**4.3 An indicator for depressive and anxiety symptoms**

The Peritraumatic Distress Inventory also predicted depressive and anxiety symptoms in the present study, although the predictive value for these symptoms was lower than that for posttraumatic symptoms. A previous study reported that posttraumatic stress disorder symptoms were a reliable predictor for depressive symptoms (Erickson et al., 2001). The Impact of Event Scale-Revised is one of the tools used most frequently for measuring posttraumatic stress symptoms; however, the it was intended to assess posttraumatic stress disorder symptoms over the previous 7 days, whereas the Peritraumatic Distress Inventory can be used immediately after motor vehicle accident. Given our findings, the Peritraumatic Distress Inventory seems to be a useful indicator not only for posttraumatic stress disorder but also major depression or other anxiety disorders.

#### **4.4 Two Peritraumatic Distress Inventory items showed high predictive values**

Items 1 and 11 of the Peritraumatic Distress Inventory showed higher predictive values for both posttraumatic stress and depressive and anxiety symptoms than other items. Item 1 inquires about helplessness. The author and colleagues previously discussed that nondrivers (passengers, bicyclists, or pedestrians) might be susceptible to subsequent posttraumatic stress disorder and other psychiatric morbidity (Matsuoka et al., 2008). Loss of control in a motor vehicle accident is suggested to be an important risk factor. Regarding item 11, some studies showed that high heart rate shortly after a motor vehicle accident is a predictor for later posttraumatic stress disorder (Bryant et al., 2000; Shalev et al., 1998; Zatzick et al., 2005), although other studies reported that heart rate was not an independent predictor (Buckley et al., 2004; Kraemer et al., 2008) and a review indicated that it cannot be accurately used to identify individuals who are at high risk for later posttraumatic stress

Peritraumatic Distress in Accident Survivors: An Indicator for

**5. Future directions**

event.

**5.1 Consolidation of fear memory** 

Posttraumatic Stress, Depressive and Anxiety Symptoms, and Posttraumatic Growth 105

Fear memory, which is the important component of peritraumatic distress, has attracted considerable attention especially preclinically. An excellent review by Ressler & Mayberg (2007) has demonstrated that memories do not immediately become permanent at the time of initial experience but exist in a labile state for at least a period of hours and possibly days, during which time they become consolidated into more permanent memory. During this consolidation, molecular, synaptic, neurotransmitter, and system-level changes occur consecutively (McGaugh, 2000). The neural circuitry implicated in fear memory likely involves complex interactions between the hippocampus, the amygdala, and the medial prefrontal cortex (Nemeroff et al., 2006). Because the hippocampus processes and temporarily stores new memory before transferring labile memory to the cortex for permanent storage (Feng et al., 2001), it may be possible to modulate the consolidation of

A previous study showed that exercise on a running wheel, which promotes neurogenesis, increased the rate of loss of hippocampus-dependent contextual fear memory (Kitamura et al., 2009). The study suggested that the level of hippocampal neurogenesis could be modulated and was associated with a causal relationship between adult neurogenesis and the hippocampus-dependent period of fear memory. It is theoretically possible, therefore, that promoting adult neurogenesis early in the transition period might facilitate the clearance of fear memory from the hippocampus. Modulating memory consolidation would mean that posttraumatic stress disorder could be prevented in the aftermath of a traumatic

Fear consolidation can be blocked by an antagonist of noradrenergic activation, and the effectiveness of beta blockers for secondary prevention of posttraumatic stress disorder has been studied in clinical trials (Pitman et al., 2002; Vaiva et al., 2003). However, as traumatized individuals are not psychiatric patients, daily life-based intervention for the

Based on the animal research conducted to date, omega-3 fatty acids are the most promising candidate for dietary intervention in the aftermath of a traumatic event to facilitate adult hippocampal neurogenesis (Beltz, 2007; Calderon & Kim, 2004; Kawakita et al., 2006; Wu et al., 2004, 2008). The possible effects of omega-3 fatty acids on brain structures have also been observed clinically: a significant correlation was found between omega-3 fatty acid consumption and gray matter volume of the amygdala, hippocampus, and anterior cingulated gyrus in healthy adults (Conklin et al., 2007). Conversely, a selective deficit of docosahexaenoic acid was reported in the postmortem frontal cortex of patients with depressive disorder (McNamara et al., 2007). Following discussion of these results in the literature, Matsuoka proposed that promoting hippocampal neurogenesis by omega-3 fatty acid supplementation after trauma could reduce subsequent posttraumatic stress disorder

new fear memories while they are being formed (Pitman & Delahanty, 2005) .

**5.2 Role of hippocampal neurogenesis in memory consolidation** 

**5.3 Omega-3 fatty acids and hippocampal neurogenesis**

prevention of posttraumatic stress disorder is preferable.

symptoms (Matsuoka, 2011).

disorder (Bryant, 2006). To ask if survivors felt any physical reactions might be a better alternative to predict subsequent psychiatric morbidity.

#### **4.5 An indicator for posttraumatic growth**

The present results also suggested that the Peritraumatic Distress Inventory could predict posttraumatic growth, especially the 3 aspects of appreciation of life, spiritual change, and relating to others at 18 months after the accident. Multivariate regression analysis was not used to examine the predictive value of the Peritraumatic Distress Inventory for the Posttraumatic Growth Inventory because predictors for posttraumatic growth are not well established and our sample size was modest; however, the result was consistent with that of previous studies. According to Janoff-Balman, these 3 subscales can best be understood as existential reevaluation (Janoff-Bulman, 2004), and a previous study showed that they had a positive association with posttraumatic stress disorder (Taku et al., 2007). The author and colleagues also showed that appreciation of life and spiritual change were positively correlated with posttraumatic stress disorder symptoms, which can be regarded as signifying coping effort in the face of enduring distress, rather than an outcome of coping success (Nishi, Matsuoka and Kim, 2010). The predictive value of the Peritraumatic Distress Inventory for appreciation of life was quite high in the present study, so managing peritraumatic distress may need specific coping efforts. This would point to the importance of clinicians and researchers identifying and being attentive to the survivor's own meanings and interpretations.

#### **4.6 The potential use of the Peritraumatic Distress Inventory in emergency departments**

The author and colleagues previously showed that a cut-off score of 23 on the Peritraumatic Distress Inventory maximized the balance between sensitivity (77%) and specificity (82%) (Nishi, Matsuoka, Yonemoto et al., 2010). Further investigation is required to determine its adequate usage bearing in mind its low positive predictive value (53%). However, the early identification of motor vehicle accident survivors who appear not to be at risk of developing posttraumatic stress disorder is one potential use of the Peritraumatic Distress Inventory because of its high negative predictive value (93%). Given the typical limits on the psychiatric resources available, the Peritraumatic Distress Inventory would likely be a useful indicator for posttraumatic stress disorder and psychiatric morbidity in emergency departments.

#### **4.7 Limitations**

This study has some limitations. Firstly, the sample size was modest. Secondly, the attrition rate was relatively high, although the patients who dropped out were not significantly different from those who participated in the follow-up assessments in terms of the Peritraumatic Distress Inventory and other covariates. In an earlier publication, we revealed that the factors of being male, unconscious during MVA, low cooperativeness, and less severe injuries were significant predictors of dropout (Nishi et al., 2008). Participants with less severe injuries did not need to come to the National Disaster Medical Center for treatment after discharge which might have affected the attrition rate. Also, those with low cooperativeness might have been reluctant to continue participating in the study.
