Trait Theory and PTSD: Questions at the Intersect
While the effects of life trauma on the individual are an advancing area of psychological study, the point of intersection of PTSD and personality is not yet well understood. Recent research is beginning to shed light on the neurobiological mechanics of the brain in regard to PTSD, but there is still much to learn. Further, there may be certain personality traits that can predict, to some degree, which individuals are at risk for post trauma symptom development. A logical continuation of study would be to ascertain the functional and neurobiological impacts of critical traumatic events on developing traits in children and existing traits in adults. Such information could then bear the fruit of development of mitigating therapies and habilitation of damaged traits.
Trait Theory and PTSD: Questions at the Intersect
All psychological theory and investigatory research has its greatest value when it can be translated into practical means of advancing understanding and knowledge. Indeed, research in psychology that does not have practical implications or lead to the development of real world tools to help people is essentially just an academic exercise. Therefore, the value of the extensive research on personality and in particular, trait studies, has value not only in articulating descriptions of what the norm and averages are for human personality expression, but as use as a baseline tool to discern aberrations in personality that can benefit from professional intervention.
This paper sets out to investigate the intersection of personality trait theory and Post Traumatic Stress Disorder. In order to do this, an examination of if and how traits change, a review of what is already understood about the connection between traits and PTSD, some specific trauma study examples, and then on to some important neurobiological findings. Finally, directions for further research will be taken up.
Trait Stability and Change
In the field of psychology, personality and psychological disorder have been entwined studies from the time of Freud. In fact, one can easily view pathology as the midwife of psychology. Freud’s study of the disordered individual naturally gave rise to research regarding the baseline norm of personality on which to compare and contrast pathology. The need for an understanding of the coherence of the person pushed the study of personality forward to the current and popularized “Big Five” and approach to personality. Yet this set of descriptors has clear flaws in application to those individuals who have had life experiences that do not fit neatly into such a grand theory of personality.
Personality theorists have long debated the question of trait stability over the lifespan. It would stand to reason, from a simple review of psychology back to the times of Freud, that there is an implicit acceptance in psychology that life experience, in particular, traumatic experience, can profoundly alter personality. From Freud’s work with female, and allegedly sexually abused ‘hysterics’ to the initial and rudimentary diagnosis of ‘shell shock’ in the First World War, intense, traumatic experience has been understood to alter an individual in dramatic ways. A primary heuristic can be developed: once PTSD has developed, does it serve to alter the personality in such a way that the PTSD is no longer an effect ‘layered onto’ personality, or does it fundamentally alter personality traits? This in turn suggests the question: how stable are personality traits while under insult?
Different statistical measures in multiple research efforts have revealed that in fact, traits both remain quite stable, and change over time (Berry & Jobe, 2002). It was once assumed in the study of personality that traits became ensconced at a fairly young age. A study by Roberts and Morczek (2008) demonstrated that there are specific trait changes in such areas as warmth and self-confidence in the age ranges of 20-40 years, and traits are able to change at any age in association with continuing personal development. The reference to continuing personal development becomes significant to our discussion because many victims of PTSD are victims of interpersonal abuse at the hands of adults.
This ability for traits to change over a time period appears to extend to those individuals whom have identified Axis II mental health disorders. In a study concerning the stability of personality traits in relation to four specific personality disorders, changes in traits and the disorders were consistent (Warner, et al., 2004). This would seem to demonstrate an intimate connectivity between personality trait and personality disorder, possibly in some symbiotic fashion. The implication, of course, is that there may be various kinds of linkage between fundamental personality traits and mental health symptom ‘traits’. In the circumstance of an individual involved in a traumatic event, it stands to reason that ‘trauma’ indicates a rather catastrophic and global effect, much like the effects (not source) of an Axis II personality disorder.
Specific trait change over time can be seen in a large study by Mroczek and Spiro (2003) looking at personality trait trajectories over the course of twelve years in a group of 1,600 men with extraversion and neuroticism as key traits. They found clear changes in both traits, citing that the ‘extroversion trajectory best defined by a linear model, but neuroticism was characterized by quadratic decline with age” (Mroczek & Spiro, 2003). Life events related to age, such as the death of a spouse was demonstrated as a significant predictor of changes in traits. This suggests that there are specific aspects of chronological age, as well as life experience that may serve to alter traits to some varying degree. If age and life experience impact the trajectory of elderly men’s trait stability, might it also not function to do the same for children, teens, and young adults, especially if those experiences are traumatic? If age and experience have the ability to effect change in trait, how exactly does this happen, and to what degree do each have weight and how the two interact are especially pertinent to cases of young children who are maltreated.
Childhood ‘temperaments’ are quite often referred to in personality literature as something less than full-fledged traits. The idea is that temperaments, along with the child’s development, go through several transformative progressions in the child’s environs towards a more stable and clarified adult trait (Roberts & DelVecchio, 2000). This begs the question: how much more malleable are childhood teperaments than adult traits? If this were so, it would have strong implications for not only the acquisition of stress symptoms and stress disorders in children, but indications for early and aggressive treatment as well. Malleability may suggest either a vulnerability that would provide a weaving effect of the PTSD symptoms into the emerging traits of the child, or the possibility of an easy ‘wiping of the slate’ removal of trauma symptoms. Still yet, individual differences in personality profile may be a variable that would make one outcome more statistically likely than the other.
Temperament might be viewed as a foundational structure based in psychobiological truths; the progression towards adult traits is layered over time and is impacted by environmental dynamics (Caspi, 1998). This view of a highly dynamic process, which has an intuitive correctness about it, gives room for multiple kinds and sources of incidental or intentional life experience variables to shape personality. Caspi’s approach appears to leave ample room not only for the average personality narrative, but for the aberrant as well. One significant aspect of Caspi’s view in relation to the post trauma victim is the victim’s ultimate gathering of a narrative and need for a sense of continuity beyond the critical incident as a way of explaining to themselves (and possibly others) just how core aspects of themselves (read central traits) have changed as a result of the bad things that have happened to them. Since critical incidents that create trauma are inherently environmental, the myriad of environmental variables (and their relative impact) involved in trauma only add to the complexity of the current challenge.
There appears to be a historical development of tension between the mass of research on the side of the “Big Five” factors as a grand personality theory, and the relatively newer narrative type theories such as Social Investment theory. The former asserts that personality develops primarily from a genetic perspective, while Social Investment, for example, states that social roles are more shaping of personality. Some studies show a decline in support for the Big Five and growing support for narrative explanations (Wood & Smith, 1999). While new developments in exploration of personality development are desired and interesting, continued and repeated research to demonstrate the validity of such assertions as the narrative approaches are clearly needed to avoid the well known bias of ‘out with the old, in with the new’. The ‘Big Five’ continue to have important contributions to personality understanding, and still have potential to inform the intersection of personality and trauma, as will be demonstrated.
While narrative approaches to explaining personality are exciting and show great promise, it is important not to cast away our original question of continuity and change over the lifespan. Caspi, in an important study of five questions related to continuity and change, asserts that there are qualities of personality that continue from childhood through adulthood that do not become ‘set in stone’. The study also reinforces the important aspects of environment, and that over time; individuals gain greater skills (thus increased personality consistency) in coping with their environment (Caspi, 2001). The addition of environment to the conversation of personality development and continuity opens a wide area of interest in relation to trauma, as trauma often alters the environment (in this sense not only the literal living environment, but internal, psycho-emotional environment) of the victim to a significant degree.
McAdams and a large group of professional cohorts put narrative explanations of personality to the continuity-over-time test in a 2006 study with results that demonstrated continuity and provided sound reasoning for noted changes in the individual (McAdams, et al., 2006). Narrative approaches clearly have important perspectives to offer personality study in general, and in particular, seem to be a logical fit for use in approaching the issue of the effects of PTSD on personality trajectories in both children and adults. Caspi and Moffitt (1993) assert that an important possible temporal study period for individual personality changes would be during environmental change for the individual, as this would allow the observer to closely examine the “mechanisms” of personality. While it would clearly be unethical for a professional observer to simply stand by while an individual is experiencing an environment of trauma, the individual certainly could be closely observed in a very short time period following the critical events. In the same study, Caspi and Moffitt unintentionally again speak to the PTSD intersection when they cite that:
“Systematic change is likely to occur during transitions into new situations, when there is a press to behave and when previous responses are actively discouraged while clear information is provided about how to behave adaptively” (Caspi & Moffitt, 1993).
For example, interpersonal trauma, by obvious definition, is an intense transition into a new situation that includes a strong press to behave in some responsive or perhaps more accurately, adaptive fashion. Once the trauma ceases, the victim’s entire life response pattern is altered and certain responses are discouraged by social pressure or the perpetrator; the perpetrator may also instruct the victim on how to behave adaptively to the post trauma or ongoing trauma phase.
It is perhaps a curious fact that a traditional approach to the treatment of PTSD in adults is for the victim to create a narrative about the critical incident that is shared with the therapist and then repeated multiple times until the incident becomes ‘normalized’, or integrated to such a degree that the event loses its traumatic intensity. The efficacy of this treatment, not being a matter of study here, still evokes the question: should the acute symptoms of PTSD be relieved, are there still fundamental personality changes as a result? Just because the individual may learn an adaptive response, such as the ability to appear to be coping with the trauma, it does not mean that the symptoms are truly in remission, or that fundamental changes have not occurred.
Traits and PTSD
There is no question about the power of trauma to alter an individual’s life, but why trauma may profoundly impact one individual for years, and not affect another individual for more than a few weeks is not yet clearly defined (Koenne, 2006). Existing research does demonstrate that there are some traits that seem to serve as possible predicting tools to PTSD development (Knezevic, Opacic, Savic, & Priebe, 2005). In a prospective study using rookie firefighters, high levels of hostility and low levels of self efficacy were shown to be predictors of increased measures of PTSD symptoms after two years of firefighting experience (Heinrichs, et al., 2005).
In an assessment of risk factors for the outcome of PTSD, Lecic-Tosevksi, Gavrilovic, Knezevic, and Pribe (2003) ascertained through the use of established stress evaluation tools that compulsivity and passive-aggression correlated with the level of stress intrusion symptoms in victims of an air attack, and those with avoidant personality traits to begin with had a higher degree of symptoms in the avoidant symptom cluster for PTSD.
Neuroticism is often strongly associated with PTSD symptom development (Cox, McPherson, Enns, and Williams, 2004.) In one study, the level, or intensity of neuroticism directly correlated with the intensity of subsequent stress symptomology (Lauterbach & Vrana, 2001). The question is, of course, can neuroticism be seen as a reliable predictor of PTSD? At least one study took up this challenge, and determined that neuroticism did not predict increases in post trauma symptoms, but may have discovered indications that PTSD symptoms may somehow draw from an existing neurotic pool (Engelhard, van der Hout, and Kindt, 2003).
Such ‘predicting traits’ are of little value to the average population set as a practical treatment tool, since traumatic events, by their nature, are quite difficult to predict. Looked at another way, the knowledge that those with PTSD may be high in particular traits could be a useful tool to focus treatment for the field clinician charged with treating such victims. Closer evaluation and articulation of childhood temperament-to-trait mechanics, as well as specific vulnerabilities would be productive in formulation of child specific treatments to keep Acute Stress from developing into Post Traumatic Stress.
The other four of the “Big Five” traits make an appearance in a study of post trauma symptoms in burn victims; in addition to being high in neuroticism, the victims were also found to be high in extraversion, and were lower in openness, agreeableness, and conscientiousness compared to a presumably non-burned sample (Faurbach, Lawrence, Schmidt, Munster & Costa).Though this study appears to be straight forward and indicative of a change in traits related to the specific trauma of being burned, there can be criticism brought to bear on the basis of wanting to know more about the variables that may impact burn victims.
Comorbid conditions associated with PTSD often fall into the Axis II categories, in particular such personality disorders such as borderline, narcissistic, and schizotypal (Lauterbach, 2001). A Russian study of juvenile delinquents associated PTSD with behavior inhibition, high harm avoidance, and low self-directedness (Ruchkin, Schwab-Stone, Koposov, Vermeiren, & Steiner, 2002). It is quite logical to consider that such personality disorders and characteristics may produce vulnerability not only to post traumatic symptoms, but also to conditions and environments that place the individual at risk for trauma. This supposition is pertinent because it reinforces that pre-existing personality characteristics/traits can pre-dispose an individual to acquiring PTSD: if personality disorder is linked to PTSD, why not traits?
It is intuitive that trait, life experience, particular environments, and subsequent adaptations result in a synergistic mix that produces some end result that will look qualitatively and quantitatively different depending on variables. Evidence can be shown that traits considered as possible vulnerabilities to stress disorder development, along with a history of previous stressful events and the particulars of a critical event may combine not in an additive fashion, but work in a dynamic interaction to produce the final PTSD diagnosis (Lecic-Tosevski, et al., 2003). It is these multiple points of synergy, or intersects that perk interest; discovery of the nature and mechanics of the points of change have profound implications for early intervention and subsequent longer term treatment of stress disorders. In order to explore this direction, a broad range of experience and environments of trauma need to be assessed, with trait as the binding thread of discovery.
Some Specific Examples
There have been many studies making use of survivors of wars in relations to traumatic stress disorder. While these types of studies are by necessity largely retrospective, they can offer hints about the possible mechanics and circumstances of just how a personality traits may be altered. In a study concerning victims of war that were displaced inside Bosnia as compared to individuals who became refugees and were forced out of the country, those who were forced out scored higher on trauma scales (Hunt & Gakenyi, 2005). Once again, there are undoubtedly multiple variables between the two groups that would provide interesting scrutiny, but the different experience of each group, not to mention literal environment difference in relation to outcome is impressive. Another war study concluded that traumatic events tend to instigate cognitive changes in the way an individual views the world, and this in turn leaves them vulnerable to an increased neuroticism (Bramsen, van der Ploeg, van der Kamp, & Ader, 2002). In effect, the individual who is high in neuroticism becomes vulnerable to PTSD when exposed to trauma, the trauma, in turn verifies the individual’s neurotic approach to life, thus increasing neuroticism and post trauma symptoms. This is the proverbial dog chasing his own tail.
War trauma may or may not have strong interpersonal aspects to it, depending on if the trauma was up close and interpersonal such as torture, or impersonal, as in carpet bombings. The interpersonal trauma of child abuse is often compared to war and torture trauma in the effects it produces. Extended periods of torture and early childhood trauma experiences appear to produce damage to the formation of personality primarily magnifying weaknesses in behavioral, affective, and cognitive aspects of the individual (Daud, af Klinteberg, & Rydelius, 2008). In still another comparison using the Disorders of Extreme Stress tool, it was found that survivors of genocide had fewer personality changes related to that trauma than did adults who experienced lengthy childhood traumas (Weine, et al.). Clearly, interpersonal trauma has a set of aspects to it that are qualitatively powerful, as or more powerful than other forms of trauma.
Interestingly, there is some indication that the long range power and impact of early trauma is quite durable over time. A study of three groups of women who had suffered sexual trauma, one group as children, one group as adults, and one group who had experienced both, yielded results indicating that the women who had suffered childhood sexual trauma scored highest in personality disturbance, but the group who had experienced both childhood and adult sexual trauma were not significantly different (Wonderlich, et al.).
Self reports by adults who have been abused show a reliable relationship between the abuse and later adult trauma symptoms (Briere and Ellitott, 2003). In contrast to the aforementioned and oftentimes criticized self-report, difficulties in self-esteem in adulthood are consistently related in meta-analyses to childhood sexual abuse (Jumper, 1995). There is a legitimate question that arises surrounding the durability of PTSD symptoms for different types of natural disaster type trauma, war trauma, and of child maltreatment. More study is in order to discover if in fact there are substantial differences not only in the source, but profiles of stress symptomology for different kinds of critical events.
Particular developmental periods in an individual’s life may provide increased vulnerability to critical incidents. As a child grows, the rather complex neurobiological stress mediating process is also developing; if it is altered by a trauma, this can effect the functional capabilities of stress regulation in adulthood ( Perry, 1994). It is commonly stated that children are quite resilient, but along with aspects of resilience, there also appears to be a great deal of malleability that can result in significant functioning alterations. If there are noted long lasting effects in adulthood, it is reasonable to hypothesize that some fundamental change certainly has taken place at some integration point in the child’s personality.
It is also reasonable to question that that the kind of trauma experienced may not be as important to the sustainability of alterations in personality as the age at which the trauma occurred. Survivors of childhood cancers demonstrate a relatively high degree of somatization, trauma type issues and actual PTSD (Erickson, 1999). There appears to be multiple sign posts pointing to a key intersect between the neurobiological mechanism of PTSD and personality in the holistic sense, if not in the more detailed trait arena.
Traits, PTSD, and Neurobiology
The acute interest in the intersect between PTSD and trait development or trait alteration, while an interesting area of learning in its own right, has important implications for a wide variety of areas. Neurobiological understandings could direct the way to research on medications specifically for PTSD. Genetic research could hold hope for discovery of specific genes related to at risk individuals, or even gene alteration for treatment purposes. In cases of interpersonal trauma, proofs that PTSD may damage an individual’s core personality structure could have multiple legal implications for damages and proceedings to remove children from contact with abusers. The intersection between mental health disorders, personality traits, and neurobiology is clearly just beginning as a research journey, and does not yet have definitive answers to the many questions that arise. In a perusal of the neurobiological dimensional models of Cloninger, Depue, and Siever, Paris (2005) determines that while the models lend assistance to the discovery of significance, they lack empirical support for clear understanding of the connection between traits, disorders, and known neurotransmitter systemics. But other researchers appear to be making gains in understandings with some broader studies regarding this intersection. For example, serotonin may serve to block aggression, and encourage pro-social behavior that encourages affiliation (Young and Moskowitz, 2005). It also appears to positively correlate as an inhibitor over both positive and negative affective behaviors (Zald and Depue, 2001).
Evidence is emerging for a neurobiological linkage between personality and disorders such as depression (Foster and MacQueen, 2008). While it has long been anecdotally known that depression acts to alter affect and mood, the efficacy of the newer SSRI medications has made it evident that there must be a kind of ‘layering’ effect of the depressive illness over top of the organized personality; that is, they are separate entities. Just how the depression and personality interact in the closed environment of the individual’s unique physiology is still a deep question.
Using a ‘psychobiological threshold model’ has been able to explain differences in dopamine transmission related to behavior and traits (Depue and Collins, 1999). Animal studies and some human studies have found evidence connecting the traits of extraversion, neuroticism, and psychoticism to dopamine, norepinephrine, and serotonin (Depue, 1995). These are admittedly very broad personality traits, but if repeated experimental models are able to verify and establish reliability of such results, this can open the way for more detailed understandings.
The primary brain structures that work to regulate stress, the hypothalamic-pituitary-adrenal axis (HPA), is key in emotions such as depression, anxiety, and aggression, as well as cognitive functions such as memory and learning. Dysregulation of the HPA axis resulting from abuse in children is now a strongly indicated (Scarpa,2004). Adults who survive child abuse have been shown to have altered pistuitary-adreanal effects (Heim, Bonsall, Miller, & Meneroff, 2001). Further, HPA dysregulation in children with PTSD is evidenced by significant indications of urinary-free cortisol (DeBellis, 1999). Startlingly, there have been demonstrations of significantly smaller brain size and abnormal cortex development in neglected children who were otherwise healthy (Perry and Pollard, 1997).
These realities of HPA dysregulation in PTSD victims, and the fact that symptoms gained in maltreated children can still persist into adulthood would appear to cloud a cut-and-dried view of some personality approaches. Perhaps in the future, PTSD may be considered by the DSM to fit more into an Axis II personality disorder classification, especially if the PTSD was acquired at a young age, and the symptoms persists strongly into adulthood.
In young children or infants, trauma induced psychobiological changes have profound effect on the limbic system, which regulates emotional states. These states then impact affect, cognition and behavior in ways that become stylized ways of coping and regulating stress (Schore, 2001). Emotional states are certainly an essential component of personality, as is the ability to moderate intense emotions as translated into behavior. There are indications that a child’s brain development organizes around patterns of affective experiences, and stress may alter the brain development by changes in neurogenesis, migration, synaptogenesis, and neurochemical differentiation (Perry, 1996). Symptom development is related directly to how the individual responds during the critical incident; the adaptive responses to the stress and the intensity and duration of the responses are also keys. As the adaptive/threat response is prolonged, there is an increase in long term symptoms (Perry, 1996). This indicates that there is a possibility that even if further trauma is not experienced by the individual beyond the initial life altering event, their repetitive symptom set can itself continue the damage process.
The previous concepts certainly do bear the flavor of a macro-view of what a personality trait is: impacted by environment and experience, rooted in neurobiology, shaped by learning and adaptation, and demonstrated in cognition and behavior. Intense, traumatic life stressors are essentially fundamental personality trait shapers.
Directions for Further Research
From the efforts of this literature perusal, there appear to be several key points that would be helpful for further research. A more detailed examination of the intersection between personality trait and intense, critical incidents is in order to suggest means and methods of prevention and treatment. The function of age would appear to be an important variable in the possible impact of high stress on personality, as does the particular type, quality, and duration of stressors. If PTSD at a particular age has the ability to alter personality has far reaching implications for legal issues of child maltreatment and wider ranging public policy.
While certain personality traits from the “Big Five” have been shown to be useful predictors of PTSD development, further study on why and how this is so, as well as if the same traits are altered significantly by PTSD is a practical clinical question. Environmental factors, including not only the environment of the critical incident, but the individuals’ environment prior to and following the PTSD creating event would be an additional rich area of work; especially if manipulation of post-trauma environment proves to be a helpful tool in mitigating symptoms.
It seems clear that PTSD has the power to alter personality traits at any age, but most likely has a greater influence during the malleable pre-teen years. Research to confirm this would be useful at a heuristic as well as practical level. Does PTSD permanently alter personality is a question that blurs the line concerning the diagnosis of PTSD as an Axis I diagnosis towards a personality disorder, Axis II direction.
The neurobiological and genetic aspects of personality and PTSD hold promise of discovery of the ability to mitigate damages to personality from PTSD. A fuller understanding of neurological damage mechanisms, routes, and possible re-routing and repair may give direction to new and innovative non-biologically intrusive psychotherapy techniques. More complete understanding of brain and brain chemistry effects on personality development and alterations due to trauma can also give rise to research in pharmaceutical and gene repair treatments to mitigate the personality and life altering effects of PTSD.
Berry, Jane M., & Jobe, Jared B. (2202). At the intersection of personality and adult development. Journal of Research in Personality, Vol. 36, Issue 4, 238-286.
Perry, B.D. (2001b). The neurodevelopmental impact of violence in childhood. In Schetky D & Benedek, E. (Eds.) Textbook of child andadolescent forensic psychiatry. Washington, D.C.: American Psychiatric Press, Inc. (221-238)
Briere, J., & Elliott, D. (2003). Prevalenct and psychological sequelae of self-reported childhood physical and sexual abuse in a general population of men and women. Child Abuse & Neglect, 27; 1205-1222.
Caspi, Avshalom. (1998). Personality across the life course. W. Damon (Ed.) Handboolk of Child Psychology (5th Ed.). Vol. 3 Social, Emotional, and Personality Development. (pp 311-388). New York: John Wiley and Sons.
Caspi, Avshalom, & Moffitt, Terrie E. (1993). When do individual differences matter? A
paradoxical theory of personality coherence. Psychological Inquiry, Vol. 4, No. 4, 247-271.
Caspi, Avshalom, Roberts, Brent W. (2001). Personality development across the life course: the argument for change and continuity. Psychological Inquiry, Vol. 12, No. 2, 49-66.
Cox, Brian J., MacPherson, Paula S.R., Enns, Murray W., and McWilliams, Lachlan A. (2004). Neuroticism and self-criticism associated with posttraumatic stress disorder in a nationally representative sample. Behavior Research and Therapy. Vol. 42, Issue 1, 105-114.
Daud, Atia, afKlinteberg, Britt, and Rydelius, Per-Anders. (2008). Trauma, PTSD and personality: the relationship between prolonged traumatization and personality impairments. Scandinavian Jounral of Caring Sciences.
DeBellis, Michale D. (1999). Developmental truamatology: neurological development in maltreated children with PTSD. Child Maltreatment, September 1999, Vol. XVI, Issue 9.
Depue, Richard A., & Collins, Paul F. (1999). Neurobiology of the structure of personality: dopamine, facilitation of incentive motivation, and extraversion. Behavioral and Brain Sciences, 22;491-569.
Depue, Richard A. (1995). Neurobiological factors in personality and depression. European Journal of Personality, Vol. 9, Issue 5, 413-439.
Englehard, Iris M., van den Hout, Marcel A., Kindt, Merel. (2003). The relationship between neuroticism, pre-traumatic stress, and post-traumatic stress: a prospective study. Personality and Individual Differences. Vol. 35, Issue 2, 381-388.
Erickson, Sarah. (1999). Somatization as an indicator of trauma adaptation in long-term pediatric cancer survivors. Clinical Child Psychology and Psychiatry, Vol. 4, No. 3, 415-426.
Fauerbach, James A., Lawrence, John W., Schmidt, Chester W., Munster, Andrew M., and Costa, Paul T. (2000) Personality predictors of injury related posttraumatic stress disorder. Journal of Nervous &Mental Disease. 188(8):510-517.
Foster, Jane A., & MacQueen, Glenda. 2008. Neurobiological factors linking personality traits and major depression. Canadian Journal of Psychiatry, 53(1):6-13.
Heim, C., Newport, J., Bonsall, R., Miller, A., & Meneroff, C. (2001). Altered pituitary-adrenal axis responses to provocative challenge tests in adult survivors of child abuse. American Journal of Psychiatry, 158:575-581, April, 2001.
Heinrivh, Markus, Wagner, dieter, Schoch, Walter, Soravia, Leila M., Hellhammer, Dirk H., and Ehlert, Ulrike. (2005). Predicting posttraumatic stress symptoms form pretraumatic stress risk factors: a 2- year prospective follow-up study in firefighters. American Journal of Psychiatry, 162:2276-2286.
Hunt, Nigel, & Gakenyi, Maha. (2005). Comparing refugee and nonrefugees: the Bosnian experience. Journal of Anxiety Disorders. Vol. 19, Issue 6, 717-723.
Jumper, S.A. (1995). A meta-analysis of the relationship of child sexual abuse to adult psychological adjustment. Child Abuse and Neglect, 19, 715-728.
Kagan, J. (2000). Temprament. In A. Kazdin (Ed.), Encyclopedia of Psychology. New York: Oxford University Press.
Knezevic, Goran, Opacic, Goran, Savic, Danka, and Priebe, Stefan. (2005). Do personality traits predict post-traumatic stress: A prospective study in civilians experiencing air attacks. Psychological Medicine, 35:659-663.
Koenen, Karestan C. (2006) Self-regulation as a central mechanism. Psychobiology of Posttraumtic Stress Disorder: A Decade of Progress. Vol. 1071: 255-266.
Lauterbach, Dean. (2001). Personality profiles of trauma survivors. Traumatology, Vol. 7, No. 1.
Lauterbach, Dean, & Vrana, Scott. (2001). The relationship among personality variables, exposure to traumatic events, and severity of posttraumatic stress symptoms. Journal of Traumatic Stress, Vol. 14, No. 1, 29-45.
Lecic-Tosevski, Duscia, GAvrilovic, Jelena, Knezevic, Goran, and Priebe, Stefan. 2003. Personality factors and posttraumatic stress: associations in civilians one year after air attacks. Journal of Personality Disorders, Vol. 17, Issue 6, 537-549.
McAdams, Dan P., Bauer, Jack J., Sakaeda, April R., Anyidoho, Nana Akua, Machado, Mary Anne, Magrino-Failla, Katie, White, Katie W., and Pals, Jennifer L. (2006). Continuity and change in the life story: a longitudinal study of autobiographical memories in emerging adulthood. Journal of Personality, Vol. 74, Issue 5, 1371-1400.
Mrockek, Danile K., & Spiro, Avron. (2003). The Journals of Gerontology Series B: Psychological Sciences and Social Sciences, 58:P153-P165.
Muller, Robert, Sicoli, Lisa, and Lemieux, Kathryn. (2000). Relationship between attachment style and post traumatic stress symptomology among adults who report the experience of childhood abuse. Journal of Traumatic Stress, Vo. 13, No. 2.
Paris, Joel. (2005). Neurobiological dimensional models of personality: a review of the models of Cloninger, Depue, and Siever. Journal of Personality Disorders, Volume 19, Issue 2, 156-170.
Perry, B.D. (2001b). The neurodevelopmental impact of violence in childhood. In Schetky D & Benedek, E. (Eds.) Textbook of child and adolescent forensic psychiatry. Washington, D.C.: American Psychiatric Press, Inc. (221-238)
Perry, B.D. Neurobiological sequelae of childhood of childhood trauma: post traumatic stress disorders in children. In: Catecholamine Fundtion in Post Traumatic Stress Disorder: Emerging Concepts (M. MUrburg, Ed.) American Psychiatric Press, Washington, D.C., 253-276, 1994.
Perry, D.B., & Pollard, D. Altered brain development following global neglect in early childhood. Society For Neuroscience: Proceedings form Annual Meeting, New Orleans, 1997.
Roberts, Brent w., Mroczek, Daniel. (2008). Personality trait change in adulthood. Current Directions in Psychological Science, Vol. 17, No. 1, 31-35(5).
Roberts, Brent W., DelVecchio, Wndy F. (2000). The rank-order consistency of personality traits from childhood to old age: a quantitative review of longitudinal studies. Psychological Bulletin, Vol. 126, No. 1, 3-25.
Roberts, Brent W., Wood, Dustin, Smith, Jennifer L. (2005). Evaluating five factor theory and social investment perspectives on personality trait development. Journal of Research in Personality, 39, 166-184.
Ruchkin, Vladislav V., Schwab-Stone, Mary, Koposov, Roman, Vermeiren, Robert, and Steiner, Hans. (2002). Violence exposure, posttraumatic stress, and personality in juvenile delinquents. Journal of the American Academy of Child & Adolescent Psychiatry. 41(3):322-329.
Schore, Allan, The effects of early relational trauma on right brian development, affect regulation, & infant mental health. Infant Mental Health Journal, 2001, 22, 201-269.
Van Voorhees, Elizabeth. (2004). The effects of child maltreatment on the hypothalamic-pituitary-adrenal axis. Trauma, Violence, & Abuse, Vol. 5, No. 4, 333-352.
Warner, Megan B., Morey, Leslie C., Finch, John F., Gunderson, John G., Skodol, Andrew, Sanislow, Charles A., Shea, Tracie M., McGlashan, Thomas H., and Grilo, Carlos M. (2004). The longitudinal relationship of personality traits and disorders. Journal of Abnormal Psychology, 113:217-227.
Weine, Steven M., Becker, Daniel F., Vojvoda, Dleores, Hodzic, Emir, Sawyer, Marie, Hyman, Leslie, Laub, Dori, and McGlashan, Thomas H. Individual change after genocide in Bosnian survivors of “ethnic cleansing”: assessing personality dysfunction. Journal of Traumatic Stress, Vol. 11, No. 1, 147-153.
Wonderlich, Stephen A., Crosby, Ross D., Mitchell, James E., Thompson, Kevin, Smyth, Joshua M., Redlin, Jennifer, and Jones-Paxton, Maisley. (2001). Sexual trauma and personality: developmental vulnerability and additive effects. Journal of Personality Disorders, Vol. 15, Issue 15, 496-504.
Young, Simon N., Moskowitz, D.S. (2005). Serotonin and affiliative behavior. Behavioral and Brain Sciences, 28:367-368.
Zald, David, H., & Depue, Richard A. Serotonergic functioning correlates with positive and negative effect in psychiatrically healthy males. Personality and Individual Differences, Vol. 30, Issue 1, 71-86.