The estimated lifetime prevalence of PTSD among US adults is 7-8% (Kessler et al., 2013), while exposure to traumatic events is much higher (up to 90% of adults; Kilpatrick et al., 2013). Traumatic events are defined by the DSM-5 as “exposure to actual or threatened death, serious injury, or sexual violence” (p. 271). The most commonly reported events were unexpected death of a loved one, sexual assault, and witnessing someone being seriously harmed or killed.

Symptoms of PTSD

According to the DSM-5, for a person to receive a diagnosis of Post-Traumatic Stress Disorder (PTSD), they must meet the following 8 criteria (APA, 2013). First, as mentioned, the person must have been exposed to a traumatic or stressful event such as actual or threatened death, serious bodily harm, or sexual violence. The person may have experienced the event themselves, witnessed it happening to somebody else, or learned that a close family member or friend was exposed to a trauma (APA, 2013). Second, the person has intrusive symptoms such that they re-experience the trauma, for example through unwanted memories, nightmares, or flashbacks that are related to the traumatic event. These symptoms are not within the person’s control, which can be particularly distressing for those with PTSD.

Third, the person avoids trauma-related stimuli (e.g., thoughts, emotions, reminders) (e.g., people, places, objects). They do so in order to avoid the overwhelming fear response that arises when they are around trauma-related stimuli. For some people with PTSD, exposure to trauma-related stimuli can lead to an increase in intrusive thoughts, nightmares, or flashbacks. Some examples of things that people might avoid include certain locations, people, conversations or memories, rooms in their homes, etc.

Fourth, the person experiences negative changes in mood or cognition related to the traumatic event (e.g., inability to remember important parts of the event, exaggerated negative beliefs, negative emotions and the inability to experience positive emotions). Fifth, the person experiences significant changes in arousal and behaviour (e.g., irritability, hypervigilance, sleep disturbance) (APA, 2013). For example, it is not uncommon for individuals with PTSD to experience insomnia or to be hypervigilant to concerns about safety. This overarousal sometimes results in feeling tense, “keyed up” or on edge. It is also common for individuals with PTSD to have exaggerated startle responses, compared to people without PTSD.

Sixth, the disturbances in mood, cognition, and behaviour must occur for at least 1 month. Seventh, they must cause clinically significant distress or impairment in important areas of functioning (e.g., social, occupational). Eighth, the disturbances should not be better explained by the effects of a substance or another medical condition. In addition to making a diagnosis of PTSD, a psychologist can specify if the person also has symptoms of dissociation and/or if they have delayed expression of symptoms (i.e., full diagnostic criteria are not met until at least 6 months after the traumatic event) (APA, 2013).

The DSM-5 has separate diagnostic criteria for children 6 years and younger. Some important differences are that in young children, intrusive memories may not look the same as they do in adults. In children, intrusive memories can be expressed through repetitive play. Children can also experience less interest in play, an exaggerated startle response, and they may have extreme temper tantrums (APA, 2013).

Predictors of PTSD

Why do some individuals, when exposed to trauma, develop PTSD but others do not? In this section we will discuss just a few of the variables that influence the development of PTSD.

Genetic & Biological Risk Factors

In a review on the biological risk factors for PTSD, Yahyavi, Zarghami, and Marwah (2014) found that the risk for PTSD can begin in utero. The HPA axis, which plays an important role in the stress response, is greatly affected by early development. Maternal exposure to trauma, for example, can lead to changes in the fetal brain that disrupt gene expression. An example of this is DNA methylation, which re-programs the activity of genes and impacts a person’s response to stress by activating the sympathetic nervous system and causing dysfunction in the HPA axis (Yahyavi et al., 2014). Changes in these biological systems disrupts emotion regulation and the ability to effectively manage stress. However, there is growing consensus that genetic markers do not act in isolation but interact with environmental factors to impact a person’s vulnerability to developing PTSD (Klengel & Binder, 2015). In addition, the genetic risk factors for PTSD are complex and the biologic pathways for this disorder are not fully understood (Sharma & Ressler, 2019).

Centrality of Events

The discrepancy between the rate of trauma exposure and the rate of PTSD has led researchers to try to identify factors that increase the likelihood of developing PTSD after exposure to a trauma. One such identified factor is event centrality (Berntsen & Rubin, 2006), or how central we come to see that event to our lives, memories, and identity. The centrality of events scale (CES) was introduced by Berntsen and Rubin (2006) to measure the extent to which a memory for a trauma becomes a reference point for one’s identity, life story, and the attribution of meaning to other experiences. The CES has a full 20-item version and a short-form 7-item version. Both have high reliability and validity (Berntsen & Rubin, 2006). The CES has three factors. It measures the extent to which the individual’s traumatic memory: 1) becomes a reference point for everyday inferences; 2) represents a turning point in the individual’s life story; and 3) becomes a reference point for their personal identity. Each of these factors are positively related to PTSD (Robinaugh & McNally, 2011).

Berntsen and Rubin (2006) discussed why each factor of the CES may contribute to symptoms of PTSD. Berntsen and Robin (2006) proposed that the availability heuristic (Tversky & Kahnman, 1973) helps to explain the relationship between the first factor and PTSD. For example, if the trauma memories are highly accessible, then the individual will overestimate the frequency of traumatic events in everyday life, leading to unnecessary worries, precautions, and other traumatization symptoms (Berntsen & Rubin, 2006). The second factor was developed from research on how trauma can profoundly change a person’s outlook (Janoff-Bulman, 1989). Berntsen and Rubin (2006) proposed that symptoms of PTSD may be exacerbated when the individual focuses on aspects of their life that can be explained by referencing this turning point in the life story, while discounting aspects that defy these references (Berntsen & Rubin, 2006). Lastly, the third factor was developed from research that suggests that an individual may perceive a trauma as causally related to a stable characteristic of the self (Abramson, Seligman, & Teasdale, 1978; Berntsen & Rubin, 2006). Therefore, this factor is proposed to be related to PTSD when individuals attribute the trauma to stable negative identity characteristics (Berntsen & Rubin, 2006). Overall, research on event centrality supports the autobiographical memory model of PTSD, which purports that PTSD symptoms result from the over integration of the trauma into one’s memory, identity, and understanding of the world (Berntsen & Rubin, 2006; Rubin, Berntsen, & Bohni, 2008; Rubin, Boals, & Berntsen, 2008).

Since the construction of the centrality of events scale (Berntsen & Rubin, 2006) research has demonstrated a robust positive relationship between event centrality and PTSD for a range of trauma types and participant populations (Gehrt, Berntsen, Hoyle, & Rubin, 2018). For example, the positive relationship between event centrality and PTSD has been found for individuals exposed to child sexual abuse (Robinaugh & McNally, 2011), military combat (Brown, Antonius, Kramer, Root, & Hirst, 2010), terrorist attacks/bombings (Blix, Solberg, & Heir, 2014), physical injury or assault/abuse, illness, exposure to death, sexual assault/abuse, accidents, and natural disasters (Teale Sapach et al., 2019; Barton, Boals, & Knowles, 2013). The positive relationship between event centrality and PTSD has also been found for a range of participant samples, including community members (Rubin, Dennis, & Beckham, 2011; Ogle et al., 2014), undergraduate students (Barton et al., 2013; Berntsen & Rubin, 2006; Broadbridge, 2018; Fitzgerald, Berntsen, & Broadbridge, 2016), treatment-seeking individuals (Boals & Murrel, 2016; Silva et al., 2016), and military veterans (Brown et al., 2010). This relationship between event centrality and PTSD is also evident for adults ranging from 18 to 93 (Barton et al., 2013; Berntsen, Rubin, & Siegler, 2011; Wamser-Nanney, 2019; Ogle et al., 2013; Boals, Hayslip, Knowles, & Banks, 2012). However, there are nuances in the relationship between event centrality and PTSD for certain participant characteristics. For instance, younger adults (Boals et al., 2012) and women (Boals, 2010) are more likely to centralize a traumatic event and develop PTSD compared to older adults and men, respectively. Therefore, the difference in event centrality may help to explain the higher prevalence of PTSD in these populations (i.e., young adults and women; Van Ameringen et al., 2008).

Trauma Type & Social Support

There are certain types of trauma that have a greater impact on the development and maintenance of PTSD. Interpersonal traumatic events that are purposefully caused by other people contribute the most to PTSD risk and symptom severity. Events that occur by accident or by natural disaster have a far less impact on the risk for PTSD compared to interpersonal traumas (Charuvastra & Cloitre, 2008). There are several reasons explaining why interpersonal traumas are so powerful in increasing a person’s risk and severity of PTSD. In interpersonal traumas, the appraisal of threat tends to be higher, and people tend to experience a higher level of distress and decreased sense of safety in the world. In addition, interpersonal traumas can affect people’s ability to effectively interact with others (Charuvastra & Cloitre, 2008).

Social support before and after an exposure to a traumatic event plays an important role in determining a person’s risk and severity of PTSD (Charuvastra & Cloitre, 2008). Social support helps people to effectively regulate their emotions, which is central for recovery from PTSD. If a person is not able to effectively manage intense emotions and memories, they are more likely to re-experience traumatic events and use avoidance as a way to cope with difficult emotional experiences. Social support plays an important role throughout life. In childhood, the bond between the caregiver and child helps to establish a sense of safety and emotion regulation. Abuse during childhood is a significant risk factor for PTSD later on in life and it plays an important role in dysregulating the stress response system (Charuvastra & Cloitre, 2008).

Positive social interactions act as a protective factor against stress (Charuvastra & Cloitre, 2008). The value of social support lies in the perceived helpfulness and sense of connectedness with others. It is not the quantity of social support that is protective against PTSD, but rather it is the match between what the person needs and the type of support that is offered. Social support can decrease feelings of distress and increase safety and a sense of belonging. If a person feels isolated, ostracized, blamed, or feels unsupported by their relationships, this can contribute to the onset and severity of PTSD symptoms (Charuvastra & Cloitre, 2008). Negative relationships can reinforce the belief that the world is a place that is unsafe and harmful.

“Post-Traumatic Stress Disorder” is adapted from Abnormal Psychology by Jordan A. Cummings, used under Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.