Stress-related growth (SRG), a type of personal growth after stressful life events, mainly manifests through enhanced social and personal resources and developed or changed coping skills [9]. Previous studies observed that coping flexibility is associated with enhanced performance under stress [10]. Coping flexibility refers to the ability to discontinue ineffective coping strategies and generate and implement alternative coping strategies [11], which could help individuals shift their perspectives and ways of thinking, generate new strategies, and cope better with stress. SRG occurs when individuals extract meaning from the potential negative effects of stressful events. This process requires both the ability to switch cognitive subsets and the ability to evaluate and switch strategies in coping. Therefore, for SRG to occur and for one’s perceptions toward stressful events to change, mindset and strategy shifts become critical [12]. Individuals with high coping flexibility were more likely to change their schemas in a positive direction, compared with those with low coping flexibility [9]. Further, individuals with high coping flexibility make greater use of adaptive coping strategies in stressful situations, with the utilization of multiple adaptive coping strategies being associated with better resilience and fewer mental health problems [10, 11]. Thus, coping flexibility has been used as an indicator of SRG.

The cyclical model of stress resilience and SRG assumes that meaning-making is an effective strategy to facilitate an individual’s ability to create positive outcomes [9]. Meaning-making refers to an individual’s adaptive function under stress and the process by which they reconcile their beliefs and goals to cope with stressful situations, thus changing the way they assess a situation [6, 12]. The meaning-making model suggests that individuals possess both global and situational meanings; when individuals are faced with negative stressful situations, these global and situational meanings can conflict with each other and cause distress. Thereafter, individuals spontaneously generate meaning-making processes that result in outcomes such as the individual’s perceived SRG and positive changes. For this process, negative stressful situations are a prerequisite, and differences in situational and global meanings are the driving force behind individuals’ meaning-making [12].

The meaning-searching process can be exemplified through the process of accumulating individual autobiographical memories throughout one’s life course, with individuals integrating temporal information to construct meaning to guide their future lives [12]. This process involves some narrative components that are used by individuals to find common threads in past, present, and future experiences. These common threads enable them to create a coherent cognitive representation that triggers SRG and predicts higher psychological well-being [12]. Both nostalgia and thinking about the future trigger meaning-making processes that enhance self-reported sense of meaning in life and positive emotions [13, 14]. Moreover, mental simulation allows for individuals to leave the “here and now” through self-alienation—a process that integrates temporal information and the gain of causal apprehension, serving as a stable paradigm for triggering meaning-making [15,16,17]. A recent study on mental simulations found that imagining two separate events that take place in the future can initiate meaning-making processes and result in more making in life. However, imagining two separate events in the present does not; therefore, in this study, a comparison of future and present mental simulations was used to characterize meaning-making [17].

The cyclical model of stress resilience and SRG suggests that coping strategies, such as meaning-making, can act as mediators that lead to SRG: namely, meaning-making can mediate the relationship between stress and SRG. The meaning-making model also proposes that negative stressful events provide the premise for meaning-making and facilitate meaning-making in response to stress, which triggers SRG [9].

The meaning-making model suggests that negative stressful events trigger meaning-making and SRG [12]. Research in the field of psychological growth has typically conducted between-group comparisons regarding the mental health of individuals experiencing low, moderate, and high levels of stressful events. Findings suggest that very low levels of stress result in little growth compared with moderate levels of stress [18]; further, the presence of post-traumatic growth suggests that individuals experiencing high levels of stress also show growth [19]. However, these findings coincide with researchers’ beliefs that negative stressful events lead to the destruction of our basic beliefs, to the reconstruction of coping and core beliefs, and to the generation of SRG [12]; that is, they exclude the role of positive life stress, leading to a negativity bias in the field of psychological growth.

In recent times, however, researchers have started to focus on the role of positive stressors in promoting growth [20]. In fact, a meta-analysis of prospective studies showed that both negative and positive stressful events were followed by positive trends in the subdomains of self-esteem, positive relationships, and personal growth [21]. Researchers have hypothesized that any unusual event, regardless of its valence, can change core beliefs, and that positive experiences also trigger meaning construction and can act as catalysts for growth [22].

Despite the evidence on meaning-making promoting SRG, no research has explored the cognitive neural mechanisms underlying this process [12]. In the affective neuroscience model of boosting resilience, three effective pathways exist for maintaining stress resilience during stressful situations: increasing positivity, decreasing negativity, and transcending the self. These correspond to three distinct brain circuits: the reward network, amygdala, and DMN, respectively [23]. Meaning-making is an important coping strategy for transcending the self, and the latter is represented by DMN activity. Specifically, by reducing the activation of the DMN associated with self-reflection and rumination or by meaning-making, individuals can have experiences that promote self-transcendence; such promotion helps them reflect on long-term meaning-making related to stress, thus facilitating SRG [24, 25].

The DMN network is the most important subnetwork, being characterized by reduced activity in active attention-demanding tasks. Specifically, it comprises the medial prefrontal cortex (mPFC), posterior cingulate cortex (PCC), precuneus, inferior parietal lobe, hippocampus, inferior temporal cortex, and several other brain regions [15]. The DMN function is involved in attention to external and internal stimuli and in self-referential and reflective activities [26].

Early stressful life events are associated with connectivity patterns within the DMN during rest in early adulthood. Exposure to life stress during infancy might have long-lasting influences on functional brain connectivity that persist until early adulthood [27]. Therefore, the DMN plays an important role in the regulation of mental health under stress. Longitudinal fMRI studies in adolescents have found that subclinical depression and post-traumatic symptoms alter the trajectory of DMN connections, which may indicate that the network is a clinically considerable link in mental health disorders [28]. The dynamic model of thought-roaming suggests that overactivity of the DMN (including the mPFC and PCC) in the default network core leads to automatic constraints on thought increase; this leads to rumination and obsessive thinking, which are characteristic of mood and anxiety disorders [25]. Concurrently, DMN hyperactivity is associated with psychiatric disorders, such as depression and schizophrenia [29]. When engaging in self-reference thinking, individuals who meditate frequently show greater deactivation of the mPFC and PCC than individuals in the control group [30]. Thus, being able to reduce DMN hyperactivity and disengage from rumination may contribute to one’s stress resilience [23, 30, 31].

The literature also shows that an abnormal functional connectivity (FC) of the DMN contributes to stress-related disorders. For example, resting-state studies with patients with depression showed elevated intrinsic connectivity of the DMN [32], and meta-analyses have shown an association between depression and enhanced intrinsic positive connectivity, as well as between the first and diminished negative connectivity, of the DMN [33].

Despite these pieces of evidence, the reality is that findings remain inconsistent regarding the relationship between DMN connectivity and mental health. For example, in a large sample of resting-state studies, patients with depression showed reduced DMN FC compared with healthy controls [34]. This contrasts with the results of the previously cited research.

However, the evidence primarily related to the relationship between the DMN and stress-related disorders. Regarding meaning-making, only one study has linked it to the DMN [17]; in this study, enhanced connectivity of the medial temporal network, which is a subnetwork of the DMN, was associated with a self-reported meaning in life on a resting-state MRI. In other words, the study provides support for the regulatory role of DMN in meaning-making [17].

Stress is generally associated with maladjustment and dysfunction [1]; however, some studies have shown that stress can have positive effects and produce SRG [1, 4, 5]. The meaning-making model suggests that meaning-making is effective in helping individuals grow after stressful experiences [12, 19]. The affective neuroscience model of boosting resilience indicates that meaning-making is a strategy, mediated through the DMN, to transcend self to acquire coping skills and achieve SRG [23].

Despite the invaluable contributions of existing research, the studies have some limitations: first, they have mostly focused on meaning-making from negative stressful events, neglecting positive ones [20, 21]. Second, although previous research has identified the role of meaning-making in stress adaptation [6, 12], few have used a laboratory context to assess how the cognitive neural mechanisms of meaning-making contribute to SRG and coping flexibility in daily life. Third, the relationships between hyperactivity in the DMN and rumination and between the first and maladaptation under stress have been validated [25]; however, only one resting-state study has demonstrated the cognitive neural mechanisms of meaning-making [15]. To date, no studies have explored the activity and FC of the DMN during meaning-making; thus, the relationship between activity and FC of the DMN and SRG requires elucidation.

Following prior research [17], we used the paradigm of mental simulation triggering meaning-making to observe DMN activity and FC during meaning-making in a task fMRI. Specifically, whole-brain activation analysis and regions of interest (ROI) analysis were used to explore the decline in DMN activity during meaning-making and its association with SRG. Psychophysiological interaction (PPI) analysis was used to explore the diminished FC within the DMN under meaning-making using the PCC core seed point of the DMN as a starting point. The PCC, as a core subregion of the DMN, was often selected as the starting point for PPI [35,36,37]. We also built mediation models to explore whether DMN activation during meaning-making can mediate the pathway from different stressful events to the SRG. The exploratory mediation model was validated to determine whether good times or bad times are conducive to personal growth.