Post-Traumatic Cognitions Inventory (PTCI): psychometric properties in clients with serious mental illness and co-occurring PTSD

Abstract Background: People with post-traumatic stress disorder (PTSD) exhibit negative cognitions, predictive of PTSD severity. The Post-Traumatic Cognitions Inventory (PTCI) is a widely used instrument measuring trauma-related cognitions and beliefs with three subscales: negative thoughts of self (SELF), negative cognitions about the world (WORLD), and self-blame (BLAME). Aims: The current study attempted to validate the use of the PTCI in people with serious mental illness (SMI), who have greater exposure to trauma and elevated rates of PTSD, using confirmatory factor analysis (CFA) and examining convergent and divergent correlations with relevant constructs. Method: Participants were 432 individuals with SMI and co-occurring PTSD diagnosis based on the Clinician Administered PTSD Scale, who completed PTCI and other clinical ratings. Results: CFAs provided adequate support for Foa’s three-factor model (SELF, WORLD, BLAME), and adequate support for Sexton’s four-factor model that also included a COPE subscale. Both models achieved measurement invariance at configural, metric and scalar levels for three diagnostic groups: schizophrenia, bipolar and major depression, as well as for ethnicity (White vs Black), and gender (male vs female). Validity of both models was supported by significant correlations between PTCI subscales, and self-reported and clinician assessed PTSD symptoms and associated symptoms. Conclusions: Findings provide support for the psychometric properties of the PTCI and the conceptualization of Sexton’s four-factor and Foa’s three-factor models of PTCI among individuals diagnosed with SMI (Foa et al., 1999).


Introduction
It is well established that people with post-traumatic stress disorder (PTSD) have negative cognitions, i.e. a negative perception of self and negative world view (e.g. Ehlers and Clark, 2000;Foa and Cahill, 2001;Foa and Rothbaum, 1998), which have recently been incorporated into the DSM-5 criteria for PTSD (American Psychiatric Association, 2013). Research has shown clinically meaningful connections between negative post-traumatic cognitions and PTSD symptoms (e.g. Beck et al., 2004;Foa et al., 1999;Shin et al., 2020), and demonstrated that such beliefs are predictive of PTSD severity (Brown et al., 2018). According to cognitive models of PTSD, negative beliefs about the self and others can maintain perceptions of continuing threat and prevent effective coping (Ehlers and Clark, 2000;Foa and Rothbaum, 1998). Furthermore, when individuals with PTSD experience distress, they may feel vulnerable, which can promote the development of negative beliefs, which may in turn maintain other PTSD symptoms (Shahar et al., 2013).
Individuals diagnosed with serious mental illness (SMI), typically defined as any major psychiatric disorder, such as schizophrenia, schizoaffective disorder, major depression and bipolar disorder, accompanied by persistent functional impairments (Martínez-Martínez et al., 2020;Substance Abuse and Mental Health Services Administration, 2017), who have experienced childhood trauma, have poorer clinical outcomes than those not exposed, including higher levels of repetitive negative thinking, dysfunctional metacognitive beliefs, and more severe symptoms (Grubaugh et al., 2011;Mansueto et al., 2021;Struck et al., 2020). Although SMI has typically been linked to schizophrenia, bipolar disorder and treatment refractory major depression (Bigdeli et al., 2022;Grubaugh et al., 2021;Parabiaghi et al., 2006), consensus is lacking in terms of the specific disorders included (Martínez-Martínez et al., 2020). SMI categorizations in many jurisdictions in the United States include DSM diagnoses, other than the typical SMI-related conditions above, when there is accompanying persistent impairment in functioning. SMI in this study is broadly defined as a major psychiatric disorder such as schizophrenia, bipolar and major depressive disorder, with resultant serious functional impairment. Individuals with SMI are at greater risk for trauma exposure (Grubaugh et al., 2011;Grubaugh et al., 2021;Struck et al., 2020) than people in the general population, with multiple traumatizations common Mueser et al., 2004). The high exposure to trauma in persons with SMI is associated with high rates of co-occurring PTSD, typically ranging between 25 and 48% of current PTSD (Grubaugh et al., 2011), considerably higher than the estimated 3.5% current prevalence in the general population (Kessler et al., 2005). PTSD contributes to a worse course of SMI, and more severe symptoms, including anxiety, depression and psychosis (Mueser et al., 2004;Seow et al., 2016). PTSD can be effectively treated in people with SMI and there is evidence that changes in PTSD symptoms are mediated by changes in trauma-related cognitions in people with SMI (Mueser et al., , 2015, as reported in the general population (e.g. Brown et al., 2018;Germain et al., 2016). Scales for measuring negative trauma-related cognitions in SMI populations are therefore important.
The Post-Traumatic Cognitions Inventory (PTCI; Foa et al., 1999) is a commonly used measure of trauma-related cognitions and beliefs. The PTCI contains 36 statements, with three subscales assessing negative cognitions about the self (SELF subscale; 21 items), the world (WORLD subscale; 7 items), and self-blame (BLAME subscale; 5 items). The initial three-factor model was based on the 33 items of its initial validation study (Foa et al., 1999). Three items were added to the original scale for exploratory purposes, and inclusion of these items in further analyses in other studies led to a four-factor solution in some of those studies (Sexton et al., 2018). The PTCI also discriminated between traumatized individuals with and without PTSD and was found to be sensitive to treatment changes (Foa and Rauch, 2004;Germain et al., 2016).
validity, the BLAME subscale demonstrated poor convergent validity by failing to correlate with measures of PTSD, depression or quality of life, and poor discriminant validity by failing to discriminate between individuals with versus without PTSD. Similar findings were reported by Su and Chen (2008) and Daie-Gabai et al. (2011) in samples of participants with mixed trauma histories. One possible explanation for the discrepant findings on the factor structure of the PTCI across these studies may be differences in the traumatic events experienced by the participants. The samples of Foa et al. (1999) and van Emmerik et al. (2006) included victims of interpersonal violence, the sample of Beck et al. (2004) consisted solely of survivors of MVAs, while Su and Chen (2008) and Daie-Gabai et al. (2011) included individuals with mixed trauma histories. While most studies of the PTCI have focused on the three-factor model, a recent study among veterans found support for a four-factor model (Sexton et al., 2018). In this study, exploratory and confirmatory factor analyses of PTCI supported the presence of a stable fourth factor (labelled COPE, consisting of three items that originally loaded onto the SELF subscale) that can be described as perceived lack of competence at handling strong negative emotional states.
Although the psychometric properties of the PTCI have been examined in a range of traumaexposed groups, they have not yet been investigated among individuals with SMI (Table 1). Prior studies suggest that clients with SMI and co-occurring PTSD score significantly higher on the PTCI (Mueser et al., , 2015 than sexual assault survivors (Andreu et al., 2017), MVA victims (Beck et al., 2004), and veterans (Sexton et al., 2018). Given that trauma is highly prevalent and disabling among people with SMI, there is a need to investigate the factor structure and construct validity of PTCI in this population. The aims of the study therefore were to explore the factor structure and psychometric properties of the PTCI among individuals with SMI. We hypothesized that the Sexton et al. (2018) four-factor model would have the best fit, while the three-factor model would demonstrate adequate fit based on existing studies on the factor structure of the PTCI (Table 1). Prior studies have found mixed support for the three-factor model, whereas the study of Sexton et al. (2018) in a large treatment-seeking veteran sample supported the four-factor model over the three-factor model. We further hypothesized that the PTCI subscales would show good internal consistency across three different samples of people with SMI, and that PTCI subscales would be moderately and significantly correlated with PTSD symptom severity and other psychiatric symptoms (suggesting convergent validity), but not PTSD knowledge or working alliance, constructs unrelated to post-traumatic cognitions (suggesting divergent validity).

Participants
Participants for analyses came from three studies (see Table 2). The first sample was drawn from a randomized controlled trial (RCT) and conducted in New Hampshire/Vermont, USA at four community mental health centers (Study 1; n = 108; Mueser et al., 2008). Participants met the following criteria: (1) >18 years old; (2) determination by New Hampshire or Vermont as having a SMI, defined as a DSM-IV Axis I disorder and persistent impairment in work, school, or ability to care for oneself; (3) diagnosis of major depression, bipolar disorder, schizoaffective disorder, or schizophrenia confirmed through Structured Clinical Interview of DSM-IV disorders (SCID; First et al., 1996); and (4) current diagnosis of PTSD based on Clinician Administered PTSD Scale (CAPS; Blake et al., 1990).
The second sample was drawn from participants in a RCT conducted in partial hospitalization programs and out-patient programs within a community mental health service system in New Jersey, USA (Study 2; n = 199; Mueser et al., 2015). Inclusion criteria were: (1) >18 years old; (2) met State of New Jersey definition of SMI; (3) diagnosis of schizophrenia, schizoaffective disorder, major depression, or bipolar disorder, based on the SCID (First et al., 1996); and (4) diagnosis of severe PTSD, based on the CAPS, schizophrenia version (Gearon et al., 2004), with a minimum total score of 65. Exclusion criteria included having a hospitalization, suicide attempt, or substance dependence within the past three months.
The third sample was drawn from a RCT for treatment of PTSD among 132 participants recruited from 12 vocational rehabilitation programs at community mental health centres in three Northeastern states in the USA (Study 3; n = 125; Lu et al., 2022). Inclusion criteria for Study 3 were: (1) >18 years old; (2) received supported employment services within the past 24 months; (3) in treatment for SMI, with diagnosis based on self-report; (4) current diagnosis of PTSD, determined by the CAPS-5 (Weathers et al., 2018); (5) no current chart diagnosis of alcohol or drug dependence; and (6) no hospitalizations or suicide attempts in the past two months.
Across all three studies, participants had SMI diagnosis and confirmed co-occurring PTSD diagnosis using CAPS or CAPS-5. The majority of participants were female (69%) and in their late 40s (Table 2). Participants predominantly (98%) had diagnosis of schizophrenia,  schizoaffective disorder, bipolar disorder, or major depressive disorder. For primary SMI diagnosis, all studies had more representation of non-psychotic (i.e. mood disorders) than psychotic disorders (16% for Study 1, 34% for Study 2, and 36% for Study 3). The racial composition differed significantly between studies, with the majority of participants in Study 1 being White, the majority being non-White in Study 2, and an approximately equal proportion of White and non-White participants in Study 3. Across all studies, 51% of participants were White and 38% were Black.

Measures
Participants in all three studies completed baseline assessments prior to randomization. Only baseline data were used for the present analyses.
Posttraumatic Cognitions Inventory (PTCI; Foa et al., 1999) The PTCI was used to assess trauma-related cognitions. The PTCI is a self-report measure pertaining to common negative thoughts and beliefs about self, other people, and the world in individuals with PTSD (Foa et al., 1999). The PTCI consists of 36 items ranging from 1 (totally disagree) to 7 (totally agree). It has good test-retest reliability and has been shown to be particularly effective at discriminating between traumatized individuals with PTSD and those without (Foa et al., 1999). In detecting PTSD, sensitivity ranged from .70 to .78 and specificity ranged from .81 to .93 (Beck et al., 2004;Foa et al., 1999). Both subscale scores and total scores are based on the original 33 items (Foa et al., 1999). In the current investigation, Cronbach's alpha for the 36-item PTCI total score was .95, .94, .96 and .95 in Studies 1-3, and total combined sample, respectively.
Beck Depression Inventory (BDI-II; Beck, 1996) The BDI-II is a 21-item self-report questionnaire used in all three studies to measure depression. Average internal consistency coefficient was .86 with excellent validity . The internal consistency of the BDI-II was .93, .91 and .91 for Studies 1-3, respectively.
Beck Anxiety Inventory (BAI; Beck and Steer, 1993) The BAI is a 21-item scale measuring self-reported anxiety in all three studies. The BAI discriminates between anxiety and depression and has high test-retest reliability . The questionnaire describes emotional, physiological and cognitive symptoms of anxiety. The internal consistency of the BAI was .93, .94 and .91 for Studies 1-3, respectively.
Expanded version of the Brief Psychiatric Rating Scale (BPRS; Lukoff et al., 1986) The expanded version of the BPRS was used in Studies 1 and 3 to assess psychiatric symptoms. This interview-based measure includes 24 items, rated on a 7-point Likert scale. The BPRS is a measure of the severity of psychiatric symptoms; it has excellent psychometric properties and has established factor structure in SMI population (Mueser et al., 1998).
Positive and Negative Syndrome Scale (PANSS; Kay et al., 1987) The PANSS is a 30-item interview-based measure used in Study 2 to measure psychiatric symptoms. Each item is rated on a 7-point Likert scale (from 'absent' to 'extreme'). The scale consists of three subscales: positive, negative, and general psychopathology. Internal consistency ranged from .85 to .88 (Citrome et al., 2011;Lancon et al., 2000) and test-retest reliability ranged from .77 to .89 (Kay et al., 1987).
Structured Clinical Interview for DSM-IV Axis-II Personality Disorders (SCID II; First et al., 1995) The SCID II Borderline Personality Module was used in Studies 1 and 2 to assess interpersonal functioning with items including unstable relationships, recurrent self-injurious/suicidal behaviour, mood instability and more.
Quality of Life Interview (QOLI; Lehman et al., 1995) The QOLI is a 74-item instrument used in Study 2 to assess quality of life on a 7-point scale.
Internal consistency ranged from 0.68 to 0.85 (Lançon et al., 1999). Test-retest reliability ranged from .28 to .98, and validity is good based on confirmatory factor analyses and multivariate predictive models (Lehman, 1996).
PTSD Knowledge Scale (K-PTSD; Pratt et al., 2005) The K-PTSD was used in Studies 1 and 2 and assessed understanding of PTSD. It contains 15 multiple choice questions in relation to PTSD. Previously it has demonstrated sensitivity to changes following psychoeducational interventions about trauma for people with psychiatric disabilities (Pratt et al., 2005). The internal consistency of the K-PTSD was .65 for Study 1 and .48 for Study 2.
Patient version of the Working Alliance Inventory (WAI; Horvath and Greenberg, 1989) The patient version of the WAI was used in Studies 1 and 2 to rate the therapeutic alliance with case managers (i.e. not the therapist providing CBT treatment). Internal consistency estimates for the patient version ranged from .83 to .97 (Hanson et al., 2002). The measures utilized in each study are presented in the Supplementary material.

Data analysis
Confirmatory factor analyses (CFA) with maximum likelihood estimation with robust standard errors (i.e. MLR estimator) using Mplus 8.7 was conducted to identify the best fitting model. There were 15,552 data points on PTCI for the total sample (N = 432), of which 306 (1.95%) were missing data. Missing data were included in the analysis by using Full Information Maximum Likelihood (FIML) in Mplus software. Missing data were handled using pairwise deletion in correlational analysis. Model goodness of fit was evaluated using indices: model χ 2 test, comparative fit index (CFI), Tucker-Lewis index (TLI), standardized root mean square residual (SRMR), and root mean square error of approximation (RMSEA). Models with reasonably good fit may have CFI and TLI values that exceed 0.90 (Kline, 2005). Using two-index presentation strategy, a cut-off value close to .95 for CFI and TLI, a cut-off value close to .08 for SRMR, and a cut-off value close to .06 for RMSEA are needed to establish relatively good fit (Hu and Bentler, 1999).
Multi-group CFA was conducted to examine measurement invariance of models across the three primary diagnostic samples of SMI (schizophrenia-schizoaffective disorder, major depression, and bipolar disorder). Configural, metric and scalar invariance were used to determine the degree of invariance of PTSD between groups, as suggested by Gregorich (2006) and Meredith (1993). Configural invariance determined if there was adequate fit and if the relationships between variables could be considered equivalent. Metric invariance tested if both groups contributed similar regression weights to the latent construct. Scalar invariance determined if both groups had equivalent intercept values in the latent construct on the observed variable of item scores (Gregorich, 2006;Meredith, 1993). More stringent criteria were applied when the total N>300, including a change <.01 in CFI supplemented with a change of <.015 in RMSEA and <.03 in SRMR for metric invariance; and a change of <0.01 in CFI supplemented with a change of <.015 in RMSEA and <.01 in SRMR for scalar invariance (Chen, 2007). Convergent validity was calculated using correlations between PTCI scales and measures of trauma symptom severity, anxiety, depression, psychiatric symptoms, and quality of life. Divergent validity was evaluated by correlations between PTCI scales, knowledge of PTSD, and working alliance.

Results
Participants in the three studies met PTSD criteria using CAPS or CAPS-5, and had moderate to severe depression on average and moderate to severe anxiety. Participants in both Studies 1 and 2 had severe PTSD on average (CAPS >65). Total PTCI scores did not differ across the three samples (see Table 2).
Altogether, CFA analysis and multi-group CFA indicated that four-factor models had a similar fit to the three-factor model. To evaluate convergent validity, correlations were computed between the PTCI total score and its factor scores for Foa's three-factor model, Sexton's four-factor model, measures of clinician-rated (CAPS, CAPS-5) and self-reported PTSD symptoms (PCL-5), depression (BDI-II), and anxiety (BAI), (Table 4). PTCI total scale and subscales for each of the three models were significantly correlated with clinician-rated PTSD symptoms, and client's self-reported PTSD symptoms and depression severity. The PTCI subscale of SELF was more strongly correlated with BDI-II (r = .74; 95% CI: .69-.77; p < .01) than the other subscales in the models (r's ranged from .32 to .54; 95% CI ranged from .23-.40 to .47-.61; p < .01). For both models, the correlations were of comparable magnitude. The fourth PTCI subscale of COPE reported in Sexton's model, was significantly correlated with depression, PTSD symptoms, clinician-rated and self-reported PTSD symptoms, and anxiety (r ranged from .23 to .53). Its correlation patterns were similar to that of SELF subscale in Sexton's model, though at a lesser magnitude. Convergent validity studies thus support both models.
The internal consistency for the overall PTCI was .95 for the combined data sets from three studies (n = 432) [.95 for Study 1 (n = 108); .94 for Study 2 (n = 199); .95 for Study 3 (n = 125)]. The internal consistencies of the PTCI subscales for the three and four factor model were also high, ranging from .77 to .94 (Table 5).

Discussion
Our study used CFA as well as multi-group CFA to assess two different models proposed by previous literature. Sexton et al. (2018) found the superiority of the four-factor model over Foa's three-factor model. We did not find support for the hypotheses that Sexton's four-factor model would be superior to Foa's three-factor model, and instead found that the four-factor model performed similarly to the three-factor model, with both having adequate fit. Our study offers support for Sexton's four-factor model; however, support is also found for Foa's threefactor model. Both models have adequate fit in this sample, which contributes to their credibility for continued use, although future research is warranted.
The findings from this study strongly support the reliability and validity of the PTCI in people with SMI and co-morbid PTSD. Furthermore, we found adequate support for the three-factor structure of the PTCI initially reported by Foa et al. (1999), as well as for the four-factor model of Sexton et al. (2008).
Consistent with Sexton et al. (2018), the current study found that the four subscales in the fourfactor model of PTCI had good internal consistency. Moreover, the PTCI total scale and subscales also had moderate convergent correlations with measures of PTSD symptom severity, depression and anxiety. Evidence for divergent validity of PTCI was also found with weaker correlations with measures of PTSD knowledge and working alliance (r ranged from -.07 to -.16), a construct unrelated to post-traumatic cognition.
While the three-factor solution was found to show good fit, CFA analysis and multi-group CFA across the three diagnostic groups indicated that the four-factor solution had a better fit than the three-factor solution. Both models performed similarly across gender and race (White vs Black). Sexton's model has previously been used with veterans seeking treatment for military trauma but not among individuals with SMI until this study. Similarly, this study is the first time Foa's model was examined among individuals with SMI and co-occurring PTSD. With regard to PTCI subscales, results are consistent with Su and Chen (2008) in that all subscale scores had moderate to high correlations with depression as measured by the BDI. The SELF subscale was the strongest predictor of depression and a stronger predictor of PTSD severity than the other scales, in both the three-and four-factor solutions. In contrast to Su and Chen (2008), our study found that PTSD severity (CAPS and PCL) was most weakly correlated with the PTCI BLAME subscale. These findings are consistent with Daie-Gabai et al. (2011), who reported that the BLAME subscale had the lowest correlations with PTSD severity and depression symptoms compared with the SELF subscale, which was the strongest predictor of PTSD severity and depression, followed by the WORLD subscale.
Interestingly, the COPE subscale in Sexton's four-factor model was moderately correlated with PTSD symptoms, psychiatric symptoms, borderline personality functioning, and quality of life. Next to SELF subscale, COPE had the second strongest correlations with depression (BDI), anxiety (BAI), and PTSD symptoms (PCL) among all the subscales (r ranged from 0.22 to 0.54). The findings suggest the importance of addressing coping mechanisms in PTSD treatment due to its strong correlations with PTSD symptoms and overall psychiatric symptoms. The COPE subscale suggests that a perceived lack of competence in coping is also a strong predictor of borderline personality functioning, quality of life, and psychiatric symptoms among individuals with SMI and co-morbid PTSD. The findings are consistent with Mueser et al. (2008Mueser et al. ( , 2015's treatment in which cognitive restructuring was used to help people with SMI to increase their competence in coping with upsetting situations. This is consistent with PTSD treatment guidelines in which non-trauma-focused therapies (i.e. stress inoculation training, present-centered therapy, and interpersonal psychotherapy) also facilitate recovery from PTSD (Cusack et al., 2016;Watts et al., 2013).
Several important limitations should be noted. First, our study included clients with SMI and co-occurring PTSD who sought treatment. Therefore, these participants may have more severe psychiatric symptoms and higher scores on post-traumatic cognition than those without PTSD, or not currently in treatment. In Studies 1 and 2, participants' PTSD was assessed using DSM-IV criteria. Future research with the updated PTSD criteria in the DSM-5 (American Psychiatric Association, 2013) is needed to verify that findings are generalizable. Additionally, divergent validity was examined using correlations of PTSD knowledge and working alliance rather than measures of different symptoms or cognitions, which future studies may utilize instead.
These limitations notwithstanding, the current study is the first to examine the factor structure of the PTCI among three heterogeneous samples of people with SMI and co-occurring PTSD, and adds to the knowledge of the psychometric properties of this measure with special populations. Even though the three-factor model (SELF, WORLD, BLAME) appeared robust with SMI clients, the four-factor models (SELF, WORLD, BLAME, COPE) provided an alternative and better fit for this population. Overall, the PTCI appears to be a reliable and valid tool for assessing traumarelated beliefs in people with SMI and co-occurring PTSD.
Supplementary material. To view supplementary material for this article, please visit https://doi.org/10.1017/ S1352465823000140 Data availability statement. At the time that the grant was awarded, the funding agency did not require grantees to share data. We do not have participant consent or IRB approval to share data publicly.