki, Huang, Hallett and Meaney2011; Nolte, Guiney, Fonagy, Mayes, & Luyten, Reference Nolte, Guiney, Fonagy, Mayes and Luyten2011; Schore, Reference Schore2002; Weaver, Meaney, & Szyf, Reference Weaver, Meaney and Szyf2006). For example, early caregiving quality has been shown to play a critical role in the programming of the functioning of the HPA axis, with secure attachment predicting more optimal regulation under stress conditions (Gunnar & Quevedo, Reference Gunnar and Quevedo2007, Reference Gunnar and Quevedo2008). Moreover, alterations in the normal functioning of the HPA axis have been implicated in increased risk for later psychopathology, including PTSD (Gunnar & Quevedo, Reference Gunnar and Quevedo2008; McFarlane, Barton, Yehuda, & Wittert, Reference McFarlane, Barton, Yehuda and Wittert2011). Nolte and colleagues have suggested that early caregiving experiences influence the neural circuitry of core regions of the brain involved in stress responding such that individuals with an insecure attachment history underrecruit prefrontal brain regions involved in stress regulation and are vulnerable to amygdala hyperactivation. Dysfunctional activity in both the prefrontal cortex and the amygdala have been implicated in PTSD (Aupperle et al., Reference Aupperle, Allard, Grimes, Simmons, Flagan and Behrooznia2012; Etkin & Wagner, Reference Etkin and Wagner2007; Garrett et al., Reference Garrett, Carrion, Kletter, Karchemskiy, Weems and Reiss2012). In addition, mothers with PTSD may model numerous behaviors that may increase child risk for PTSD, including fearful affect, hypervigilance, attentional bias to threat, catastrophic interpretations of events, avoidant coping strategies, and poor self-regulation in stressful situations (Nolte et al., Reference Nolte, Guiney, Fonagy, Mayes and Luyten2011).

Internal working models (IWMs) may be involved in associations between maternal PTSD and mother–infant attachment and between attachment history and PTSD. IWMs are conceptualized as emotional, motivational, and cognitive knowledge or representations that shape how the individual views him/herself, others, and the world (Liotti, Reference Liotti2004; Spangler & Zimmermann, Reference Spangler and Zimmermann1999). The specific characteristics of an individual's IWMs are hypothesized to emerge from the quality of early caregiver–child interactions and to have moderate stability over time into adulthood (Carlson, Sroufe, & Egeland, Reference Carlson, Sroufe and Egeland2004; Fraley, Reference Fraley2002; Ranson & Urichuk, Reference Ranson and Urichuk2008). IWMs may have particular influence over individuals' physiological and emotional regulation and interpersonal functioning under stress conditions (Nolte et al., Reference Nolte, Guiney, Fonagy, Mayes and Luyten2011; Spangler & Schieche, Reference Spangler and Schieche1998; Spangler & Zimmermann, Reference Spangler and Zimmermann1999).

Maternal PTSD has been associated with insecure maternal IWMs, including unresolved states of mind with respect to loss or trauma in childhood and nonbalanced, distorted representations of their own child (Bakermans-Kranenburg & van IJzendoorn, Reference Bakermans-Kranenburg and van IJzendoorn2009; Lieberman, Reference Lieberman1999; Schechter et al., Reference Schechter, Coots, Zeanah, Davies, Coates and Trabka2005, Reference Schechter, Zygmunt, Coates, Davies, Trabka and McCaw2007), both of which have been linked to caregiving behaviors that predict insecure, and particularly insecure–disorganized/disoriented, mother–infant attachment relationships (e.g., hostile–intrusiveness/negativity, disoriented/frightening behaviors; Schechter et al., Reference Schechter, Coates, Kaminer, Coots, Zeanah and Davies2008). Insecure maternal IWMs have also been associated with lower levels of reflective functioning or mentalization, that is, the ability to conceive of the self and others as social agents whose thoughts, feelings, desires, and behaviors are driven by intentional mental states (Fonagy, Gergely, Jurist, & Target, Reference Fonagy, Gergely, Jurist and Target2002; Schechter et al., Reference Schechter, Coots, Zeanah, Davies, Coates and Trabka2005; Schechter & Willheim, Reference Schechter and Willheim2009; Slade, Grienenberger, Bernbach, Levy, & Locker, Reference Slade, Grienenberger, Bernbach, Levy and Locker2005). Lower levels of maternal reflective functioning have been found to predict more negative caregiving behaviors, insecure mother–infant attachment, and lower levels of child reflective functioning (Nolte et al., Reference Nolte, Guiney, Fonagy, Mayes and Luyten2011; Grienenberger, Kelly, & Slade, Reference Grienenberger, Kelly and Slade2005; Schechter et al., Reference Schechter, Coots, Zeanah, Davies, Coates and Trabka2005; Slade et al., Reference Slade, Grienenberger, Bernbach, Levy and Locker2005). Although there have been theoretical arguments for hypothesizing lower levels of reflective functioning abilities among mothers with PTSD, the limited research has not found such a link (Schechter et al., Reference Schechter, Coots, Zeanah, Davies, Coates and Trabka2005). More research in this area is warranted.

The negative types of IWM representations about the self, others, and the world that arise out of an insecure mother–infant attachment relationship have been hypothesized to increase risk for PTSD (Sandberg, Suess, & Heaton, Reference Sandberg, Suess and Heaton2010). The IWMs associated with insecure attachment histories are characterized by views of the self as helpless, vulnerable, or unlovable, others as unreliable, helpless, or malevolent, and the world as threatening or dangerous (Liotti, Reference Liotti1992, Reference Liotti2004; Sandberg et al., Reference Sandberg, Suess and Heaton2010). Representations of the self as vulnerable and helpless and the world as dangerous may increase hypervigilance, distrust, and intrusive recollections following a traumatic event (Sandberg et al., Reference Sandberg, Suess and Heaton2010). Feelings of guilt and shame associated with negative representations of the self may interfere with the ability to regulate affect and cope with painful emotions (Sandberg et al., Reference Sandberg, Suess and Heaton2010). The inability to process negative emotional experiences may lead to avoidance, which can interfere with recovery (Sandberg et al., Reference Sandberg, Suess and Heaton2010). Mental representations of others as rejecting, inconsistent, or traumatizing may influence perceptions of social support and willingness to seek out and accept support (Sandberg et al., Reference Sandberg, Suess and Heaton2010). Of note, insecure IWMs are remarkably similar to the types of cognitive schemas that have been associated with PTSD (Elwood & Williams, Reference Elwood and Williams2007; Foa, Ehlers, Clark, Tolin, & Orsillo, Reference Foa, Ehlers, Clark, Tolin and Orsillo1999; Liotti, Reference Liotti1992, Reference Liotti2004; Sandberg et al., Reference Sandberg, Suess and Heaton2010; Yehuda, Halligan, & Grossman, Reference Yehuda, Halligan and Grossman2001). Although no research has specifically examined how IWMs that arise out of the mother–infant attachment relationship influence PTSD risk, findings from numerous adult studies support the hypothesis that attachment style mediates or moderates the relation between trauma exposure and PTSD (Benoit et al., Reference Benoit, Bouthillier, Moss, Rousseau and Brunet2010; Besser & Neria, Reference Besser and Neria2012; Dieperink, Leskela, Thuras, & Engdahl, Reference Dieperink, Leskela, Thuras and Engdahl2001; Elwood & Williams, Reference Elwood and Williams2007; Fraley, Fazzari, Bonanno, & Dekel, Reference Fraley, Fazzari, Bonanno and Dekel2006; Muller, Sicoli, & Lemieux, Reference Muller, Sicoli and Lemieux2000; O'Connor & Elklit, Reference O'Connor and Elklit2008; Sandberg et al., Reference Sandberg, Suess and Heaton2010; Scott & Babcock, Reference Scott and Babcock2010; Stovall-McClough & Cloitre, Reference Stovall-McClough and Cloitre2006). Moreover, maternal PTSD symptoms have been found to predict child IWM characteristics that parallel PTSD symptoms, including attentional bias to danger and distress and avoidance of and withdrawal from conflicts (Schechter et al., Reference Schechter, Zygmunt, Coates, Davies, Trabka and McCaw2007). Thus, the IWMs of both the mother and the child may play critical roles in the intergenerational transmission of PTSD (Lieberman, Reference Lieberman1999).

Genetic factors may also play a role in associations between mother–infant attachment and PTSD. For example, there is evidence that maternal unresolved loss or trauma and disrupted maternal affective communication are predictors of insecure–disorganized/disoriented mother–infant attachment among infants with a specific polymorphism of the dopamine receptor D4 (DRD4) gene, suggesting that infants' sensitivity to caregiving quality is modulated by genetic factors (Gervai et al., Reference Gervai, Novak, Lakatos, Toth, Danis and Ronai2007; van IJzendoorn & Bakermans-Kranenburg, Reference van IJzendoorn and Bakermans-Kranenburg2006). Moreover, there is limited evidence that variations in the DRD4 gene are differentially associated with likelihood of unresolved status in response to negative childhood experiences (Bakermans-Kranenburg, van IJzendoorn, Caspers, & Philibert, Reference Bakermans-Kranenburg, van IJzendoorn, Caspers and Philibert2011) and with severity of PTSD symptoms among trauma survivors (Dragan & Oniszczenko, Reference Dragan and Oniszczenko2009). Similarly, the catechol-O-methyltransferase Val158Met polymorphism has been associated with insecure–disorganized/disoriented attachment (Luijk et al., Reference Luijk, Roisman, Haltigan, Tiemeier, Booth-Laforce and van IJzendoorn2011) and with PTSD (Valente et al., Reference Valente, Vallada, Cordeiro, Bressan, Andreoli and Mari2011), possibly by influencing carriers' susceptibility to environmental influences and/or emotional arousal and stress regulatory abilities. Certain genetically based temperamental characteristics, such as behavioral inhibition, may also increase risk for insecure attachment, particularly among infants of anxious mothers, and for PTSD (Myers, VanMeenen, & Servatius, Reference Myers, VanMeenen and Servatius2012; Stevenson-Hinde, Shouldice, & Chicot, Reference Stevenson-Hinde, Shouldice and Chicot2011). Therefore, there may be multiple genetic polymorphisms that increase risk for both an insecure attachment relationship and for PTSD, particularly under negative environmental conditions.

Finally, maternal PTSD may impact the mother–infant attachment relationship and offspring PTSD vulnerability through contextual risk factors. For example, mothers with PTSD may be at greater risk for experiencing disruptive events, such as job loss, divorce, and exposure to chronic adversities and traumas (Chiu, deRoon-Cassini, & Brasel, Reference Chiu, deRoon-Cassini and Brasel2011; Roberts et al., Reference Roberts, Galea, Austin, Cerda, Wright and Rich-Edwards2012). PTSD has also been associated with depressed IQ, lower socioeconomic achievement, and diminished social support (Chiu et al., Reference Chiu, deRoon-Cassini and Brasel2011; De Bellis, Hooper, Spratt, & Woolley, Reference De Bellis, Hooper, Spratt and Woolley2009). The presence of these risk factors may negatively impact caregiving behaviors, increase maternal and child exposures to stress and trauma, and diminish supportive buffers in the child's environment, all increasing risk for an insecure attachment relationship and child and adolescent PTSD (Levendosky, Bogat, Huth-Bocks, Rosenblum, & von Eye, Reference Levendosky, Bogat, Huth-Bocks, Rosenblum and von Eye2011; Levendosky, Leahy, Bogat, Davidson, & von Eye, Reference Levendosky, Leahy, Bogat, Davidson and von Eye2006; Nolte et al., Reference Nolte, Guiney, Fonagy, Mayes and Luyten2011; Roberts et al., Reference Roberts, Galea, Austin, Cerda, Wright and Rich-Edwards2012). The current analyses did not provide evidence that the significant associations were attributable to contextual risk factors. Specifically, in Study 1, associations between maternal PTSD symptoms and mother–infant attachment could not be attributed to maternal age, marital status, education, race/ethnicity, or parity, or child race/ethnicity, gender, gestational age, or birth weight. In Study 2, PTSD diagnosis was not predicted by maternal age, marital status, or education at the time of the child's birth, maternal or child race, child gestational age, birth weight, or IQ, SES or life stress through adolescence, or quality of the mother–child dyadic relationship in later childhood or adolescence. However, unmeasured contextual risk factors may have contributed to the significant associations. Contextual risk factors may also moderate associations. For example, maternal PTSD may be most likely to disrupt caregiving and the mother–infant attachment relationship when the mother has few cognitive, emotional, and financial resources available. Similarly, an insecure mother–infant attachment history may have a more substantial impact on PTSD vulnerability among children and adolescents living in chaotic environments with fewer alternative supportive adults.

The high rates of trauma exposure and PTSD found in Studies 1 and 2 reflect population prevalence rates, particularly in urban, low-income groups (Copeland et al., Reference Copeland, Keeler, Angold and Costello2007; Ford, Elhai, Ruggiero, & Frueh, Reference Ford, Elhai, Ruggiero and Frueh2009; Gillespie et al., Reference Gillespie, Bradley, Mercer, Smith, Conneely and Gapen2009; Kessler et al., Reference Kessler, Sonnega, Bromet, Hughes and Nelson1995; Parto et al., Reference Parto, Evans and Zonderman2011; Roberts et al., Reference Roberts, Gilman, Breslau, Breslau and Koenen2011; Seng et al., Reference Seng, Kane Low, Sperlich, Ronis and Liberzon2009). These data highlight the public health importance of determining the etiology of PTSD and the processes involved in the intergenerational transmission of PTSD so that appropriate prevention and intervention strategies may be developed. An examination of the timing and type of traumatic exposures that the mothers in Study 1 experienced revealed that the majority occurred years before the child's conception and varied across type, including interpersonal (e.g., abuse, neglect) and noninterpersonal (e.g., accidents) events. To date, much of the research documenting the effects of maternal trauma on child and parenting outcomes has focused on prenatal or postnatal exposures. Furthermore, studies that have considered lifetime trauma exposures have focused almost exclusively on interpersonal traumas, particularly a history of childhood maltreatment, because of theories that such experiences engender specific vulnerabilities that interfere with the ability to provide sensitive caregiving (Fraiberg, Adelson, & Shapiro, Reference Fraiberg, Adelson and Shapiro1975; Schechter et al., Reference Schechter, Coates, Kaminer, Coots, Zeanah and Davies2008; Schwerdtfeger & Nelson Goff, Reference Schwerdtfeger and Nelson Goff2007). If trauma exposures influence the attachment relationship via the disruptive effects of PTSD symptomatology on maternal caregiving behaviors, then any type of trauma that occurs at any point in the mother's life and leads to PTSD may increase the likelihood of an insecure attachment relationship. However, certain trauma histories may present more extreme challenges to the mother–infant relationship among mothers with PTSD, further increasing the likelihood of an insecure attachment relationship. For example, normative displays of infant helplessness, distress, and aggression may be especially threatening and triggering for mothers with PTSD resulting from intimate partner violence, particularly if the infant physically resembles the perpetrator (Schechter et al., Reference Schechter, Coates, Kaminer, Coots, Zeanah and Davies2008, Reference Schechter, Willheim, Hinojosa, Scholfield-Kleinman, Turner and McCaw2010). The mother may respond by emotionally and physically withdrawing, becoming hostile or aggressive, dissociating, and engaging in other anomalous maternal behaviors predictive of insecure and particularly disorganized attachment relationships (Schechter et al., Reference Schechter, Coates, Kaminer, Coots, Zeanah and Davies2008, Reference Schechter, Willheim, Hinojosa, Scholfield-Kleinman, Turner and McCaw2010). To date, no study has examined the roles of trauma characteristics, such as type and timing, on mother–infant attachment. Future research should consider a broad, lifetime perspective of trauma and examine how specific characteristics of maternal trauma histories may interact with PTSD to influence caregiving behaviors and the mother–infant attachment relationship to understand more fully intergenerational effects.

The findings of Study 2 suggest a role for an insecure mother–infant attachment history in the etiology of PTSD. Elucidating pretrauma vulnerability factors for PTSD has been highly challenging given the need to conduct prospective studies that enroll a large number of participants prior to trauma exposure and then follow them over a long period of time to ensure that a sufficient number of participants are trauma-exposed and develop PTSD to provide adequate power for analyses. Consequently, the large majority of PTSD studies begin after trauma exposure, anywhere from immediately postexposure (e.g., during hospitalization for an acute injury) to many years postexposure (e.g., adult survivors of childhood maltreatment). Thus, studies examining pretrauma characteristics that may influence PTSD risk have largely relied on retrospective report, which can suffer from recall bias. Moreover, any differences found between trauma-exposed individuals who did and did not develop PTSD in such studies may have been due to the effects of the trauma exposure and not to preexisting person characteristics.

The dose–response relationship between insecure attachment history and PTSD risk found in Study 2 suggests that the longer the mother–infant relationship is impaired, the greater the vulnerability to developing PTSD. Conversely, a child's vulnerability to PTSD may decrease if the mother–infant relationship improves. Prior research with this cohort documented that changes in attachment classification between 12 and 18 months were predicted by maternal and environmental characteristics (Sroufe et al., Reference Sroufe, Egeland, Carlson and Collins2005; Vaughn, Waters, Egeland, & Sroufe, Reference Vaughn, Waters, Egeland and Sroufe1979). Mothers in dyads who changed from secure to insecure were found to show little joy, pleasure, or gratification in their interactions with their infants at 6 months (Egeland & Farber, Reference Egeland and Farber1984; Sroufe et al., Reference Sroufe, Egeland, Carlson and Collins2005). Changing from insecure to secure was associated with decreases in stressful life events. Therefore, children's and adolescents' resilience to PTSD may be enhanced by identifying mother–infant dyads marked by low maternal enjoyment or insecure attachment behaviors and offering interventions that decrease maternal life stress and support positive mother–infant interactions. Such interventions may be particularly beneficial among groups at high risk of trauma exposure.