The efficacy and mechanism of positive psychological intervention on well-being for colostomy patients: a randomized controlled trial

The positive psychology intervention (PPI) is an effective therapy designed to motivate individuals’ positive quality and power, to help them survive in an adverse situation, and to establish a high-quality personal and social life. This study aims to evaluate the efficacy and mechanism of PPI on the psychological capital, psychological distress, and life satisfaction among colostomy patients. Patients (n = 120) with permanent stomas were recruited and randomly assigned into two groups. Patients in the experimental group (n = 60) received standard care and PPI, whereas patients in the control group (n = 60) only received standard care. The psychological capital, psychological distress, and life satisfaction were measured and compared between two groups before the intervention, the immediate post-intervention, and follow-up. All 120 patients completed the study. The hope, optimism, resilience, psychological distress, and life satisfaction score of the experimental group were significantly higher than those of the control group at T1 and T2 (P < 0.05). Self-efficacy score of the experimental group had no significant difference at the two time points after the intervention than the control group (P > 0.05). Changes in hope and resilience which belong to psychological capital mediated the intervention’s efficacy on changes in PPI on life satisfaction (β = 0.265, P = 0.005; β = 0.686, P = 0.002). PPI could effectively improve psychological capital, psychological distress, and life satisfaction among patients with stomas. Besides, our findings add novel support that increased hope and resilience are the active ingredients that promote intervention change.


Introduction
Colorectal cancer (CRC) ranks third in worldwide cancer incidence and second in cancer-related mortality [1,2]. Permanent colostomy removes the tumor and creates a stoma on the abdominal wall to provide a new artificial pathway for waste elimination [3,4]. Despite the obvious clinical benefits of a stoma, it still impairs the patient's physical, psychological, and social functioning, leading to stomarelated problems [5]. Physical changes, such as damage of self-image, incontinence, leakage, and uncomfortable clothing, make it difficult for patients to adjust [1]. In the psychological aspect, patients are faced with multiple impacts of appearance, touch, vision, and smell associated with the stoma, causing psychological distress [6]. And in the social aspect, the relationships with family members and friends may be damaged; self-awareness seems to be challenged [7].
Yanfei Jin and Yuqing Wang had equally contributed to the work.
As a positive psychological structure, psychological wellbeing is always used to measure the overall state of life [8]. It is the personal understanding and affective values of life events, including emotional reactions to events, good judgment, and awareness of satisfaction [9]. With the deepening of research on well-being, its positive effects on health outcomes have been explored. Previous studies have shown that well-being was related to more healthy coping tendencies, better disease prognosis, improved quality of life, and healthy longevity [10][11][12]. Obviously, interventions that promote well-being to improve health outcomes and reduce the negative effects of the disease are undoubtedly an important issue.
The positive psychology intervention (PPI) is an effective therapy developed in psychology, which can promote well-being and reduce ill-being [13,14]. Building and Broaden Theory provides useful insights into how positive effects broaden the scope of cognition, action, and build the individual's psychosocial resources [15]. In this theoretical framework, the "building" function facilitates the rebuilding of personal resources (including concepts such as mastery, hope, and purpose in life) that are depleted due to stress. The increase in resources, in turn, promotes an increase in positive well-being [16]. It emphasized that repeated experiences of positive emotions and strengths could reconstruct intellectual, social, and personal resources and provided an explanatory framework for the positive effects of positive activities in daily life. Compared with other therapies (e.g., cognitive behavioral therapy, interpersonal therapy, and problem-solving therapy) for dealing with mental health issues, PPI focuses less on psychological defects and more on identifying and establishing on positives (e.g., positive experiences, factors, and scenarios). Besides, such intervention is less complex and applicable in a shorter time range, which has attracted much attention in recent years [17,18]. Currently, PPI has developed specific intervention procedures and sessions, including eight empirically validated cognitive and behavioral skills, such as noticing positive events in daily life, gratitude, and mindfulness. It has been successfully applied to the general populations and clinical patients and has shown its effect on improving mental health status and well-being [19][20][21][22]. Although evidence-based PPI that can improve positive aspects has been developed and widely disseminated, it has not been used among patients with a permanent stoma in China and many other countries.
In the existing literature, in addition to the lack of examination of the effect of PPI in the context of patients with a permanent stoma, there is also insufficient research on the mechanism of PPI promoting well-being. Although numerous studies showed that PPI could promote health outcomes and well-being by improving positive states, few studies have used parallel mediation models to test the mechanism by which PPI increases well-being [23].
Several mechanisms may account for PPI effects, including changes in attentional deployment and cognitive reappraisal during the processes of emotion regulation [23]. Additionally, PPI may increase positive emotions, thoughts, and behaviors as well as psychological personal resources [24]. Psychological capital is generally defined as an individual's positive psychological development state, which is characterized by the following: (1) strive to complete challenging tasks and always keep confident (self-efficacy); (2) adhere to the goal and redirect the path to success for the goal if necessary (hope); (3) maintain a positive attitude towards the present and future success (optimism); and (4) persevere and surpass to achieve success when troubled by difficulties and adversity (resilience) [25].
According to the Build and Broaden Theory [15], positive effects facilitate the establishment of individual psychosocial resources. Psychological capital is interpreted as a positive perception of events that stimulates success based on unremitting effort and persistence [25,26]. The positive activities contained in PPI could increase psychological capital. In turn, these positive effects of psychological capital can mediate the effect of PPI on individual's well-being [25,26]. Given the PPI is a conscious and positive activity focusing on goals, which facilitates participation in thinking about a person's positive future and formulating ways to achieve goals, we believe it makes sense that increased psychological capital, including self-efficacy, hope, optimism, and resilience, mediates the effects of PPI on well-being. And these mediating variables may occur simultaneously with changes in well-being.
Therefore, the main objective of our study is to examine the efficacy of PPI on psychological capital, psychological distress, and life satisfaction among patients with permanent stoma. In addition, we considered that psychological capital is the mediating active ingredient of PPI to improve life satisfaction and reduce psychological stress; thus, our secondary objective is to explore the intervention mechanism of PPI in the process of improving well-being in the context of permanent stoma.

Design
We conducted a single-blinded, double-arm parallel, randomized controlled trial in a general hospital in northern China from 1 January 2019 to 1 January 2020. This trial was approved by the human research ethics committee of the hospital, and it was registered at Chinese Clinical Trials Registry (Registration No. ChiCTR2100052179).

Data collections
A trained research assistant collected data through face-toface questionnaire surveys with patients at the following three time points (see Fig. 1): baseline (T0), the immediate post intervention (T1, 5 weeks post baseline), and follow-up (T2, 1 month post intervention). On average, the patients filled out the questionnaires in 15-20 min.
Sample size G*Power 3.1.3 was employed to estimate the sample size. Referencing a study on the effect of PPI on the well-being of breast cancer patients [20], we took the power of 0.8 with an alpha value of 0.05, and an effect size of 0.60; considering a 30% attrition rate, approximately 120 samples were required.

Participant criteria
Inclusion criteria included the following: (1) diagnosed of CRC and had a permanent stoma with stable postoperative conditions; (2) were at least 18 years old; and (3) were willing to participate. Exclusion criteria included: (1) had a known history of, or currently had psychiatric disorders; and (2) suffered from other severe physical disorders or metastatic cancer. Dropout criteria included: (1) unable to complete the psychological intervention; and (2) loss to follow-up.

Recruitment
Participants were enrolled from the stoma outpatient and anorectal inpatient departments of a general hospital. The recruitment was carried out by trained staff who made contact with the potential participants when patients came to the outpatient or inpatient department. In both locations, the research staff introduced the research content and purpose to potential participants, screened for inclusion and exclusion criteria, and ensured that participation was voluntary.

Randomization, allocation concealment, and blinding
Participants who fully met the criteria formally participated in the trial after providing written informed consent. After the participants completed the baseline assessments, the researchers randomly assigned the participants to the experimental group and the control group according to random numbers generated by the random number generator. Allocation was made by a third party using sealed and opaque sequentially numbered envelopes. In addition, since it is impossible for psychological intervention to be completely blinding (e.g., blinding for the intervention implementers and the participants), we can only achieve single blinding, that is to say, the research data were collected and subsequently analyzed by another researcher who did not know the grouping allocation.

Intervention
The control group only received standard care, including stoma care and diet guidance, while the experimental group received both standard care and PPI (the intervention outline is shown in Supplementary Table). The specific content of our PPI was carried out in accordance with the previously published and empirically validated Moskowitz's Trail curriculum [27][28][29]. The PPI consisted of 5 sessions (once a week), each of which lasted approximately 45 to 60 min and was taught by two trained facilitators. In addition to the face-to-face intervention in the first session, participants can also choose to be taught the skills by phone or video call depending on their situation in the next 4 sessions. A detailed overview of the intervention procedures and content can be found in Moskowitz et al. (2017).

Psychological capital
The positive psychological capital was used to measure psychological capital [30]. The scale consists of 26 items that distributed in 4 factors: (1) self-efficacy; (2) hope; (3) optimism; and (4) resilience. All items were rated on a 7-point Likert scale ranging from 1 to 7 ("strongly disagree" to "strongly agree"). Based on the reliability test conducted for our study, this scale had a Cronbach's alpha of 0.941 for T0, 0.905 for T1, and 0.964 for T2.

Psychological distress
The 10-item Kessler psychological distress scale was used to measure psychological distress [31]. The scale consists of 10 items on a 5-point scale (1 = "almost none" to 5 = "all the time") with total scores ranging from 10 to 50 and higher total scores indicating higher levels of psychological distress. Based on the reliability test conducted for our study, this scale had a Cronbach's alpha of 0.819 for T0, 0.878 for T1, and 0.888 for T2.

Life satisfaction
Life satisfaction was measured with the 5-item satisfaction with life scale [32]. The scale consists of 5 items on a 7-point scale (1 = "strongly disagree" to 7 = "strongly agree") with total scores ranging from 5 to 35 and higher total scores indicating higher levels of life satisfaction. Based on the reliability test conducted for our study, this scale had a Cronbach's alpha of 0.767 for T0, 0.838 for T1, and 0.918 for T2. (1) Intervention effect analysis Chi-square test, independent sample t-test, and Mann-Whitney U tests were used to compare the variables between the two groups. The changes or differences of variables between the groups (experimental vs. control groups), within-group (time), and interaction (group*time) effects were analyzed by methods repetitive measure analysis of variance (ANOVA).

Statistical analysis
(2) Intervention mechanism analysis SEM was used to analyze of active ingredients of the intervention. The comparison of experimental group versus control group was represented by a two-valued dummy variable (scored 0 = control group, 1 = intervention group) under the two intervention conditions. We included potential mediators that significantly improved during the intervention into the model. The variables included in the final model were hope, optimism, resilience, psychological distress, and life satisfaction. All the intermediate variables and outcome variables at T1 and T2 were adjusted according to the baseline value at T0.

Patient recruitment and characteristics
The CONSORT 2010 Statement [33] was used to report this randomized controlled trial, and the CONSORT flow diagram is illustrated in Fig. 1. A total of 214 patients were enrolled in this study and assessed for eligibility, of which 120 completed the T0 assessment and were randomly allocated to the PPI and control groups. Sixty patients in both the PPI and control group completed the study and underwent post-intervention T1 and T2 assessments. Table 1 presented patients' demographic and clinical information. No significant difference existed between the two groups in the baseline data (P > 0.05), which was comparable.

Positive psychological capital
At baseline, it found no differences in self-efficacy, hope, optimism, and resilience scores between the PPI and control groups (t = 0.623, P = 0.534; t = -0.268, P = 0.789; t = 0.801, P = 0.255; t = -0.808, P = 0.140). The PPI group had significantly higher scores than that of the control group at the immediate post-intervention (t = 4.727, P < 0.001; t = 10.055, P < 0.001; t = 12.591, P < 0.001) and followup (t = 7.389, P < 0.001; t = 12.112, P < 0.001; t = 14.136, P < 0.001) in hope, optimism, and resilience. Although the self-efficacy score of the PPI group was also higher than that of the control group at the two time points after the intervention, there was no significant difference (t = 1.155, P = 0.250; t = 1.257, P = 0.211). Table 2 showed that the time factor had a significant significance, indicating that the difference in self-efficacy, hope, optimism, and resilience between the two groups at different intervention time points was statistically significant (F = 3.793, P < 0.001; F = 195.518, P < 0.001; F = 122.117, P < 0.001; F = 310.408, P < 0.001). The overall betweengroup difference was only statistically significant in hope (F = 24.650, P < 0.001), optimism (F = 99.133, P < 0.001), and resilience (F = 114.218, P < 0.001), indicating that there were still differences between patients in the two groups without considering the time factor; however, no significant between-group difference in self-efficacy was found (F = 1.513, P = 0.224), suggesting that there was no difference between patients in two groups without considering the time factor. The interaction between time and group showed statistically significant in self-efficacy, hope, optimism, and resilience, indicating that the two groups of patients had different trends change over time (F = 0.241, P = 0.004; F = 35.883, P < 0.001; F = 68.473, P < 0.001; F = 267.123, P < 0.001) ( Table 2 and Fig. 2).

Psychological distress
No difference was found in psychological distress at baseline (t = -0.251, P = 0.803) between the two groups. At the immediate post-intervention and follow-up, the psychological distress scores of the PPI group were significantly decreased than that of the control group (t = -8.391, P < 0.05; t = -9.699, P < 0.05). Both the PPI and control groups showed reductions in psychological distress over time, and there was significant within-group improvement in psychological distress (F = 356.594, P < 0.001). There was also a significant between-group difference (F = 49.779, P < 0.001) and interaction effect of group and time in psychological distress (F = 154.624, P < 0.001) ( Table 2 and Fig. 3).

Life satisfaction
There was no significant difference in life satisfaction scores between the PPI and control groups at baseline (t = 0.000, P = 0.728). The life satisfaction of the two groups after the intervention varied with the time, and the life satisfaction of the PPI group was significantly higher than that of the control group at the immediate post-intervention and followup (t = 6.810, P < 0.05; t = 14.263, P < 0.05). The ANOVA results of repeated-measures showed significant time effect (F = 55.013, P < 0.001) and interaction effect (group × time) (F = 80.503, P < 0.001). The overall between-group difference was also statistically significant (F = 108.058, P < 0.001) ( Table 2 and Fig. 3).

Active ingredients of PPI
As we did not find a significant intervention effect for selfefficacy, only hope, optimism, and resilience were included for further mediation analysis. Our data relatively fitted the structural model after appropriate modification according to modification index and empirical evidence (χ2/df = 3.792; CFI = 0.896; TLI = 0.898). Table 3 Figure. 2 The trend of self-efficacy, hope, optimism, and resilience scores before and after intervention groups Figure. 3 The trend of psychological distress and life satisfaction scores before and after intervention groups

Discussion
To our knowledge, this study is the first randomized controlled trial of PPI in people living with permanent stoma, which aims to increase psychological capital and thus affect well-being. The methodological quality of this study was high, as it met five of the six Cochrane collaboration criteria for high-quality trials [34]: (1) randomization concealment; (2) appropriate measurement of the outcome; (3) complete outcome data; (4) report of all pre-set indicators; and (5) baseline comparability of groups. The 6th criteria, blinding of participants and intervention implementers, could not be realized once they started sessions under their specified conditions. Our results showed that the PPI significantly increased the psychological capital (hope, optimism, and resilience) and life satisfaction, while also significantly reducing the psychological distress in patients with a permanent stoma. The nature of psychological capital makes it suitable for intervention that focuses on stimulating the individual positive characteristics and promoting positive growth (i.e., PPI). Its working mechanism confirms the positive and direct effect of PPI, including that positive belief could help individuals to intentionality and motivation under negative situations, positive cognition and positive emotion facilitate to maintain hope and optimism to the future, and positive personal resources to bring effort and persistence. Based on the assumption that the PPI could promote individual's positive characteristics and ability to grow their resources, our results are consistent with previous research, which confirms that interventions related to positive psychology provide the perfect conditions and environment for the development of psychological capital [35][36][37]. It should be noted that in psychological capital, although the self-efficacy score of the intervention group was increased compared with the control group, we did not find that the effect of PPI on self-efficacy is as significant as the effect of PPI on hope, optimism, and resilience. The possible reason we speculated was that selfefficacy, as an individual's belief in achieving goals, was less likely to improve in a short period of time, especially when the individual was facing major traumatic events such as cancer and permanent stoma. In addition, the sessions of PPI in this study may not be sensitive enough to the target of self-efficacy. In view of the above speculations, the intervention session specifically for strengthening self-efficacy can be added to the existing PPI, and the intervention period can be appropriately extended in future research.
The intervention mechanism analysis revealed that psychological capital was the active ingredient of change. Specifically, the increase of hope and resilience which belong to psychological capital is the active agent of PPI. This result was similar to the previous studies; that is, hope and resilience predicted the psychological status and life satisfaction among cancer patients [38][39][40][41]. It is generally believed that a high ratio of positive to negative effects is characteristic of an individual's mental health [42] and that these positive effects (e.g., positive belief, self-efficacy; positive cognition, hope; positive emotion, optimism; positive personal resource, resilience) have highly adaptive value, enabling individual to achieve a more vigorous life, a healthier lifestyle, and even a better immune system [43][44][45]. It should be noted that hope and resilience were the effective components of the intervention to promote life satisfaction at the two time points after the intervention, respectively. This may be related to the different evocations of positive effects of PPI on colostomy patients as the intervention and time continue. For example, in the initial stage of the intervention, increased hope could enable patients to think more broadly and see longer-term perspectives, while, in the follow-up stage after the intervention, increased resilience could make patients more motivated and courageous to achieve their postoperative survival goals. Overall, our results confirmed the proposed hypothesis. Patients in the intervention group showed a significant increase in well-being overtime after receiving PPI. In addition, results in our study highlighted the important role of psychological capital in well-being during cancer and enterostomy stressful events. Finally, in addition to exploring the effects of PPI on well-being, our study also addresses a gap in the literature related to the few empirical control trial studies with a longitudinal design [46], such as the efficacy of PPI in specific populations and its mechanism of action.
However, several limitations of our study must be recognized. First, due to material resources and time constraints, we only included patients from a single site so that the results may not be generalized. Thus, the effect of this intervention on other settings should be examined in future trials to compare the results. Second, the intervention implementation time and follow-up time were not sufficient; therefore, adequately powered trials with longer intervention and follow-up time are needed in the future. Third, the variables tested in this study were limited as other factors (e.g., personality traits and other psychological variables) that might further influence psychological health outcomes were not investigated. Forth, the data from this study relied entirely on patients' self-report measures, which may be biased, and therefore, the inclusion of objective health outcomes (i.e. immunological or hormonal markers) could be considered in future research to make the results more reliable. Finally, in the analysis of the intervention mechanism, the goodness of fit of the SEM only reached an acceptable critical value, which limited the generalization of the result of this study. The reason for this result may be related to the small sample size, suggesting that the sample size needs to be expanded in the future analysis of the PPI mechanism.
To conclude, our study demonstrated the clinically significant benefits of PPI such as improvement in psychological capital and life satisfaction, and reduction in psychological distress, which provide preliminary evidence for clinical practitioners to consider integrating PPI into standard care to improve well-being in patients with a permanent stoma. Moreover, our study found that psychological capital may be an active ingredient of intervention outcome; studies with larger sample size and longer intervention period are warranted to replicating the finding.