In psychology literature, traumatic events have been widely examined in terms of their negative effects on survivors, namely posttraumatic stress and posttraumatic stress disorder. However, several studies showed that although its negative outcomes, traumatic events also produce some positive outcomes on trauma survivors. These positive outcomes have been called as posttraumatic growth.

Negative and positive psychological effects of traumatic events and the factors related to them will be examined in the following section of the current study. The findings on and the models explaining factors related to posttraumatic stress and posttraumatic growth will be examined respectively.

Posttraumatic Stress (PTS)

Individuals facing with potential traumatic events may develop some long-term severe emotional reactions and psychological problems. Posttraumatic stress disorder (PTSD) is a disorder characterized by some symptom clusters, such as re-experiencing stimuli related to the trauma; marked avoidance of stimuli associated with the trauma; and persistent arousal or increased anxiety. In DSM-5 (2013), PTSD was classified as four symptom clusters including twenty symptoms. These clusters are intrusion symptoms related to, and avoidance of stimuli associated with the traumatic event; distorted cognitions associated with the traumatic event; and increased arousal and reactivity. All these symptoms should occur in the aftermath of the traumatic event. Moreover, the symptoms are long lasting or have a delayed onset (Oltmanns & Emery, 2007). It was reported that this disorder may be especially severe or long lasting when the event is human made trauma such as torture, rape, or accidents (DSM-IV-TR, 2000). Furthermore, DSM-5 (2013) stated that the higher the intensity of the stressor; the higher the probability of developing this disorder was. Additionally, the findings of Ai, Tice, Whitsett,Ishisaka, and Chim (2007) were consistent with this finding revealing that there was a dose-response relationship between exposure to traumatic event and PTSD occurrence.

Models of PTS and PTSD

In the literature, there are several models focusing on the factors associated with posttraumatic stress following traumatic experiences. In the present study, the Multivariate Risk Factor Model (Freedy, Kilpatrick, & Resnick, 1993) and The Cognitive Model of Posttraumatic Stress Disorder (Ehlers & Clark,2000) will be presented.

The Multivariate Risk Factor Model (Freedy, Kilpatrick, & Resnick, 1993) was developed to examine the factors associated with mental health adjustment of individuals following natural disaster exposure. The model proposed that the mental health adjustment of individuals was influenced by different factors presented in three groups, namely the factors existing before (pre-disaster), the factors existing during (within-disaster), and the factors existing after (post-disaster) the event. Pre-disaster factors include demographic characteristics,mental health history, and life events. Furthermore, exposure to disaster, perception of high threat and low controllability and predictability were classified as within disaster factors. Finally, post disaster factors include acute and ongoing experiences, resource loss, and coping and social support (See Table 1).

In the Multivariate Risk Factor Model (Freedy et al., 1993) it was proposed that mental health outcomes might be either positive or negative depending on the experiences and resources of individuals. These experiences and resources have an influence on each other and form the adjustment process
following disaster.

In the present study, the Multivariate Risk Factor Model (Freedy et al.,1993) will be used in order to examine the factors associated with PTS following traffic accidents.

The Multivariate Risk Factor Model of Natural Disaster Adjustment

The Cognitive Model of Posttraumatic Stress Disorder was developed by Ehlers and Clark (2000). In their model, Ehlers and Clark (2000) suggested that individuals develop PTSD when they evaluate the trauma and its negative impacts as a threat. This threat can occur in two different aspects namely, external and internal. The external threat is characterized by a threat to safety and internal
threat is a perceived threat to self and the future.

How individuals appraise the event and its negative consequences, and how they build a memory of the event and its relation to their personal memories determine the occurrence of a threat perception.

According to this model, the sense of threat is accompanied by arousal, anxiety, intrusions, and negative emotional responses. It also leads to some behavioral and cognitive responses that aim to inhibit the threat and distress, and to reach a balanced situation. However, this process prevents some possible healthy cognitive changes and then leads to the development of PTSD (Ehlers & Clark, 2000).