Developing a Japanese Version of The Short Form of The Expanded Version of The Posttraumatic Growth Inventory (PTGI-X-SF-J): A Cross-Sectional Study

The 10-item short form of the Posttraumatic Growth Inventory (PTGI-SF) has been utilized worldwide. However, there is no Japanese version. Furthermore, the PTGI-SF does not capture a broader category of existential spiritual growth that has been incorporated in the more recent Expanded version of the PTG Inventory (PTGI-X). Thus, we developed a Japanese version of the Short Form (PTGI-X-SF-J), which reects more diverse perspectives on existential and spiritual growth.

issues. Thus, PTG can be experienced not only by the person who has directly experienced the event but also by his/her family members and those who witnessed it [2][3][4][5][6][7]. Previous studies have demonstrated that the degree of PTG is associated with posttraumatic stress disorder (PTSD) symptoms [8,9], social support [10][11][12], and coping strategies [13]. In addition, PTG could contribute to psychological distress [14], affect the functional and social dimensions of quality of life (QOL) and well-being [14,15], and moderate the relationship between PTSD symptoms and QOL [16]. Thus, it is important for healthcare professionals to accurately assess PTG perceived by persons who directly or indirectly experience a potentially traumatic or life-altering event.
The Posttraumatic Growth Inventory (PTGI) is most frequently used to assess PTG worldwide [17]. This scale consists of 21 items with a ve-factor structure: personal strength, new possibilities, relating to others, appreciation of life, and spiritual change [17]. Although the PTGI has been commonly used in research and clinical settings, one major concern is that this scale has relatively many items that may lead to physical and psychological burdens among people, especially those who are struggling with adversities, such as receiving aggressive medical treatments due to illness (e.g., cancer) or dealing with life crises (e.g., natural disasters and violence). To address this concern, the short form of the PTGI (PTGI-SF) was developed by Cann et al. [18]. It consists of 10 items with ve subscales similar to the original version. Each subscale has two items selected using factor loadings according to the structure of the original PTGI. The validity and reliability of the PTGI-SF were tested using data on 1,351 adults in the U.S.
The PTGI-SF has been translated into multiple languages such as Portuguese and Spanish, but not Japanese [19,20,21]. Thus, there is an urgent need to develop a short form of the PTGI for people whose rst language is Japanese to reduce their burdens, save time, and assess PTG among them more e ciently. Further, this development would spur more extensive research on PTG in Japan and the provision of clinical care for Japanese people with PTG.
In 2007, the Japanese version of the PTGI (PTGI-J) was developed by Taku et al. [22], and its reliability and validity were con rmed to clarify PTG experiences among Japanese people and compare them with international samples [23][24][25]. The PTGI-J has a different factor structure than the original PTGI with four instead of ve factors: personal strength, new possibilities, relating to others, and spiritual change and appreciation of life (this last factor was created by combining the two original factors: spiritual change and appreciation of life). The four-factor structure of the PTGI-J, being different from the original ve-factor structure, may be due to Japanese culture and norms, especially spirituality and religiosity. A previous study reported that Japanese undergraduate students tended not to evaluate the PTGI items, such as having a stronger religious belief, as positive changes [26]. This may be due to the fact that the majority of Japanese people do not believe in monotheism; thus, they may not share religious beliefs, norms, or culture like Western "religious" people might. In addition, many Japanese people may hold negative stereotypes on spirituality or speci c religions because of past incidences, such as terrorism and fraud by a religious cult. Another possible explanation may be the tendency of Japanese people to respect their ancestors and traditional rituals more than adhere to speci c religious beliefs [26].
To resolve these culture-speci c issues and capture more diverse perspectives of personal growth, the Posttraumatic Growth Inventory-Expanded (PTGI-X) version was developed in three countries, that is, the U.S., Japan, and Turkey; this version added four items that capture the broader contents of existential and spiritual changes [27]. These additional items of existential and spiritual change are as follows: "I have greater clarity about life's meaning"; "I feel better able to face questions about life and death"; "I feel more connected with all of existence"; and "I have a greater sense of harmony with the world." The validity and reliability of the PTGI-X were con rmed in the three countries, and later in the 10 countries [28], and it was con rmed to be useful for people with no strong religious beliefs like the Japanese [27]. Therefore, when developing a Japanese version of the short form of the PTGI, items concerning spirituality should be considered based on the PTGI-X rather than the original PTGI.
The purpose of this study was to develop a Japanese version of the Short Form of the Expanded version of the Posttraumatic Growth Inventory (PTGI-X-SF-J) and test its validity and reliability. The results of this study could contribute to minimizing burdens among Japanese respondents and assessing their PTG, including existential/spiritual change, more appropriately and e ciently.

Study design
This study included two sample groups: the rst and second samples comprised 408 and 284 Japanese university students, respectively. The rst study was conducted from April 2016 to June 2017, and the second was conducted from September 2017 to February 2019. This analysis was conducted from February 2021 to April 2021.

Participants
The rst cross-sectional study used questionnaires and was conducted among Japanese students at three universities in the metropolitan area of Japan. After explaining the purpose of the study to the students, those who agreed to participate and signed the consent form were asked to remain in their classroom and complete the questionnaires on their own pace. Of the 423 students who completed the questionnaires, data on 408 Japanese students (152 men, 255 women, and 1 other) were used for this study after excluding the data of 15 participants who answered that they had never experienced any stressful event in the past.
The second cross-sectional study also used questionnaires and was conducted as part of an international joint study on traumatic exposures and PTG [28]. A total of 642 students were recruited and asked to answer the questionnaire, of which 371 students completed the questionnaire. Finally, data on Demographics Information on age, gender, nationality, religion, and marital status was collected from the two samples.

Posttraumatic growth
The Japanese version of the PTGI-X was used to assess PTG in both samples. This scale comprises 25 items with a ve-factor structure including four new items regarding existential/spiritual changes: personal strength (four items), new possibilities ( ve items), relating to others (seven items), appreciation of life (three items), and existential/spiritual change (six items). Participants responded to each item using a six-point Likert scale ranging from 0 (I did not experience this change as a result of my crisis) to 5 (I experienced this change to a very great degree as a result of my crisis). Higher scores indicated greater PTG. Cronbach's alpha was .922 for the rst sample and .940 for the second sample.

PTSD symptoms
The PTSD Checklist for DSM-5 (PCL-5 [29,30]) was used to assess PTSD symptoms in the second sample. This scale includes 20 items with a four-factor structure: intrusions ( ve items), avoidance (two items), negative alterations in cognitions and mood (seven items), and alterations in arousal and reactivity (six items). The participants evaluated how much they were bothered by each symptom (i.e., item) using a ve-point Likert scale ranging from 0 (not at all) to 4 (extremely). Higher scores indicated more PTSD symptoms. Scores ≥ 31 indicated probable PTSD. Cronbach's alpha was .951 for the second sample.

Stressful events
In the two studies, 13 or 19 ad hoc questions were used to ask participants whether they had experienced a stressful event (13 or 19 kinds of stressful events, including natural disasters, accidents or injuries, serious illnesses, serious school or academic problems, and family issues) and the degree of their perceived stressfulness at the time it happened.

Challenge to one's assumptive world
The Japanese version of the Core Beliefs Inventory (CBI-J [31,32]) was used in the second sample to assess the degree to which one's assumptive world was shaken or challenged by his/her experienced life crisis. This scale has a one-factor structure including nine items. The participants rated the degree to which they seriously re-examined their core beliefs that were disrupted by a speci c event that they experienced on a six-point Likert scale ranging from 0 (not at all) to 5 (to a very great degree). Higher scores indicated a greater tendency to challenge one's core beliefs. Cronbach's alpha was .864 for the second sample.

Ruminative process
Page 6/20 The Japanese version of the Event-Related Rumination Inventory (ERRI-J [32,33]) was used in the second study to assess intrusive and deliberate ruminations following the occurrence of the event that the participants reported. This scale has a two-factor structure and includes 20 items. The rst factor includes 10 items that capture intrusive, automatic, and undesired ruminative thoughts (ERRI-Intrusive [ERRI-I]), and the second factor includes the remaining 10 items that capture deliberate and constructive ruminative thoughts (ERRI-Deliberate [ERRI-D]). The participants rated the frequency of each rumination on a ve-point Likert scale from 0 (not at all) to 4 (very often). Higher scores indicated more frequent rumination. Cronbach's alpha was .955 for intrusive rumination and .927 for deliberate rumination among the second sample.

Analysis
First, descriptive statistics were obtained for the demographic variables, stress levels when a stressful event occurred, and the Japanese version of the various scales, such as the PTGI-X, PCL-5, CBI, and ERRI. Next, an exploratory factor analysis (EFA) of the 25 items of the Japanese version of the PTGI-X (PTGI-X-J) was conducted using data from the rst study (i.e., 408 Japanese university students) to examine its ve-factor structure by selecting two items for each factor according to their factor loadings (i.e., two items with the highest factor loadings). Subsequently, a con rmatory factor analysis (CFA) of the 10 selected items was conducted using data from the second study (i.e., 284 Japanese students) to con rm its factor structure. The goodness of t of the data was evaluated using the degrees of freedom (χ 2 /df), goodness of t index (GFI), comparative t index (CFI), and root mean square error of approximation (RMSEA) [34]. Regarding the internal consistency (i.e., reliability) of the 10 items of the PTGI-X-SF-J, Cronbach's alphas for the total and ve subscale scores and the correlation coe cients between them were calculated using data from the second sample. In addition, intraclass correlation coe cients (ICCs) for the total score and subscale scores between the PTGI-X-J and the PTGI-X-SF-J were calculated using data from the second sample. To test the external validity of the PTGI-X-SF-J, the correlation coe cients between the total and subscale scores of the PTGI-X-SF-J and the scores of PCL-5, stress levels at the time it happened, CBI-J, and ERRI-J were calculated. IBM SPSS version 25.0 J for Windows (SPSS, Chicago, Illinois, USA) and IBM SPSS Amos version 25.0 (SPSS, Chicago, Illinois, USA) were used for statistical analyses.

Ethical considerations
The study was approved by the appropriate institutional review board. Informed consent was obtained from all participants.

Scores of the scales
The scores of the scales were also displayed in Table 1. In the rst study, the mean scores of the total PTGI-X-J and subscale scores of personal strength, new possibilities, relating to others, appreciation of life, and existential/spiritual change were 46.0 (SD = 24.6), 7.7 (SD = 5.6), 11.4 (SD = 7.1), 14.0 (SD = 8.6), 6.4 (SD = 3.9), and 6.8 (SD = 6.0), respectively. The most common stressful events experienced by participants were serious school/academic problems (27.0%), romantic relationship problems (13.2%), and friendship problems (12.5%). The mean score of participants' perceived stress for a selected event was 6.0 (SD = 1.1).
In the second study, the mean total PTGI-X

Exploratory factor analysis
The results of the EFA using the 25 items of the PTGI-X-J showed a ve-factor structure similar to the original version of the PTGI-X (Table 2). Of the 25 items assigned to either factor, the two items with the highest factor loadings in each factor were selected. The factor loadings of the selected items ranged from .491 to .794.

Con rmatory factor analysis
By using the second sample, CFA was performed using 10 items selected by the EFA. The results showed that the model with the ve-factor structure using two items for each factor tted the data well: χ2/df = 1.64, GFI = .971, CFI = .985, = .936, and RMSEA = .047 (Fig. 1). The factor loadings of the 10 selected items ranged from .65 to .86.

Reliability
Regarding the internal consistency of the PTGI-X-SF-J using the 10 items, Cronbach's alpha for the total score was .875. For the subscales, Cronbach's alpha was .678 for personal strength, .807 for new possibilities, .707 for relating to others, .753 for appreciation of life, and .671 for existential/spiritual change.
The correlation coe cients between the total score and the subscale scores of the PTGI-X-SF-J ranged from .404 to .794, indicating moderate to high and positive correlations between them (Table 3). The ICC for the total score between the PTGI-X-J and the PTGI-X-SF-J was .821. The ICCs for the subscale scores between the PTGI-X-J and the PTGI-X-SF-J were .863 for personal strength, .825 for new possibilities, .699 for relating to others, .949 for appreciation of life, and .728 for existential/spiritual change.

Validity
Regarding the external validity of the PTGI-X-SF-J, the variables signi cantly correlated with the total score of the PTGI-X-SF-J were the scores of the CBI and ERRI-D. The score of the rst factor "appreciation of life" was signi cantly correlated with the scores of the stress levels and ERRI-D. The score of the second factor "new possibilities" was signi cantly correlated with the scores of CBI, ERRI-I, and ERRI-D. The score of the third factor "personal strength" was signi cantly correlated with the scores of the CBI and ERRI-D. The score of the fourth factor "relating to others" was signi cantly correlated with the scores of the CBI, ERRI-I, and ERRI-D. The score of the fth factor "existential/spiritual change" was signi cantly correlated with the scores of the stress levels, CBI, and ERRI-D. Details are shown in Table 4.

Discussion
This study tested the factor structure, validity, and reliability of the PTGI-X-SF-J using 10 items. The results demonstrated that the PTGI-X-SF-J had a ve-factor structure similar to that of the PTGI-X and the original version of the PTGI-SF, and its model showed a good t to the data. In addition, this study con rmed the moderate to good validity and reliability of the PTGI-X-SF-J using the scores of the stress levels, CBI, and ERRI and Cronbach's alphas.
Although the factor structure of the PTGI-X-SF-J was the same as that of the original version of the PTGI-SF, the items constructed for the factors of the PTGI-X-SF-J, especially items concerning existential/spiritual change, were different from those of the original version of the PTGI-SF. That is, items for the "existential/spiritual change" factor in the PTGI-X-SF-J were "I feel more connected with all of existence" and "I have a greater sense of harmony with the world," while items concerning "spiritual change" factor in the original PTGI-SF were "I have a strong religious faith" and "I have a better understanding of spiritual matters." The newly selected two items of the PTGI-X-SF-J were the same items evaluated as highly endorsed by Japanese participants in a previous study [25]. The current results re ect more diverse perspectives and better capture the broader domain of existential and spiritual personal growth, instead of narrowly focusing on religiosity. The majority of Japanese people do not believe in a speci c religion or in God. Indeed, 68.7% of the participants in the rst study (408 Japanese university students) answered that they did not believe in a speci c religion. In addition, a previous study showed that only 30% of the Japanese population have a speci c religious faith, and this percentage is the lowest among developed countries [35]. Although the majority of Japanese people do not believe in a speci c religion or a higher power, they are likely to have a unique sense of spirituality and traditional spiritual behaviors in daily life [36]. For example, there are traditional spiritual events called "Omiyamairi" and "Shichigosan" for which parents take their children to a local shrine to pray for their children's good health and development when the children are one month or three, ve, and seven years old because they believe a local god or "Kami" protects them and their family. Other examples include an annual event called "Hatsumoude" for which Japanese people go to a local shrine or any shrine depending on what they want to pray for on the rst few days of a new year and a local custom called "Obon" for which Japanese people pray and welcome their ancestors during the four days of August because they believe their ancestors return to this world. Although Japanese people are not likely to strongly believe in a speci c region, they believe in different kinds of gods and spiritual existence, including local and other gods living in a shrine, ancestors, animal gods or spirits, and gods or spirits existing in a mountain, river, owers, and sea; further, they believe in living together and being protected by the above-mentioned gods and spirits [36]. This suggests that when Japanese people experience psychological struggle due to a stressful life event that they experienced and its impact on their lives, they may feel reconnected with "Kami" or gods and spiritual existence around them through exploring the meaning of their struggle for life and development and praying to many "Kamis" or gods or any kind of spiritual existence they believe in or just feel. These culturally unique spiritual experiences were; however, not well captured by the original items such as "having a stronger religious faith" but reasonably well captured by the items we selected based on the PTGI-X-J in the current samples, such as "more connected with all of existence." Regarding the validity of the PTGI-X-SF-J, the correlations between the total and subscale scores of the PTGI-X-SF-J and the scores of the CBI and ERRI-D were consistent with the results of previous studies.
Previous studies indicated that persons with higher PTG are more likely to reconsider what they used to believe in [32,37,38,39] and think deeply, deliberately, and constructively about the meaning of their stressful events [32,38,39]. Only two subscales of the PTGI-X-SF-J were shown to be correlated with the ERRI-I. Taku and her colleagues [32] have indicated that during a certain period after a stressful event, people are more likely to experience higher levels of intrusive ruminations (i.e., thinking unconsciously and repeatedly about stressful events) than deliberate ruminations, and this would in uence their PTG. Due to the cross-sectional design of this study and the characteristics of the participants (e.g., university students with relatively younger age), the range of duration after a stressful event might be wider than that captured in the present study. Therefore, a clear correlation between the PTGI-X-SF-J and ERRI-I was not reported in this study.
In addition, there was no correlation between the PTGI-X-SF-J and PCL-5. The results did not support the ndings of a previous study among Japanese undergraduate students [22] but were overall consistent with studies showing negligible to small positive correlations. Butler et al. (2005) and Zebrack et al. (2015) suggested that the relationship between trauma symptomatology and PTG is not linear and that it has an inverted U-shaped relationship [40,41]. This means that fewer PTSD symptoms are positively correlated with PTG, and more PTSD symptoms are negatively correlated with PTG. The scores of the PCL-5 in this study varied widely, which might have directly led to no linear correlations between the variables in this study. Thus, this result should be cautiously interpreted, and further studies are necessary.

Clinical implications
Developing the PTGI-X-SF-J using only 10 items could contribute to assessing PTG among Japanese people more e ciently by minimizing their burdens, as this would decrease the total time spent to complete the questionnaire. The PTGI-X-SF-J should be more useful when assessing PTG among people with severe physical or psychological distress due to serious, stressful events, such as illnesses (e.g., cancer), accidents, natural disasters, and other life-threatening events to prevent their further burdens when responding to scales. In addition, the PTGI-X-SF-J was developed using items that were more suitable for the broader spirituality of Japanese people. This will lead to a more accurate assessment and understanding of PTG among the Japanese and provide an effective intervention that respects their spirituality and existential experiences, thereby fostering their PTG. Finally, because the PTGI-X-SF-J was developed using the same factor structure ( ve factors) and the same number of items (i.e., 10 items) as the original version of the PTGI-SF developed in the U.S., this scale can be compared with scales in previous and future studies in other countries. Moreover, it will contribute to understanding the impact of culture on PTG and its mechanism and developing universal and culture-speci c interventions to foster PTG experiences.

Limitations
This study has some limitations. First, the participants of this study were not representative of the general Japanese population; the participants were young university students, most of whom were healthy. Thus, the results of this study should be cautiously interpreted, and a future study should be conducted among a Japanese population with diverse age ranges, socioeconomic backgrounds, and health status to con rm if the PTGI-X-SF-J is applicable to the general Japanese population and to clarify associations between the variables tested in this study. Second, this study used data from two cross-sectional surveys; thus, the test-retest reliability of the PTGI-X-SF-J could not be evaluated. To obtain evidence for the availability of the PTGI-X-SF-J, a future longitudinal study is needed.

Conclusions
We developed a Japanese version of the PTGI-X-SF (PTGI-X-SF-J) using only 10 items to measure PTG among Japanese people and con rmed its factor structure, reliability, and validity. The results of this study suggest that the PTGI-X-SF-J developed herein should be useful for assessing PTG more e ciently and accurately as it considers the unique spiritual beliefs and norms of Japanese people and reduces their physical and psychological burdens. In addition, the PTGI-SF-X-J should contribute to not only assessing PTG in Japan but also comparing PTG between countries and developing effective and speci c interventions that are sensitive to different cultures to improve PTG in the future.

Declarations
Ethics approval and consent to participate The study was approved by the institutional review boards of the two universities, one in Japan and one in the US.

Consent for publication
Not applicable.
Availability of data and materials The datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request.

Competing interests
The authors declare that they have no competing interests.  Con rmatory factor analysis using the second sample (284 Japanese students).