Borderline Kişilik Bozukluğu ve Travma Sonrası Stres Bozukluğu Arasındaki Köprü Belirtilerin Belirlenmesi: Ulusal Bir Kohorttan Bir Ağ Analizi - Identifying Bridge Symptoms Between Borderline Personality Disorder and Posttraumatic Stress Disorder: A Network Analysis From a National Cohort

Borderline Kişilik Bozukluğu ve Travma Sonrası Stres Bozukluğu Arasındaki Köprü Belirtilerin Belirlenmesi: Ulusal Bir Kohorttan Bir Ağ Analizi - Identifying Bridge Symptoms Between Borderline Personality Disorder and Posttraumatic Stress Disorder: A Network Analysis From a National Cohort

 

Authors: Mahdi Fayad, MD; Valentin Scheer, MD, MPH; Carlos Blanco, MD, PhD; Patrice Louville, MD; Marina Sánchez-Rico, PhD; Katayoun Rezaei, MPH; Nicolas Hoertel, MD, MPH, PhD; and Frédéric Limosin, MD, PhD

 

Translated by: Specialist Psychologist Gizem Pozam

 

 

Abstract

Objective: Borderline personality disorder (BPD) and posttraumatic stress disorder (PTSD) share common risk factors, including exposure to traumatic events. We aim to estimate networks of DSM-IV BPD and PTSD to describe interactions between the symptoms of these 2 disorders and identify bridge symptoms between the 2 diagnoses that may play a critical role in their co-occurrence.

Methods: We conducted a network analysis of data from the second wave of the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC 2004–2005), a nationally representative sample of the US adult population. Using a bootstrap method, we calculated network stability and centrality measures for each symptom across 3 different network estimates.

Results: The networks were highly stable. The symptom “Chronic feelings of emptiness” was the most central symptom in the BPD network. “Feelings of intense fear or horror” and “Recurrent and intrusive recollections of the traumatic event” were the most central symptoms in the PTSD network. The symptoms “Self-directed aggression,” “Severe dissociation,” “Chronic feelings of emptiness,” and “Feelings of detachment” had significantly higher bridge expected influence than most other symptoms in the network, both in the full sample and in the subsample of participants who responded to all PTSD and BPD symptom questions.

Conclusion: Self-directed aggression, chronic feelings of emptiness, dissociative symptoms, and feelings of detachment represent bridge symptoms between BPD and PTSD. These symptoms may potentially trigger and perpetuate symptoms of one disorder in the presence of the other. Targeting these symptoms may enable better prevention and management of both disorders.

J Clin Psychiatry 2024;85(4):23m15079

Author affiliations are listed at the end of this article .

 

 

Borderline personality disorder (BPD) is characterized by pervasive and persistent instability in emotion regulation, interpersonal relationships, self-image, and impulse control. Exposure to traumatic events is highly prevalent among individuals with BPD, with most reporting histories of neglect, abuse, harassment, and rejection by peers.1-4 Individuals with BPD also frequently present with comorbid disorders, such as mood, anxiety, substance use, and eating disorders.5-8 Among these comorbid disorders, posttraumatic stress disorder (PTSD) is particularly common. Approximately 29–55% of individuals with BPD have comorbid PTSD,9,10 and 24% of patients with PTSD have comorbid BPD.11 Although BPD and PTSD are currently regarded as distinct nosological entities, there is substantial overlap between the symptoms constituting their respective diagnostic frameworks.12 Recent literature has shown growing interest in complex PTSD (cPTSD), primarily because of the difficulties in distinguishing it from BPD and its symptom convergence with PTSD. Although they are considered distinct constructs, delineating the boundaries between these diagnoses and their co-occurrence can present a clinical challenge. 12-14

Network theory is a promising tool for exploring the complexity of mental health diagnoses.15 Network analysis aims to examine relationships between the symptoms of a disorder and rank them according to their importance within the network. This symptom hierarchy can be assessed using various metrics.15,16 Network analysis can also be applied jointly to multiple diagnoses to describe the relationships between symptoms of multiple disorders.17 This approach may help investigate comorbid diagnoses by enabling the identification of bridge symptoms, defined as symptoms that connect 2 or more disorders. These bridge symptoms are thought to play a critical role in the co-occurrence of disorders.17

In this report, network analysis was applied to outline the interactions between the DSM-IV symptoms of BPD and PTSD and to identify bridge symptoms between the 2 disorders. This information is important because bridge symptoms may represent therapeutic targets in clinical practice, enabling prevention and better management of co-occurring disorders.17 Using the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), a large, nationally representative sample, we aimed to obtain stable estimates that could be generalized beyond clinical samples.

 

MATERIALS AND METHODS

Sample

Data were obtained from the second wave (2004–2005) of NESARC, a nationally representative, face-to-face, prospective survey of the US adult population conducted by the National Institute on Alcohol Abuse and Alcoholism.18 The study included noninstitutionalized US residents aged at least 18 years. The overall response rate for the second wave was 70.2%, corresponding to 34,653 interviews.18

The NESARC research protocol, including written informed consent procedures, was fully approved by the US Census Bureau and the Office of Management and Budget. A total of 34,653 participants were analyzed, regardless of whether they met the diagnostic criteria for BPD or PTSD. Since the study aimed to identify bridges between the symptoms of the 2 diagnoses, we did not restrict the study to full-threshold disorders, in order to capture potential subsyndromal interactions19 and avoid Berkson’s bias.5,20-22 In accordance with network analysis theory, we considered that focusing solely on individuals meeting diagnostic criteria would be counterproductive.23

DSM-IV Assessment of Disorder Symptoms and Diagnoses

Diagnoses were assessed using the DSM-IV version of the Alcohol Use Disorder and Associated Disabilities Interview Schedule (AUDADIS-IV), a structured diagnostic instrument administered by lay interviewers.18

The test-retest reliability of the AUDADIS-IV BPD diagnosis is considered good (κ = 0.71, SE = 0.06), and the intraclass test-retest reliability coefficient is in the good range (95% intraclass correlation coefficient = [0.74–0.79], α = 0.83).24

Similarly, the test-retest reliability of the AUDADIS-IV PTSD diagnosis is considered robust (κ = 0.64, SE = 0.11), and the intraclass test-retest reliability coefficient is in the good range (95% ICC = [0.64–0.72], α = 0.84).24

Statistical Analysis

First, we estimated the network of each diagnosis independently and calculated centrality measures for each independent network. We then estimated a joint network for BPD and PTSD symptoms and calculated centrality measures to identify bridge symptoms. This step was performed because it established a reference point that allowed us to distinguish the importance of symptoms within their own networks from their bridging roles in the joint network.

Network estimation. For all network estimates, we applied the Ising model25 described by van Loo and colleagues,26 which is suitable for binary data. Each node in a network represents a DSM-IV symptom. The nodes, their corresponding abbreviations, and their prevalence among participants are provided in Supplementary Table 1. The hyperparameter γ, which controls how strongly the Extended Bayesian Information Criterion favors simpler models, was set to 0.25. The parameter γ is generally set between 0 and 0.5; higher values yield simpler models and thus fewer edges.27,28 This method is considered to have good specificity and acceptable sensitivity.25 Symptoms in the networks were assigned colors according to the DSM-IV diagnostic criterion to which they belonged.

Edge weights. Edges between nodes were estimated using regularized logistic regressions in which each node was regressed on the others. Edge weights correspond to the average of the coefficients obtained from the regularized logistic regression of node A on node B and node B on node A. Edge weights can be compared visually by examining edge thickness, with a thicker edge indicating a higher weight. Green edges represent positive correlations between nodes, whereas red edges represent negative correlations.

Centrality indices. Bridge strength indicates a node’s total connectivity with another disorder and represents the sum of the absolute values of the edge weights between that node and all nodes in another disorder.17 Bridge expected influence, on the other hand, indicates a node’s total connectivity with another disorder but does not treat edge weights as absolute values. Therefore, when negative edge weights are present in a network, bridge expected influence is the preferred metric, particularly when clinicians aim to target specific symptoms for therapeutic deactivation.29 Given the presence of several negative edges in the BPD/PTSD network, we chose to use bridge expected influence rather than bridge strength, as this metric may better reflect the nature of the interconnectedness of the diagnoses and help elucidate connections between diagnostic categories.

Network stability. The stability of each network was calculated using nonparametric and case-dropping bootstrap methods.16,27 Stability coefficients ranging from 0.25 to 0.5 are considered acceptable, whereas coefficients ranging from 0.5 to 0.75 are considered ideal and yield highly stable networks.16 Following previous recommendations,16 we calculated 1,000 bootstraps.

Handling missing data. Two distinct types of missing data were present in the dataset. First, missing cases were observed when participants chose not to answer certain questions. These missing values were considered missing at random, and the participants were excluded from the main analysis to prevent imputation biases (n = 1,366).

Second, missing data resulting from skip logic arose as a structural aspect of the survey design, in which certain questions were intentionally skipped based on participants’ previous responses. This occurred because participants who did not meet DSM-IV criterion A for PTSD were not asked about other PTSD symptoms. Missing values for these variables were therefore imputed as “0” or “No,” as implied by the survey’s skip logic. To address potential biases introduced by the imputation method used,27 we conducted a sensitivity analysis including only participants who answered all questions (i.e., the subpopulation who met DSM-IV criterion A for PTSD).

For data preprocessing, thePandas30(v2.1.4) and Numpy31( v1.26.3) Python32(v3.12.1) libraries were used. Network estimates, bootstraps, and visualizations were computed using R software version 3.6.3 (R Project for Statistical Computing, R Core Team, Vienna, Austria) and the IsingFit33 (v0.4), qgraph34 ( v1. 9.8) and bootnet16 ( v1 . 5 .6) R libraries.

Results

A description of the sample population is available in Table 1. The participant selection process for the main and sensitivity analyses is summarized in Supplementary Figure 1. The stability coefficients obtained after 1,000 bootstraps for expected influence and bridge expected influence in all estimated networks were ideal (correlation-stability coefficient = 0.75), yielding reliable network estimates (Supplementary Figures 2–4).

 

 

BPD Network

The estimated BPD network is presented in Figure 1. Lasso-penalized odds ratios (ORs) for nonparametrically bootstrapped edge weights between pairs of nodes are presented in Supplementary Table 2, and edge weight intervals are presented in Supplementary Figure 5. The highest edge weights in this network were between “Mood reactivity” and “Chronic feelings of emptiness” (OR = 5.19, 95% CI = [4.57; 5.90]) and between “Chronic feelings of emptiness” and “Self-directed aggression” (OR = 3.30, 95% CI = [2.81; 3.89]). “Self-directed aggression” was primarily associated with symptoms of emotional dysregulation (“Chronic feelings of emptiness,” “Marked mood reactivity,” and “Anger”).

The expected influence of BPD symptoms is shown in Supplementary Figure 6. The symptom “Chronic feelings of emptiness” had the highest score, indicating its high importance within the network. “Mood reactivity” and “Anger” were also central symptoms in terms of expected influence. The expected influence of these 3 BPD symptoms was found to be significantly greater than that of all other BPD symptoms (Supplementary Figure 7).

 

PTSD Network

The estimated PTSD network is presented in Figure 2. ORs and edge weight intervals are presented in Supplementary Table 3 and Supplementary Figure 8, respectively. The highest edge weights in the network were between “Feelings of detachment or estrangement” and “Restricted range of affect” (OR = 9.31, 95% CI = [8.01; 10. 08]), between “Intense fear or horror during the event” and “Recurrent and intrusive distressing recollections of the event” (OR = 8.07, 95% CI = [7.53; 8.74]), and between “Hypervigilance” and “Exaggerated startle response” (OR = 7.27, 95% CI = [6.50; 8.09]).

The expected influence of PTSD symptoms is shown in Supplementary Figure 9. The symptoms “Recurrent and intrusive distressing recollections of the event,” “Intense fear or horror during the event,” and “Efforts to avoid thoughts, feelings, or conversations associated with the event” scored significantly higher than all other symptoms, indicating high connectivity with other symptoms in the network (Supplementary Figure 10).

BPD/PTSD Network

The estimated BPD/PTSD network is presented in Figure 3. Cross-diagnostic ORs and edge weight intervals are shown in Supplementary Table 4 and Supplementary Figure 11, respectively.

The highest edge weights in the network were between the symptoms “Self-harm and suicidal gestures” (BPD) and “Feelings of detachment or estrangement” (PTSD) (OR = 1.50, 95% CI = [1.26; 1. 94]), “Inappropriate anger” (BPD) and “Irritability and anger” (PTSD) (OR = 1.50, 95% CI = [1.37; 1.94]), and “Chronic feelings of emptiness” (BPD) and “Restricted range of affect” (PTSD) (OR = 1.46, 95% CI = [1.23; 1.73]). Bridge expected influence for BPD and PTSD symptoms is shown in Figure 4. “Self-harm and suicidal gestures,” “Transient paranoid ideation or severe dissociative symptoms,” and “Chronic feelings of emptiness,” together with the PTSD symptom “Feelings of detachment or estrangement,” scored highest in terms of bridge expected influence. Bridge expected influence for these 3 BPD symptoms was significantly higher than that of 21 of the other 25 symptoms in the network, whereas “Feelings of detachment or estrangement” scored significantly higher than 13 of the other 17 PTSD symptoms (Supplementary Figure 12). These results were maintained in the sensitivity analysis that included only the subpopulation of participants who answered all PTSD questions (Supplementary Figure 13).

Symptoms belonging to the PTSD “Intrusion” criterion had lower bridge expected influence on average than other PTSD symptoms.

 

 

 

 

 

 

DISCUSSION

In a large, nationally representative sample, we examined network structures and bridge symptoms between BPD and PTSD. In the BPD network, “Chronic feelings of emptiness” showed the highest overall connectivity, highlighting its role in activating other BPD symptoms. This symptom also showed a strong correlation with “Self-harm and suicidal gestures.”

This symptom has been associated with an increased risk of suicide attempts,4 and it has been suggested that focusing on feelings of emptiness reduces suicide risk among patients with BPD.35,36 The strong correlation between “Chronic feelings of emptiness” and “Marked mood reactivity” in the estimated network reinforces the importance of specifically managing this symptom. “Marked mood reactivity” accounts for some of the functional impairment among patients with BPD, particularly social impairment,37 which in turn increases suicide risk.38 Specific management of chronic feelings of emptiness and mood reactivity may be effective in reducing the risk of self-harm and suicidal behavior among patients with BPD.

 

 

The estimated PTSD network indicates that the symptoms “Recurrent and intrusive distressing recollections of the event,” “Intense fear or horror during the event,” and “Efforts to avoid thoughts, feelings, and conversations associated with the event” are central to the network.

Previous studies have also indicated the centrality of avoiding thoughts and feelings39 and recalling the event.40 Our results are further supported by several studies focusing on intrusive recollections of traumatic events41 and the specific management of these recollections through thought-control techniques.42 For example, formal practice of mindfulness meditation reduced PTSD severity scores and associated depressive cognitions.43 Our results are also comparable to those described in a recent meta-analysis of PTSD networks.44 According to that analysis, intrusion and internal avoidance symptoms have high expected influence, whereas “Amnesia” and “Sense of a foreshortened future” have low expected influence.

In the BPD/PTSD network, the strongest interaction between symptoms of the two disorders was between “Feelings of detachment or estrangement” and “Self-harm and suicidal gestures.”

Previous studies indicate that, among PTSD symptoms, feelings of detachment show the strongest correlation with suicidal ideation.45 Specifically targeting this symptom may be useful for reducing suicide risk in clinical practice. “Feelings of detachment or estrangement” are also associated with a higher risk of impaired social interactions among patients with PTSD.46 Its role as a bridge symptom between PTSD and BPD is therefore supported, as impaired social interactions are among the criteria for BPD.47 Personality disorders are frequently diagnosed among patients with PTSD, and scores for feelings of detachment or estrangement have the highest predictive value for accurately distinguishing individuals with and without a personality disorder.48 This observation is consistent with our findings, as we identified this symptom as the PTSD symptom with the highest bridge centrality. Management of this symptom would therefore be of interest for several reasons. First, its presence may encourage practitioners to investigate comorbid personality disorders (particularly BPD) in patients seeking health care for trauma-related symptoms. Conversely, underlying trauma should be explored when patients with BPD express feelings of detachment or estrangement. It is also important to emphasize that feelings of detachment and, more generally, symptoms related to emotional dysregulation have been removed from the PTSD criteria in the International Classification of Diseases, Eleventh Revision (ICD-11), and included in the cPTSD criteria.49 Our findings support this change, as we identified feelings of detachment as a bridge symptom between BPD and PTSD in this study, and cPTSD describes persistent difficulties in feeling close to others and sustaining relationships. Furthermore, although self-directed aggression is not explicitly included in the ICD-11 criteria for cPTSD, it has previously been suggested to be a potentially central symptom in cPTSD50 and in recent models of cPTSD in children and adolescents.51 These models, which include symptoms associated with externalizing / impulsive disorders, suggest a potential link with self-directed aggression, as seen in the concept of developmental trauma disorder.52

 

 

Notably, the BPD symptoms that constituted bridge symptoms in our study are comparable to the results of the latent class analysis by Cloitre and colleagues.53 In their study, feelings of emptiness, dissociation, and self-directed aggression did not distinguish BPD from cPTSD, whereas the presence of “Identity disturbance,” “Efforts to avoid abandonment,” “Relationship instability,” and “Impulsivity” increased the likelihood of belonging to the BPD group rather than the cPTSD group.

“Chronic feelings of emptiness” was identified as the most central symptom in the BPD network while also constituting a bridge symptom between BPD and PTSD, reinforcing its importance both within and across diagnoses. However, although dissociation was identified as a key bridge symptom, it exhibited only moderate expected influence within the BPD network. This finding is consistent with previous publications describing correlations between traumatic experiences and the severity of dissociation.54-56 Conversely, the central symptoms identified in the PTSD network played marginal roles in bridging BPD and PTSD, as intrusion symptoms exhibited lower bridge expected influence than affect-related symptoms.

Finally, the bridge between BPD and PTSD symptoms may be explained by the consequences of the traumatic event, particularly emotional symptoms, rather than the event itself. The strong connection between chronic feelings of emptiness in BPD and restricted range of affect in PTSD reflects this observation. The cross-diagnostic importance of these emotional symptoms is also supported by neuroimaging and neurocognitive evidence, such as hyperactivation of the limbic system57 and greater allocation of cognitive resources to emotional information in patients with BPD or PTSD compared with healthy individuals.58

This study has several limitations. First, the binary nature of the data likely reduced the precision of the findings. Second, the data are cross-sectional, which does not allow causal interpretation of the edges in the network.16 Third, our results may not be generalizable to other countries or to clinical subgroups of patients with BPD or PTSD.59,60 Future longitudinal studies are needed to replicate our results and expand their potential clinical applications, particularly with regard to their generalizability to clinical samples; in this study, it was possible to distinguish specifically between simple and complex PTSD, as the diagnostic construct is absent from DSM-IV. cPTSD is particularly important given that one of its core symptoms of emotion dysregulation, namely emotional numbing, can be considered comparable to the core BPD symptom of emotional emptiness. The bridge symptoms identified in this study appear to be associated with the relational detachment symptoms of cPTSD, suggesting that cPTSD should be investigated as a potential bridge between BPD and PTSD. Furthermore, the cognition and mood symptoms added to the DSM-V PTSD diagnostic criteria are also absent from our study. Fifth, although the bridge symptoms identified in the study held up in the sensitivity analysis,27 imputation for questionnaires with skip patterns is strongly recommended when conducting network analysis.

In this study, we highlighted the importance and centrality of chronic feelings of emptiness among BPD symptoms, both within the BPD network and as a bridge symptom to PTSD. Intrusive recollections of traumatic events and, more broadly, symptoms of the “Intrusion” criterion were among the most central symptoms of PTSD but played marginal roles in bridging BPD and PTSD. Feelings of detachment or estrangement were strongly linked to self-harm and suicidal gestures, highlighting the importance of specifically managing these bridge symptoms in patients with co-occurring BPD and PTSD. Dissociative symptoms also played a role in bridging the 2 disorders. Targeting these specific symptoms may be effective in reducing the burden and suffering associated with these disorders.