Personality and trajectories of posttraumatic psychopathology: A latent change modelling approach
Introduction
Comorbidity between psychiatric disorders is the rule rather than the exception, with some patterns of comorbidity more common than others (Creamer, Burgess, & McFarlane, 2001; Chapman et al., 2012; Kessler, Sonnega, Bromet, Hughes, & Nelson, 1995). The tendency for disorders to cluster together in predictable patterns can be accounted for by the existence of two overarching latent factors, known as the internalizing and externalizing dimensions of psychopathology. Among the common psychiatric disorders, posttraumatic stress disorder (PTSD), depression, and anxiety load on the internalizing dimension, while substance use disorders load on externalizing (Eaton et al., 2013, Krueger, 1999; Krueger, Caspi, Moffitt, & Silva, 1998; Slade and Watson, 2006, Vollebergh et al., 2001).
Each of these dimensions, in turn, is closely associated with particular personality traits; internalizing with high levels of negative emotionality (and less consistently, with low levels of positive emotionality), and externalizing with low levels of constraint (or conversely, high levels of dishinibition) (Krueger, McGue, & Iacono, 2001; Kotov, Gamez, Schmidt, & Watson, 2010). Understanding the link between personality and these higher order internalizing and externalizing factors has been critical in making sense of the patterns of comorbidity and manifest psychopathology observed across clinical populations.
The internalizing/externalizing model has since been adapted by researchers interested in the expression of individual disorders; in particular, PTSD. In a model replicated in numerous studies (Castillo et al., 2014; Forbes, Elhai, Miller, & Creamer, 2010; Miller, Greif, & Smith, 2003; Miller and Resick, 2007, Miller et al., 2012; Rielage, Hoyt, & Renshaw, 2010), Miller et al. proposed that PTSD could be conceptualised as a microcosm of psychopathology; with an internalizing subtype associated with high NEM, low PEM, and high rates of comorbid internalizing disorders, and an externalizing subtype associated with high NEM, low CON, and high rates of externalizing disorders. The model also includes a third, ‘low pathology’ subtype, reflecting ‘normal’ personality and minimal comorbidity. In considering these subtypes, it is important to remember that they are subtypes of an internalizing disorder; thus, the externalizing subtype of PTSD is distinct from the externalizing dimension of psychopathology.
This is an important distinction as, while Miller’s model is helpful in understanding the expression of PTSD comorbidity, it is not clear whether it applies to trauma populations more broadly. PTSD patients represent only a small minority of the trauma-exposed population, with other internalizing and externalizing disorders also common in their own right rather than being secondary to PTSD (Bryant et al., 2010; Fetzner, McMillan, Sareen, & Asmundson, 2011). The extent to which personality typologies are predictive of these alternative responses to trauma is less well understood, although there is some evidence for the relationship between individual traits and internalizing/externalizing responses (Koffel et al., 2016). In addition, the majority of trauma survivors will not develop significant psychopathology at all (Bonanno et al., 2012; DeRoon-Cassini, Mancini, Rusch, & Bonanno, 2010), and the personality typology associated with this resilient trajectory have not been thoroughly investigated—individuals with Miller’s ‘low pathology’ PTSD are, by definition, not members of this no-pathology group.
Further limiting our understanding of the relationship between personality and posttraumatic psychopathology is that to date, personality typologies have been studied almost exclusively in individuals with chronic PTSD. This is problematic as there is accumulating evidence to suggest that expression of psychopathology such as depression and PTSD and relationships between them change over time (O'Donnell, Creamer, & Pattison, 2004) and hence the subtypes reported in chronic populations may evidence different patterns in the acute phase posttrauma. It is not known whether different personalities respond differently to trauma exposure over time. Finally, trauma-exposed populations have a significant pre-trauma history of psychopathology (O'Donnell et al., 2009), which serves as a risk factor for future diagnosis (Shalev et al., 1998; Ozer, Best, Lipsey, & Weiss, 2003) but does not entirely account for the development of posttraumatic disorders (Bryant et al., 2010). It is not yet clear whether personality typologies are is meaningfully related to posttraumatic psychopathology when the influence of pretraumatic psychopathology is also considered.
Therefore, in order to advance the field, it is critical that prospective cohort studies be conducted that examine whether and how internalizing and externalizing personality subtypes influence the development and accrual of posttraumatic psychiatric disorders, independently of pretraumatic disorder. The ability to reliably identify groups of individuals with particularly high or low risk of developing different types of posttraumatic psychopathology may have significant implications for screening and monitoring of trauma-affected individuals and service delivery planning.
To that end, this study aims to build on previous research by identifying personality typologies at the time of trauma exposure, and examining the relationship between these typologies and the development of common posttraumatic mental health disorders, including but not limited to PTSD, over the first year after trauma. Bringing together research on the general structure of psychopathology and personality typologies of trauma survivors with PTSD, we hypothesise that we will identify a group with high negative emotionality and low positive emotionality that develops internalizing disorders, and a group with high negative emotionality and low constraint that develops externalizing disorders. We also anticipate the existence of a third group that does not develop any significant psychopathology, although are unsure whether this group will display personality traits within the normal range or be protected by increased or decreased levels of particular traits. In the absence of evidence, we make no a priori assumptions about the effect of psychiatric history on the relationship between personality and posttraumatic psychopathology.
Section snippets
Participants
Consecutive admissions to a level I trauma centre in Victoria, Australia were recruited into the study between November 2011 and June 2013. Patients were approached during their acute admission and were invited to participate in the study if they were (a) admitted to the trauma service for more than 24 h following a traumatic injury, (b) aged between 18 and 65, and (c) had a good comprehension of English. Patients with moderate or severe head injury, psychosis, or whose injury was the result of
Latent profile analysis
Fit statistics for the LPA analyses are shown in Table 1. Compared to a two-class model, a three-class model provided a superior fit to the data, with a substantially lower SS-BIC value, significant BLRT (p < 0.001), and lower BIC. Looking at the four-class model, almost all fit statistics suggested a worse fit for the data than the three-class model, and the four-class model could not be replicated, suggesting that too many classes had been extracted. Thus, a three-class model was retained for
Discussion
The findings reported here extend previous research in showing that internalizing and externalizing personality typologies are of value not only in explaining patterns of comorbidity in PTSD population (e.g. Miller et al., 2003), but are also relevant to understanding the risk of disorder onset in all those who experience a traumatic event. While the influence of personality traits on posttraumatic psychopathology have been explored previously (Koffel et al., 2016), this is the first study to
Conclusions
This study built on previous research by examining the prospective relationship between personality and a range of psychiatric disorders developed over a 12 month period among those exposed to a traumatic event. It demonstrates that the risk of disorder onset across personality-based subgroups of injury survivors varies considerably. Importantly, differences in the likelihood of gaining or losing a diagnosis over time are significantly greater than would be considered given group differences in
Acknowledgements
This study was financially supported by a National Health and Medical Research Council Program Grant (568970). The authors gratefully acknowledge all the participants involved in this study.
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