Factors Associated with Post-Traumatic Growth during the COVID-19 Pandemic: A Systematic Review

The COVID-19 pandemic was an unprecedented event that further stimulated the debate on the concept of trauma. To increase knowledge about the traumatic potential of the pandemic, the main objective of this study was to identify, through a systematic literature review, the main factors associated with the adaptive outcome of post-traumatic growth caused by COVID-19. Studies were selected from the PsychInfo, Embase, and PubMed databases, and 29 articles were included at the end of the screening process. The identified factors are of different natures, including personal variables such as personality traits, coping, and cognitive strategies used to face adversity, and interpersonal variables, one of the most important of which is the level of social support. In addition, several results confirmed a relationship between post-traumatic growth and post-traumatic stress symptoms, as well as indices related to psychological well-being. Finally, the results are discussed by comparing them with those already present in the literature, as well as with some of the main explanatory models of post-traumatic growth. In this regard, some of the factors identified, such as maladaptive coping, avoidance symptoms, optimism, and low-stress tolerance, suggest the possibility that the process of post-traumatic growth may also be characterized by an illusory dimension.


Introduction
The COVID-19 pandemic was an unprecedented event that further broadened the trauma debate.Due to the simultaneity and multiplicity of stressors, its effects may represent a unique type of trauma that has not yet been represented within the main paradigms [1].The main sources of stress were economic uncertainty, fear of contagion, grief, and lockdown, which resulted in the greatest psychological distress [1].The lockdown represented a strong psychological stress factor that increased social isolation, loneliness, anxiety, boredom, insomnia, and depression [2].Many studies have focused on the negative effects of trauma caused by the pandemic [2][3][4][5][6][7][8][9][10][11][12][13].These effects concern both the direct impact on people's mental health and the indirect impact that changes in lifestyle, including increased sedentariness and reduced sleep quality [8,9], have had on well-being.
Other studies have examined the presence of positive changes that occurred in people's lives as they attempted to cope with this adverse event [14][15][16]; these positive changes can be identified with the process of post-traumatic growth (PTG).According to Tedeschi and Calhoun's model [17], post-traumatic growth is an individual's experience of significant positive change arising from the struggle with a major life crisis.These changes result from the attempt to cope with a seismic event that has resulted in the shattering of one's cognitive schemas [18].People who go through this type of traumatic experience develop beyond their previous level of adaptation or psychological functioning and therefore experience growth [17].These authors explore personality traits related to growth, emphasizing creativity in problem-solving and the ability to regulate behavior in the external environment [19].Following a challenging event, individuals undergo emotional, cognitive, and behavioral shifts, enteing a phase of rumination and adopting emotion-based coping strategies, leading to eventual growth marked by improved discomfort management, serenity, self-awareness, increased life appreciation, and enhanced creativity in behavior [19].In the 'Janus Face of Self-Perceived Growth' model [20], also based on the work of Taylor et al. [21], it is hypothesized that, in addition to this dimension of real growth, there may also be illusory growth, which can be both functional and dysfunctional in relieving the stress caused by trauma [20].
For the purposes of this study, it is important to clarify the concept of trauma in the pandemic context, and in particular its meaning within the notion of PTG, as opposed to the meaning it assumes in relation to other trauma outcomes, such as PTSD.The latter is based on a conceptualization of trauma that requires "actual or threatened death, serious injury, or sexual violence" [22].In contrast, Tedeschi et al. [23] merge the construct of PTG with a notion of trauma that focuses on the individual's subjective reaction rather than the characteristics of the event itself.Indeed, according to the authors, the traumaticity of an event would be a function of the destructuring effect it has on the individual's cognitive schemas.Therefore, when comparing these types of trauma-related outcomes, it is important to consider that they are based on trauma constructs with significant differences.
Several studies have investigated the factors associated with PTG caused by different types of traumas, such as in breast cancer patients, college students abused in childhood, and male rectal cancer patients [24][25][26].The analysis of sociodemographic factors can also help to understand how people in more vulnerable groups, ethnic minorities, and people with mental disorders or other chronic illnesses, respond to trauma in terms of adaptive mechanisms, such as post-traumatic growth [27].Prior research has highlighted that individuals from minority backgrounds tend to express higher levels of post-traumatic growth than their counterparts in majority groups [28,29].Earlier studies have demonstrated that minority groups often report more adverse effects in the context of COVID-19 when compared to majority groups [30,31].Vulnerability can also play a role in fostering positive outcomes.To put it differently, navigating the challenges of the current crisis from a standpoint of vulnerability might present an opportunity to uncover personal and environmental resources, ultimately promoting growth [23].
Regarding COVID-19 trauma, a systematic review of the literature was conducted to identify the factors associated with PTG in healthcare workers [32].This population was one of the most vulnerable during the pandemic due to their exposure to direct and indirect trauma.
To increase knowledge of the traumatic effects of COVID-19 and to examine the protective factors associated with the adaptive outcome of post-traumatic growth, this systematic literature review aimed to synthesize studies investigating the factors associated with COVID-19-induced PTG in the general population; the only subpopulation that was excluded was that of healthcare providers, as they have already been studied [32].Furthermore, given the duration of the pandemic, individuals may also have experienced stressors unrelated to the pandemic context, such as illness or the loss of a loved one.For this reason, only studies that used a measure of PTG that was able to capture the positive changes that individuals reported as directly related to the pandemic context were included in this review.
This review addresses a significant gap in the scientific literature on the impact of the COVID-19 pandemic on mental health.While other systematic reviews and metanalyses [13,33,34] have focused on summarizing the factors associated with adverse COVID-19 outcomes, such as PTSD, this review broadens the perspective by compiling the factors associated with the adaptive outcome of pandemic-induced PTG.Furthermore, investigating these factors in the wider population allows for the identification of a plethora of data that greatly aid the comprehension of the PTG process, as well as the wider effects of trauma.Understanding these data is crucial due to the complexity and diversity of factors associated with this positive outcome, which makes developing protocols for the active promotion of PTG challenging.Thus, it is imperative to undertake research to comprehend these factors and facilitate the implementation of practices that mitigate the adverse effects of trauma and encourage positive changes.

Materials and Methods
This systematic review was carried out following the PRISMA Statement.The protocol was registered on the PROSPERO database (Record ID: CRD42023398006).

Search Strategy
Searches were conducted in the following databases on 23 December 2022: PubMed, PsychInfo, and Embase.The keywords and text words used in the search for each of the considered databases were "posttraumatic growth", "positive change", "PTG" and "stress-related growth".See Supplementary Material S1 for details of the search strategy.Reference lists of included articles and previous reviews were also searched.

Eligibility Criteria
All studies that investigated any factor associated with PTG caused by COVID-19 in the general adult population (18+) were included.The PTG scale had to be validated, standardized, and adapted to the context of COVID-19.Scale adaptation required that questionnaire instructions or items were modified to capture the positive changes that individuals reported as a result of the specific context of COVID-19.Studies had to have been published in English or Italian during the pandemic period and have a cross-sectional, longitudinal, or RCT design.Studies not meeting these criteria were excluded.Studies conducted on healthcare workers were also excluded.

Study Selection
Two authors (S.B. and G.T.) independently conducted standardized assessments to determine study eligibility according to the inclusion criteria.The abstracts were first screened, and all the full texts of all potential contributions were analyzed.Any disagreement was discussed with the other two authors (S.C. and A.B.) before agreement was reached.See Supplementary Material S2 for the study selection flowchart.

Data Extraction
Data from the selected studies were inserted into a standard template.Extracted data covered the year of publication, study design, population type, nationality, sample size, data collection period, mean age, sex, PTG assessment measure, instruments used to measure the associated factors, and the main outcomes related to PTG.Where available, information on COVID-19 prevention and control measures in place at the time of data collection was also included.

Quality Assessment
To assess the methodological quality and the internal validity in terms of the risk of bias (ROB) of the included studies, the Joanna Briggs Institute (JBI) critical appraisal checklist for analytical cross-sectional study was used [35].The JBI checklist is composed of eight items regarding inclusion criteria, an adequate description of the subject and setting, appropriate measurement of exposure, criteria for measurement of the condition, the identification of confounding factors and strategies to deal with, the reliability of outcomes measures, and the appropriateness of the statistical analysis, with each item answered as "yes", "no", "unclear" or "not applicable".For classification purposes, when the total number of "yes" ranged from 0 to 2, the study was classified as having high ROB; from 3 to 5, the study was classified as having a moderate ROB; and when this number was at least 6, the study was classified as having a low ROB.Two independent researchers of the review team assessed ROB, and differences were resolved through discussion among all the authors.

Study Synthesis
The results of the evidence found are presented as a narrative synthesis.After reading and thoroughly examining the main associations reported in the included studies, several key themes were identified, which supported the organization and comparison of the results.

Results
The PRISMA flowchart describing the selection process, including reasons for exclusion, is presented in Supplementary Material S2.The initial search retrieved 866 articles after duplicate removal.Of these, only 29 articles were considered eligible for inclusion in this review.Table 1 provides an overview of the main data extracted from the studies.Of the 29 articles included, 18 were cross-sectional, 9 were longitudinal, and 2 were prospective cohort studies with cross-sectional data.All the articles included were written in English.Seventeen articles used the PTGI-21 measurement scale, eight used the PTGI-SF scale, two used the PTGI scale, one used the PTGI-13 scale, and one used the PTGI-S scale.The studies used samples from different populations, including workers, students, people with psychiatric diagnoses, veterans, people infected with COVID-19, pregnant women, and people who had experienced bereavement due to COVID-19.The factors associated with PTG examined in the studies are multiple and heterogeneous and were therefore divided into five categories: sociodemographic factors, COVID-19-related factors, individual factors, relational factors, and factors related to psychological well-being or distress.

Association between PTG and Sociodemographic Factors
A relationship between PTG and ethnicity has been found in several studies [39,44,54,58].In particular, Asians were less likely to report PTG [44], whereas in a sample of Arab and Jewish women living in Israel, Arab women experienced higher levels of growth [39].Finally, Caucasian/European Americans reported lower levels of growth [58].In contrast, another study measured higher levels of PTG in the non-white ethnic group [54].Also, in Northfield and Johnston's study [55], although ethnicity was not a significant predictor of PTG, a group difference was evident between African American and Caucasian participants, with African American participants reporting higher levels.Considering age and sex/gender, no significant differences in relation to PTG were reported in some studies investigating these variables [37,40,46,49,50,59,62,63]. In contrast, in the study by Celdrán et al. [38] and Fino et al. [42], women reported higher levels of growth, but of all the sociodemographic variables considered in the study by Celdrán et al. [38], only younger age significantly correlated with higher PTG, and the same was found in the study by Northfield and Johnston [55]; by contrast, in the study by Na et al. [54], being female was associated with pandemic growth.In the study by Ikizer et al. [46], only the level of education was a predictor of PTG, as higher levels of education were associated with lower levels of PTG, while being younger was only associated with negative outputs, such as higher levels of pandemic-related stress.In contrast, in the study by Lau et al. [50], having a university degree was associated with higher odds of PTG, as was having a higher monthly household income than the sample mean.In the longitudinal study by Landi et al. [48], being older was negatively correlated with PTG.In the study by Yan et al. [64], of all sociodemographic variables, only patients grouped based on their place of residence had a significant difference in PTG, i.e., those living in non-urban areas had higher levels than participants living in urban areas.Finally, in the study by Xiao et al. [61], having children was significantly associated with PTG, and in particular in the study by Chasson et al. [39], being primiparous was associated with higher PTG.

Association between PTG and COVID-19-Related Factors
In the study conducted by Celdrán et al. [38] and Hyun et al. [44], PTG showed a significant association with COVID-19 experience.However, only individuals who were infected with COVID-19 demonstrated significantly higher scores on the PTGI-SF.Anxieties and worries related to COVID-19 were associated with higher PTG [39,44], as was fear of contracting COVID-19 [53].Similarly, in the study by Na et al. [54], most of the variance in pandemic-related PTG was explained by concerns about the effect of the pandemic on one's physical and mental health.In the study by Fino et al. [42], fear of COVID-19 was associated with both positive mental health outcomes (post-traumatic growth) and negative outcomes (depression and anxiety), and these relationships were mediated by the type of coping strategy used.In the longitudinal study by Landi et al. [48], COVID-19 infection during the study period was positively associated with PTG at time 2 (9-19 October 2020) but not at Time 1 (9-19 July 2020).In the study by Lewis et al. [51], higher PTGI-SF scores were strongly associated with the perception of the pandemic as traumatic.Specifically, being with a family member or close friend who experienced quarantine or who tested positive for COVID-19 was correlated with a higher likelihood of PTG [50].In the study by Xiao et al. [61] involving adult patients cured of COVID-19 and discharged from the hospital between 1 February and 30 April 2020, significant protective factors of PTG included the clinical classification of COVID-19 infection at hospital admission.Consistent with this result, in Yan et al.'s study [64], the time from onset to diagnosis was negatively correlated with PTG, indicating that shortening this process could help improve patients' PTG.Finally, a study examined the relationship between prolonged grief (PG), post-traumatic stress (PTS), and PTG in individuals who have suffered bereavement due to COVID-19 [40].The results showed that when the deceased was older, individuals were more likely to report high levels of PTS and PG.In contrast, conflicts in the relationship with the deceased person led to a lower likelihood of being in the group with high levels of growth and low levels of PTS and PG.At the same time, the loss of a younger loved one and the presence of a close relationship with the deceased increased the likelihood of experiencing moderate or high levels in all three dimensions.

Association between PTG and Individual Factors
Regarding the association between PTG and individual characteristics, several studies have revealed a significant association with the process of deliberate rumination [36,46,58,59].A relationship was also found between the employment of cognitive reappraisal and cognitive flexibility with PTG [48,49,52].Specifically, the connection between PTG and cognitive flexibility was solely detected in those who have reported high levels of post-traumatic stress [48]; cognitive reappraisal, coupled with social support, mediated the relationship between agency thinking and PTG [49]; and cognitive reappraisal, together with positive coping, mediated the relationship between psychological resilience and PTG [52].In this regard, another study has also confirmed the relationship between resilience and growth [44].Another important individual characteristic that interacts with PTG is the type of coping strategy used.In the study by Kalaitzaki et al. [47], during the first lockdown in Greece, PTG was associated with both adaptive coping strategies, i.e., positive reframing, religious coping, and the use of emotional support, and maladaptive coping strategies, i.e., self-blame, denial, and substance use; in contrast, during the second lockdown, this association was observed only with adaptive coping strategies.In contrast, in Fino et al.'s study [42], the use of a positive coping strategy (engagement coping) positively mediated the effect of fear of COVID-19 on PTG, whereas negative coping (disengagement coping) mediated the effect of fear of COVID-19 on anxiety and depression.Also, in the study by Yan et al. [64], the use of positive coping strategies was associated with higher PTG levels.Finally, in the study by Xie and Kim [62], a correlation was found between PTG and problem-focused coping, emotion-focused coping, and social-support coping while avoidance coping mediated the relationship between conscientiousness, agreeableness, and PTG.Regarding other personality traits, the study by Casali et al. [37] revealed that out of the six character-related virtues (wisdom and knowledge, courage, humanity justice, temperance, and transcendence), only humanity was significantly associated with PTG.Optimism and self-compassion [39], self-transcendence [63], agreeableness [54,62], selfesteem [64], and sense of coherence [50] were also associated with higher levels of PTG.Other personality traits associated with PTG were extraversion, conscientiousness, and emotional stability [62].Protective psychosocial characteristics associated with PTG included religiosity/spirituality, purpose in life, and PTG compared to previous trauma [54].The study by Shigemoto et al. [58] also revealed that those who identified as religious tended to experience higher levels of PTG.Wang and Huang's study [60] showed that PTG significantly and positively influenced university students' entrepreneurial intention and that self-efficacy and prosocial tendencies mediated this relationship.In the study by Xie et al. [63], the results showed that COVID-19-related PTG was a positive factor in university students' life satisfaction and that personal values played a mediating role in this relationship.Among the predictors of PTG, the centrality of the event was found to be a significant factor [59]. Regarding the variables most related to the pandemic, the study by Xiao et al. [61], conducted among patients hospitalized for COVID-19, revealed an association between self-stigmatization and PTG.Finally, intolerance of uncertainty was associated with higher levels of PTG only in Jewish women (but not in Arab women) and in women with higher levels of self-compassion [39], whereas tolerance of distress was associated with lower levels of PTG [44].

Association between PTG and Relational Factors
With regard to interpersonal variables, in the studies by Wall et al. [59] and Xiao et al. [61], social support was found to be a significant protective factor for the development of PTG.The role of social support in the ability to cope with trauma and bring about positive change was also confirmed in a sample of people discharged from the hospital after hospitalization for COVID-19 [64].In Kalaitzaki et al.'s study [47], perceived emotional social support during the first lockdown and perceived instrumental social support during the second lockdown were predictive of growth during both lockdowns.However, the results of Celdrán et al. [38] showed that a state of increased contact with others was not necessarily associated with PTG.In fact, both increased and decreased perceived loneliness were significantly associated with PTG.In addition, the authors found that an increase in meaningful conversations was associated with growth.In the study by Northfield and Johnston [55], only social support from family or friends was associated with PTG, whereas this relationship was not observed for other significant others.Hyun et al. [44] also found a positive association between PTG and family connectedness.In the study by Matos et al. [53], social connectedness, in terms of compassion and perceptions of social safety, predicted higher levels of PTG.The impact of the social dimension is manifested not only in the level of support received but also in how socially active one feels; indeed, an association was found between social engagement before and during the pandemic and perceptions of growth [49].Interpersonal trust, i.e., rating others as trustworthy, was also associated with all dimensions of PTG [41].Only one of the included studies focused on the relationship between work context and PTG [57].The results showed that perceptions of the psychosocial safety climate had a positive and direct effect on PTG.Finally, at the macro-social level, the "social" dimension of growth (i.e., relating to others) fully mediated the national identity-interpersonal trust association [41].

Association between PTG and Factors Related to Psychological Well-Being and/or Distress
Regarding the relationship between PTG and mental health outcomes, the study by Hyun et al. [44] showed that PTSD symptoms were significant predictors of higher PTG levels; the study by Na et al. [54] revealed that pandemic-related PTSD avoidance symptoms explained a significant proportion of the variance in pandemic-related PTG; and the study by Yan et al. [64] revealed a positive correlation between PTG and PTSD in discharged COVID-19 patients, and patients with high PTSD exposure had higher PTG.In general, several studies have confirmed an association between post-traumatic stress symptoms (PTSS) and PTG experienced during the pandemic [36,[46][47][48]; in addition, the study by Ikizer et al. [46] revealed an association between post-traumatic depreciation and PTG.The relationship between PTSS and PTG also appears to be influenced by other factors.Northfield and Johnston [55] found a strong positive relationship between psychological distress and growth that was mediated by social support, such that the relationship was stronger at higher levels of social support.Lau et al. [50] found that PTG was more likely in participants with high levels of post-traumatic stress but also a high sense of coherence.The results of the study by Chen and Tang [40] identified four profiles of prolonged grief, post-traumatic stress, and post-traumatic growth in people who had suffered bereavement due to COVID-19; two of these profiles were characterized by moderate and high levels of both PTG and PTS.The study by Pietrzak et al. [56] showed that the prevalence of PTG was higher in veterans with PTSD symptoms and that positive changes in appreciation of life and social relationships (two dimensions of PTG) related to the pandemic were associated with a significant reduction in the likelihood of suicidal ideation.In the study by Lewis et al. [51], higher scores on the PTGI were associated with higher levels of psychological well-being, and in the subsample of participants who perceived the pandemic as traumatic, PTG was associated with higher PTSD scores.Casali et al. [37] also confirmed the role of PTG in mental health, as it mediated the relationship between positive personality traits and psychological well-being.Furthermore, depressive symptoms were predictors of lower levels of PTG in the study by Hyun et al. [44], whereas in the study by Hyun et al. [45], it was observed that at low levels of pandemic-related stress, depressive symptoms were similar for young adults with low, moderate, or high levels of PTG.However, at high levels of pandemic-related stress, young adults with low PTG had the highest levels of depressive symptoms, whereas those with high PTG had the lowest levels of depressive symptoms.In addition, PTG appeared to play a protective role against depressive symptoms, as it attenuated the effect of COVID-19-related stress in 2020 on depressive symptoms in 2021.Finally, in the study by Goutaudier et al. [43], the highest levels of PTG were found in participants who reported moderate levels of anger, fear, and happiness during the first lockdown, whereas in the study by Yan et al. [64], a negative association was observed between PTG and anger.

Quality Assessment of the Included Studies
Notably, 3 studies (10.34%) had a low ROB, while 26 studies (89.65%) had a moderate ROB.None of the studies demonstrated a high ROB.Regarding study participants' recruitment and sampling procedures, 12 studies (41.37%) did not report enough information.Three studies (10.34%) did not appropriately describe the study subjects and research setting.In all studies, adequate data analyses were carried out.Details about the results concerning the ROB assessment of the included studies are summarized in Table 2.

Discussion
To the best of our knowledge, this is the first systematic literature review that has synthesized studies investigating the factors associated with PTG induced by COVID-19.Among the sociodemographic variables, the synthesis of the studies showed already known associations, including those with young age [65] and ethnic minority status [28,29].With regard to age, the fact that being younger is associated with higher levels of growth is also consistent with the model proposed by Tedeschi and Calhoun [18], according to which young people may be more open than older people to the learning and change that enables the growth process.Notably, one study found that the Asian American population was less likely to develop PTG than the American population [44].This finding can be interpreted in the specific context of COVID-19, where people of Asian origin have experienced stigma and discrimination, which may have affected their mental health and ability to seek help [66], and consequently, their ability to experience positive change.The synthesis of studies on the association between PTG and income and education levels showed contradictory results.Ikizer et al. [46] found that PTG was linked to lower educational attainment and anticipation of financial risk, and higher education to lower levels of PTG, PTS, and PTD.By contrast, Lau et al. [50] found that PTG was linked to tertiary education and higher economic income, and on this basis, they suggest that education and higher income may serve as practical coping resources, in addition to psychological ones, and may mediate the relationship between stress and PTG.These disparities may be clarified by Tedeschi and Calhoun's model [18].If the process of PTG necessitates a "seismic" event that impacts individuals' lives, leading to the questioning of significant mental patterns, it may be hypothesized that, while higher education and its work-related implications may have corresponded to reduced stress and mitigated the effect of the pandemic on mental health during COVID-19, the level of education was not always a protective factor due to the numerous stressors caused by the pandemic.In this regard, one of the factors associated with PTG is the centrality of the event, i.e., how critical a particular event is to a person's identity and life story; the greater the centrality, the greater the level of growth [59].Considering the interplay of these sociodemographic variables, it is crucial to highlight that numerous factors need to be considered to comprehend the varied reactions toward extremely demanding circumstances, such as the pandemic context.
Another interesting finding in the context of the pandemic is the association between PTG and increased loneliness [38].Despite many studies confirming the importance of social support in supporting the growth process, as discussed by the authors, this finding opens the possibility that a change in the relational dimension, whether in terms of increased or decreased loneliness, could stimulate growth.Such a change could challenge one's schemas and support the growth process.
In addition to the social dimension, many individual factors have been associated with PTG.Understanding these factors has important clinical implications for trauma interventions.This knowledge enables the advancement of strategies and procedures aimed at fostering PTG within the therapeutic alliance, a factor that research has demonstrated to be closely linked to psychological well-being.In this regard, the study by Pietrzak et al. [56] revealed that although the prevalence of PTG was higher in veterans with PTSD symptoms, positive changes in life evaluation and social relationships related to the pandemic were associated with a significant reduction in the likelihood of suicidal ideation.The association with PTSS and psychological distress is consistent with the possibility that the process of PTG requires a significant threat or the shattering of fundamental schemas, often accompanied by significant psychological distress [18].Indeed, the association observed across multiple studies between PTG and concerns related to COVID-19 underscores the traumatic impact of the pandemic and the unsettling influence it exerted on individuals' mental well-being.Furthermore, the context of COVID-19 has accentuated the range of reactions to trauma, including those that may initially seem contradictory to one another.Indeed, the study by Ikizer et al. [46] showed an association between PTG and post-traumatic depreciation.Existing literature data indicate that this aspect may manifest separately from PTG and within the same domains [67,68].Such an association in the pandemic context suggests that the complexity of trauma may lead to both positive and negative changes in the same dimensions, which are related to each other.Nevertheless, more data are needed to clarify the relationships between these forms of trauma.
Furthermore, as a speculative hypothesis, we suggest that some factors emerging from the synthesis of the studies indicate the potential presence of an illusory dimension within PTG, consistent with the concept of the "Janus Face of Self-Perceived Growth" [20].In particular, the literature underlines a positive association between PTG and maladaptive coping, avoidance symptoms, avoidant coping, and optimism traits, and a negative association with distress tolerance.Although these factors may represent initial attempts to alleviate the stress caused by a sudden event without negative consequences, the association with avoidance symptoms and coping may have negative effects on individual adjustment [20].
Finally, it is important to consider that few studies have reported clear data on the prevalence of PTG, which complicates the interpretation of the results.A comparison of the studies that have reported these data reveals that the prevalence of this phenomenon does not seem to be uniform across the samples studied.
This systematic literature review has several limitations that need to be considered when evaluating the results.Firstly, all studies used a self-report scale to measure PTG; therefore, there is a risk that participants may have under-or overestimated the information.At the same time, some studies used non-standardized measures for the associated factors, which are less sensitive in capturing the phenomenon of interest and hinder an accurate comparison of the factors related to PTG, as well as a clear understanding of the variables associated with the growth process.Therefore, there is a need to use more standardized measurement tools that can effectively capture the desired outcome.Secondly, the data collection process required participants to complete the PTG questionnaire with a focus on positive changes because of the pandemic.Although this criterion allowed for a better understanding of the specific effects of COVID-19, participants may have found it difficult to distinguish between specific changes caused by the pandemic and other positive developments in their lives not related to the pandemic.In addition, it is important to consider the limitations of the cross-sectional nature of most of the selected studies, including the difficulty of interpreting the associations identified and the inability to examine the temporal relationship between outcomes and other factors [69].Finally, although all included studies were conducted during the pandemic, there were periods of heightened crisis due to increased contagion and restrictions, alternating with periods of lower tension.This may make it difficult to compare and interpret results, especially when considering PTG as a process and therefore sensitive to trauma exposure times.In this respect, most studies did not use time-sensitive measures of adverse experiences related to COVID-19.The limitations highlighted in this review underscore the importance of adopting an end-to-end research approach, emphasizing the need for a meticulous consideration of measurement tools, data collection methods, and the temporal dynamics of trauma exposure to ensure more standardized and robust analyses in future investigations of post-traumatic growth associated with the COVID-19 pandemic.

Conclusions
This systematic literature review provides important data for understanding the effects of the COVID-19 pandemic and, more generally, the effects of trauma and their association with PTG.This review suggests important future research directions for understanding the phenomenon of PTG.It is fundamental to investigate whether the currently available measures can detect real rather than illusory growth, and how different forms of response to trauma interact with each other.Finally, the synthesis of the studies showed a wide heterogeneity of protective factors that should be considered when implementing interventions to support people with traumatic experiences.

Table 1 .
Overview of the main data extracted from the studies.
Pandemic-related distress measure consisted of 14 items capturing four areas of distress: financial stress, COVID-19 health risk, COVID-19-related worries, COVID-19-related grief; Patient Health Questionnaire (PHQ-8); seven-item Generalized Anxiety Disorder Scale (GAD-7)At low levels of pandemic-related distress, depressive symptoms were similar for young adults with low, moderate, or high PTG; at high levels of pandemic-related distress, young adults with low PTG had the highest levels of depressive symptoms, and young adults with high PTG had the lowest levels of depressive symptoms; PTG at T2 buffered the effect of COVID-19-related distress from 2020 on depressive symptoms in 2021 among US young adults.

Table 2 .
Risk of bias (ROB) assessment of the included studies.