Effectiveness of Positive Psychology Interventions for Cancer Survivors: A Systematic Review and Meta-Analysis.

1
Background
Globally, the prevalence of individuals living with cancer is projected to rise by 77% by 2050, reaching an estimated 35 million cases annually [1]. Despite advancements in detection and treatment, cancer diagnosis is associated with significant psychological challenges, including post‐traumatic stress symptoms, existential distress, depression, anxiety, and reduced quality of life (QOL) [2]. Additionally, cancer treatments often result in long‐term toxicities such as fatigue, physical appearance changes, and sexual dysfunction, contributing to substantial individual and health system burdens [2, 3, 4]. It is therefore essential to address and mitigate the negative sequelae while promoting wellbeing and quality of life among survivors.
A large body of evidence has demonstrated the effectiveness of psychosocial interventions tailored to cancer survivors to address the negative impacts [5, 6, 7]. Interventions vary from gold‐standard evidence‐based cognitive behavioral therapy and acceptance and commitment therapy, to body–mind practices of mindfulness meditation, breathlessness interventions, and music therapy [5, 6, 7]. However, they have predominantly focused on managing psychological distress and psychopathology symptoms of anxiety and depression, rather than distress prevention and promotion of psychological wellbeing. This trend is evident in a recent review by Semenenko et al. [6], encompassing 25 studies, where 64% of included studies prioritized the measurement of psychological distress or psychopathology outcomes. Similarly, a recent review of 13 studies on psychosocial interventions for ovarian cancer revealed that 92% of outcomes focused on psychological distress, while outcomes related to social wellbeing, psychological wellbeing and cancer‐specific concerns, such as fear of cancer recurrence and sexual dysfunction, were scarcely addressed [7]. This emphasis on distress‐based outcomes, while important, may result in the underrepresentation of other crucial aspects of a cancer survivor's overall mental wellbeing.
Traditionally, mental wellbeing has been operationalized based on the presence or absence of clinically relevant symptoms of psychopathology or psychological distress [8]. However, Keyes [9] proposed a dual‐continua model, conceptualizing mental wellbeing as comprising two interrelated dimensions: (1) the absence or presence of mental illness, ranging from severe psychological disorders to no mental health conditions; and (2) the level of psychological wellbeing, spanning from languishing (low wellbeing) to flourishing (high wellbeing). This model, recently validated by Stephens et al. [10], highlights that the absence of mental illness alone does not equate to positive wellbeing. Instead, mental wellbeing combines both the absence of distress with desirable psychological states, such as positive affect, purpose, and supportive relationships [10, 11]. Constructs such as psychological wellbeing, meaning in life, post‐traumatic growth, self‐compassion, and flourishing were identified as key determinants of successful cancer adjustment [12, 13, 14]. These constructs align with the principles of positive psychology [11], which aims to enhance human flourishing and supports the need for a more holistic approach that incorporates both the reduction of psychological distress and the promotion of wellbeing.
Positive psychology focuses on the science of human flourishing, promoting psychological, social, and emotional wellbeing [9, 11, 15]. This approach has been shown to positively influence health outcomes, including biological processes such as neuroendocrine and immune function, which may be directly related to disease progression and symptom management [16, 17]. One influential perspective on positive psychology is Seligman's (2008) [11] PERMA model, which identifies five key components of wellbeing: Positive Emotion, Engagement, Relationships, Meaning, and Accomplishment. Together, these elements foster flourishing rather than merely alleviating distress, offering a holistic approach to mental health. The model suggests that enhancing these aspects not only increases life satisfaction but can also support resilience, improve recovery trajectories, and foster treatment adherence in individuals facing health challenges, including cancer patients [11, 18, 19].
In recent years, several reviews have explored the effectiveness of positive psychology interventions (PPIs) for cancer survivors, with notable contributions by Casellas‐Grau et al. [12], Otto et al. [20], and Tian et al. [21]. Casellas‐Grau et al. [12] focused exclusively on breast cancer patients, while the other reviews included individuals with various cancer types. While these reviews highlight promising outcomes in enhancing wellbeing, resilience, and self‐efficacy, they also underscore key limitations. A lack of consistent definitions and theoretical grounding for PPIs complicates comparisons and generalizability across studies. For instance, interventions included in these reviews, such as mindfulness‐based stress reduction (MBSR), acceptance and commitment therapy (ACT), and spirituality‐based approaches, are rooted in philosophies and frameworks outside traditional positive psychology principles, such as PERMA [11]. This definitional variability limits clarity in distinguishing PPIs from other therapeutic modalities [22]. Methodological variability, including the exclusive reliance on randomized controlled trials (RCTs), further narrows the scope, potentially excluding valuable insights from alternative study designs and introducing publication bias by favoring published studies with positive findings [21]. Additionally, the focus on positive psychological outcomes, rather than also considering symptoms of distress, restricts the ability to assess interventions holistically [12, 21]. Moving forward, there is a need for broader, more rigorous reviews that incorporate diverse study designs, include both published and gray literature, and evaluate interventions for their dual capacity to reduce distress and promote wellbeing, thereby maximizing their overall impact on cancer care. Therefore, this review aims to address these gaps by critically assessing the effectiveness of PPIs, ensuring they are grounded in a clear theoretical framework and appropriately tailored to individuals across all stages and types of cancer.

2
Methods
The proposed systematic review was conducted and reported in accordance with the PRISMA‐SR guidelines [23]. The full protocol was developed prior and registered with the International Prospective Register of Systematic Review (PROSPERO): CRD42024546277.
2.1
Search Strategy
The search strategy aimed to identify published, peer‐reviewed studies, and gray literature. A preliminary search on MEDLINE and PsycINFO was performed to explore the present body of literature and establish key terms and medical subject headings (MeSH) within the field of interest. Search terms relating to population and intervention were developed (Table 1). To obtain independent verification, the search strategy was evaluated by, and feedback sought from an academic librarian at Flinders University.
Following the preliminary search, key terms and MESH were subsequently translated and applied across multiple databases: Ovid PsycINFO, Ovid MEDLINE, Ovid Embase, Ovid Emcare, CINAHL, Scopus, and the Cochrane Library. The searches were performed from inception to June 2024. Detailed search syntax for each database is provided in Appendix A (Tables A1, A2, A3, A4, A5, A6, A7). To mitigate the risk of publication bias, gray literature was also sought through targeted keyword searches on Google and Google Scholar, with the first 10 pages of search results reviewed [24]. A review of backward and forward citations for studies published from database inception until June 2024 was conducted. Organizational websites (such as Cancer Council Australia and websites of professional societies/associations in the United States, Europe, United Kingdom, and Australia) were searched for relevant publications. Search parameters were limited to English studies and human subjects, with no restrictions placed on publication date.

2.2
Eligibility Criteria
This review included studies involving cancer survivors or patients at any stage of the disease trajectory, including diagnosis, treatment, remission, and recurrence. Only studies that explicitly identified themselves as PPIs and were grounded in positive psychology theories or methodologies in the development of their interventions were eligible for inclusion. Studies incorporating any form of control group, such as waitlist controls, treatment as usual, or alternative psychological interventions, were included. No restrictions were placed on the type of outcome measures assessed. Detailed inclusion and exclusion criteria are presented in Table 2.

2.3
Study Selection Process
Studies were imported into EndNote 20 software to organize the retrieved results. Covidence software was subsequently used for the screening and selection of relevant articles after duplicate entries were removed. The screening process was conducted in two stages: an initial title and abstract screening, followed by full‐text screening based on the established eligibility criteria. Two independent reviewers (S.A.Y. and A.B.) conducted the screening, and any discrepancies or conflicts were resolved by consultation with a third independent reviewer (L.B.).

2.4
Assessment of Methodological Quality
All studies were independently appraised by two reviewers (S.A.Y. and S.K.) using a modified McMaster Quantitative Critical Appraisal Tool [25], with discrepancies resolved through discussion. This tool, widely used in systematic reviews [26, 27, 28], evaluates quantitative research quality across eight domains: study purpose, background literature, design, sample characteristics, outcome measures, intervention, results, and conclusions. Fourteen criteria were assessed, with responses categorized as ‘yes’ (1 point), ‘no,’ ‘not addressed’ (0 points), or ‘not applicable’ (excluded from the total score). Studies were not excluded based on quality but instead analyzed with consideration of potential bias and methodological rigor to inform the review's findings and interpretation.

2.5
Data Extraction
Data extraction was conducted using a standardized extraction form, detailed in Appendix B (Table B1). The extracted data included the following key components: reviewer initials, study number (as listed in Covidence), author, country of origin, study design, sample size and characteristics, intervention details, positive psychology theoretical framework, outcome measures, quantitative results, and study limitations. The extraction process was independently undertaken by two reviewers (S.A.Y. and A.B.), with each reviewer subsequently cross‐checking the other's work to ensure accuracy and consistency. Discrepancies in data extraction between reviewers were resolved by another reviewer (L.B.).

2.6
Data Synthesis
To synthesize data, results were categorized into three distinct domains. The first domain encompassed positive psychology outcomes, including post‐traumatic growth, a key aspect of flourishing, and the five elements of Seligman's Positive Psychology Framework (PERMA), specifically: positive emotions, meaning, engagement, positive relationships, and accomplishment. Additionally, this domain included measures of subjective wellbeing, such as quality of life (QOL). These constructs were collectively analyzed to determine their contribution to psychological wellbeing and growth, with effect sizes calculated to assess their impact. The second domain focused on psychological disorders and distress, such as depression, psychological distress, and post‐traumatic stress, synthesizing studies that examined interventions aimed at reducing these negative mental health outcomes. The third domain involved physiological outcomes, such as physical and sexual functioning, and pain, examining the broader health effects of interventions and the link between psychological wellbeing and physiological health. Outcomes measured by fewer than three studies were narratively synthesized within their respective domains.
Meta‐analysis was performed using the Comprehensive Meta‐Analysis Version 4 software. Standardized mean differences (SMD) with 95% confidence intervals (CI) were exclusively used in this review, as most studies employed different measurement scales to assess the same outcomes. Given most studies included small sample sizes, Hedges' g was chosen as the appropriate effect size measure due to its correction for small sample bias. The within‐group mean change (Mean) was calculated using the formula “Mean change = Mean after − Mean baseline,” and the standard deviation (SD) of the mean change was determined using the formula “SD change = √[SD2 baseline + SD2 after − (2 * correlation * SD baseline * SD after)].” Hedges' g values were interpreted as 0.8 for large effects, 0.5 for moderate effects, and 0.2 for small effects [29]. Heterogeneity between studies was assessed using the I
2 statistic. For I
2 ≤ 50%, heterogeneity was considered low, and a fixed‐effects model was applied. If I
2 exceeded 50%, indicating high heterogeneity, a random‐effects model was used. For reporting purposes, I
2 values were categorized as follows, based on the guidelines provided by Higgins et al. [30]: 0%–24% as no heterogeneity, 25%–50% as low heterogeneity, 51%–75% as moderate heterogeneity, and 76%–100% as high heterogeneity. Sensitivity analyses were conducted by removing each study one at a time to see if it caused significant changes in the pooled effect size. Based on these thresholds, a random‐effects model was planned a priori and applied where heterogeneity was moderate to high, to account for between‐study variability and enhance generalisability.
Additionally, the overall body of evidence was graded using four of the five National Health and Medical Research Council (NHMRC) FORM framework [31] components: (1) Evidence base, (2) Consistency, (3) Clinical impact, and (4) Generalisability. Component 5 (Applicability to the Australian healthcare context) was not evaluated, given this review is intended for international health care [32]. The data synthesis process was conducted by one reviewer (S.A.Y.) with consultation between reviewers (L.B./T.W./S.K.).

3
Results
The literature search yielded a total of 930 records, including 919 identified from electronic databases and 11 from gray literature and citation searches (see Figure 1). After removing duplicates, 614 records underwent title and abstract screening with 564 records excluded for not meeting the predefined inclusion criteria. Of the 50 full‐text reports sought for retrieval, one could not be obtained and was excluded from the screening process. The remaining 49 were assessed for eligibility, resulting in 33 exclusions (see Figure 1 for reasons). Ultimately 18 studies were included in this review.
3.1
Characteristics of Included Studies
The 18 included studies were published between 2009 and 2023 with the majority (61%) published from 2020 onwards (Table 3). The studies were diverse in design, population, and intervention characteristics, and were conducted across seven countries, including Iran (n = 5) [33, 34, 35, 36, 37], China (n = 4) [38, 39, 40, 41], Iraq (n = 3) [42, 43, 44], Spain (n = 3) [45, 46, 47], the United States (n = 1) [48], the United Kingdom (n = 1) [49], and Portugal (n = 1) [50]. Half the included studies employed quasi‐experimental designs [34, 35, 36, 40, 41, 42, 43, 44, 46], often utilizing pre‐test and post‐test methodologies, while the other half implemented randomized controlled trials (RCTs) [33, 37, 38, 39, 41, 45, 47, 48, 49]. Sample sizes ranged from small (n = 30) [34, 36], to larger‐scale trials (n = 175) [45], with a total of 1382 participants across all studies. The majority of participants were female, with several studies (n = 6) [33, 35, 38, 41, 42, 45] focusing exclusively on patients with breast cancer.
3.1.1
Intervention Characteristics
Interventions ranged between four and 14 sessions, entailing psychoeducation (on acceptance of the disease and challenging negative thoughts), cultivating positive relationships, completing gratitude worksheets, engaging with pleasurable activities, recognition of personal strength, personal growth from the illness experience, and goal setting and attainment [33, 34, 36, 37, 38, 40, 42, 43, 44, 45, 46, 47, 48, 50] (Table 3). The intervention modality varied across studies but typically involved face‐to‐face group sessions [33, 34, 35, 36, 37, 38, 40, 42, 43, 44, 45, 46, 47, 50], with session lengths ranging from 30 [40, 41] to 120 min [36, 44, 45, 46]. Follow‐up periods ranged from providing no follow‐up (56%) [33, 35, 36, 37, 38, 39, 40, 43, 44, 49], 1 month follow‐up [34, 41, 45, 50], to 12 months post‐intervention [46, 47]. Common theoretical frameworks guiding the interventions included Seligman's Positive Psychology therapeutic approach [33, 36, 37, 44, 45], the PERMA framework [38, 39, 40], and Snyder's Hope Theory [48].

3.1.2
Outcome Measures
The included studies employed diverse measures to assess positive psychology components, psychological distress, and physiological outcomes (Table 3). Within positive psychology, post‐traumatic growth was assessed using tools such as the Post‐Traumatic Growth Inventory (PTGI) and Connor‐Davidson Resilience Scale (CD‐RISC) [35, 40, 41, 42, 43, 45, 46, 47]. Positive emotions and engagement were measured using instruments like the Positive and Negative Affect Scale (PANAS), RAND SF‐36, and Cancer Quality of Life Questionnaire (EORTC QLQ‐C30) [36, 38, 45, 48, 50]. Positive relationships, meaning, and accomplishment were evaluated with scales such as the FACT‐B, Differentiation of Self Inventory‐Revised (DSI‐R), and Adult Trait Hope Scale, and [35, 38, 40, 41, 43, 44]. Measures of QOL and psychological wellbeing included the FACT‐B, WHOQOL‐BREF, and Psychological Wellbeing Questionnaire [35, 38, 49]. For psychological distress, depression and anxiety were assessed using the Beck Depression Inventory (BDI‐II), Self‐Rating Depression Scale (SDS), Patient Health Questionnaire‐9 (PHQ‐9) and Hospital Anxiety and Depression Scale (HADS) [33, 34, 38, 40, 46, 47, 48]. Post‐traumatic stress was measured in two studies using the Posttraumatic Stress Disorder Checklist‐Civilian version (PCL‐C) [46, 47]. Within physiological outcomes, physical functioning, sexual functioning, and pain were measured using the RAND SF‐36, FACT‐B, EORTC QLQ‐C30, and Female Sexual Function Index (FSFI) [38, 39, 41, 48, 50].

3.2
Methodological Quality
Overall, the quality of the studies ranged from moderate to high, with 15 studies classified as high quality [33, 34, 36, 37, 38, 39, 40, 41, 42, 43, 45, 46, 47, 48, 50] and three as moderate quality [35, 44, 49]. All studies consistently met the following core criteria: clearly stating their purpose (criterion 1), justifying the importance and providing sufficient background literature to frame the study rationale (criterion 2), reporting results in terms of statistical significance (criterion 7a), and providing appropriate conclusions relative to the results obtained (criterion 8) (Table 4). All but one study [49] adequately addressed reliability and validity of outcome measure tools (Criterion 5a and 5b); therefore, the majority of studies present with reduced risk of both random and systematic bias.
However, the majority of studies failed to justify the sample size utilised [33, 34, 35, 36, 37, 38, 40, 44, 46, 47, 49, 50] and provide sufficient description of the participants within the study [34, 35, 36, 44, 49] (Criterion 4b and 4c) as illustrated in Table 4. Contamination (criterion 6b) was also frequently unaddressed [42, 43, 48] or control measures were not implemented [33, 34, 35, 36, 37, 40, 44, 49], which may reduce internal validity and limit the ability to draw accurate conclusions about intervention effects. Nearly half the studies did not report dropout rates (criterion 7d), introducing potential attrition bias [34, 35, 36, 38, 40, 42, 43, 44].
In summary, while the majority of studies demonstrated methodological soundness in terms of purpose, literature review, and statistical reporting, there were frequent gaps in areas such as sample size justification, participant descriptions, and the control of contamination, all of which may affect the interpretation and reliability of their findings. The inclusion of both high‐ and moderate‐quality studies in this review enabled a comprehensive synthesis but necessitates caution in interpreting the results.

3.3
Effectiveness of Positive Psychology Interventions (PPIs)
3.3.1
Positive Psychology Outcomes
3.3.1.1
Post Traumatic Growth
Eight studies evaluated the effect of PPIs on post‐traumatic growth in 859 cancer participants [35, 40, 41, 42, 43, 45, 46, 47]. The meta‐analysis revealed a significant positive effect of PPIs on post‐traumatic growth, with an overall effect size (Hedges' g) of 0.729 and a 95% confidence interval (CI) of 0.402 to 1.182 (Figure 2). This indicates a moderate to large effect, and the result was statistically significant (p < 0.05). Sensitivity analysis reflected stable results, revealing no change in effect size when each study was removed from the analysis. However, the heterogeneity was high (I
2 = 85.782%), suggesting substantial variability among the included studies.

3.3.1.2
Components of PERMA Model
3.3.1.2.1
Positive Emotions
Six studies consisting of 420 cancer survivors observed significant positive effects [33, 36, 38, 45, 48, 50]. Positive emotions had a large effect size of 1.053 (Hedges' g), with a 95% CI of 0.427 to 1.633, and this result was significant (p < 0.05) (Figure 3). The sensitivity analysis demonstrated consistent results, indicating that the effect size remained stable when each study was sequentially excluded from the analysis. However, heterogeneity was notably high, with an I
2 value of 85.148%, indicating substantial variability across the studies.

3.3.1.2.2
Engagement
The engagement component was assessed in five studies involving a total of 354 cancer participants. Engagement demonstrated a large effect size of 0.941 (Hedges' g), with a 95% CI of 0.400 to 1.481, which was statistically significant (p < 0.05) (Figure 4). The sensitivity analysis showed stable outcomes, with no variation in effect size observed when individual studies were sequentially removed from the analysis. However, heterogeneity was considerable, with an I
2 value of 76.796%, indicating substantial variability across the studies.

3.3.1.2.3
Positive Relationships
The positive relationships component was assessed in seven studies involving 464 cancer participants [35, 38, 40, 41, 43, 44, 48]. Positive relationships demonstrated the largest effect size among all positive psychology components, with a Hedges' g of 1.150 and a 95% CI ranging from 0.470 to 1.830, which was statistically significant (p < 0.05) (Figure 5). Sensitivity analysis confirmed stable results, with the effect size unaffected by the exclusion of any single study. However, the heterogeneity was high, with an I
2 value of 91.059%, reflecting substantial variability across the studies.

3.3.1.2.4
Meaning and Accomplishment
Meaning was measured in nine studies involving a total of 440 cancer participants [12, 34, 35, 37, 40, 41, 42, 43, 48]. The analysis revealed a large effect size of 0.954 (Hedges' g), with a 95% CI of 0.527 to 1.381, which was statistically significant (p < 0.05) (Figure 6). Stability in the effect size was confirmed through sensitivity analysis, as removing individual studies did not impact the results. However, heterogeneity was high, with an I
2 value of 85.242%, indicating considerable variability across the studies.
Accomplishment was only examined in a single study focused on health behavior goals involving 56 cancer survivors [48], and did not demonstrate significant improvements following the positive psychology intervention.

3.3.1.2.5
Subjective Wellbeing: Quality of Life
Quality of life was evaluated in two studies involving 128 cancer participants [38, 49], and demonstrated significant positive improvement in quality of life in both studies following a PPI.

3.3.2
Psychological Disorders and Distress Outcomes
3.3.2.1
Depression
Depression outcomes were measured in four studies involving a total of 269 participants with cancer [33, 38, 40, 48]. The meta‐analysis revealed a large effect size of 1.517 (Hedges' g) with a 95% CI of 0.274 to 2.760, which was statistically significant (p < 0.05), indicating that the PPIs consistently lead to significant reductions in depressive symptoms (Figure 7). Based on the sensitivity analysis, following removal of Tu et al. [40], the p value increased above 0.05, suggesting that without this study, the overall result is no longer statistically significant. This indicates that this study contributed to the overall significance of the results. Additionally, the removal of Fang et al. [38] led to a decrease in the overall effect size (0.784), but the p value remained significant (p < 0.05). This suggests that while Fang et al. may have influenced the effect size, the overall results remain stable and statistically significant following its removal. Furthermore, heterogeneity was high, with an I
2 value of 94.575%, reflecting substantial variability across the studies.

3.3.2.2
Psychological Distress
Psychological distress outcomes were assessed in three studies involving a total of 296 cancer participants [34, 46, 47]. The meta‐analysis produced a small effect size of 0.429 (Hedges' g), with a 95% CI of −0.543 to 1.401; however the result was not statistically significant (p > 0.05) (Figure 8). The sensitivity analysis revealed that the overall effect size for psychological distress remained stable when most studies were removed, with the exception of Fadaei‐Tirani et al. [34] which produced a significant p value of 0.043, suggesting that this study may have had a stronger negative influence on the overall effect size compared to the others. The outcomes exhibited high heterogeneity, with an I
2 value of 92.856%, indicating substantial variability among the studies.

3.3.2.3
Post‐Traumatic Stress
Post‐traumatic stress outcomes were reported in two studies involving a total of 266 cancer survivors [46, 47]. Each study found a significant reduction in post‐traumatic stress following their respective PPIs, indicating that these interventions could alleviate post‐traumatic stress among cancer survivors.

3.3.3
Physiological Health Outcomes
3.3.3.1
Physical Functioning
Physical functioning following a PPI was assessed in four studies involving 278 cancer survivors [38, 41, 48, 50]. The meta‐analysis revealed a small, non‐significant effect size (Hedges' g = 0.421), with a 95% CI of −0.375 to 1.217 and p > 0.05 (Figure 9), indicating that PPIs did not consistently result in improvements in physical functioning. The sensitivity analysis revealed that removing any of these individual studies did not result in a significant change in the effect size. Heterogeneity was notably high (I
2 = 90.151%), suggesting considerable variation across the included studies.

3.3.3.2
Sexual Functioning
Notably, only one study explored the impact of a PPI on sexual functioning in cancer survivors [39]. This study, which included 91 women with cervical cancer, found a significant improvement in sexual functioning.

3.3.3.3
Pain
The effect of PPIs on pain outcomes was assessed in two studies involving 100 participants [48, 50]. The findings showed non‐significant improvements in pain outcomes following the interventions.

3.4
Results Summary
The meta‐analysis suggested that PPIs can enhance post‐traumatic growth, positive emotions, engagement, meaning, positive relationships, and depression with effect sizes ranging from moderate to large and statistically significant results (p < 0.05). Additionally, PPIs led to significant improvements in quality of life and psychological well‐being, highlighting their benefits for subjective well‐being. However, interventions had limited effects on accomplishment, psychological distress, and physical functioning, with outcomes not demonstrating significance. Sexual functioning improved significantly in one study, while pain and physical functioning outcomes did not show significant changes. The overall positive impact is evident, though high heterogeneity suggests variability in intervention effectiveness.

3.5
NHMRC FORM Synthesis
The NHMRC FORM framework was used to synthesize the results of this review (Table 5). The evidence base was rated as Good (B), with 18 studies involving 1382 cancer survivors, including a mix of Level II and Level III studies, most of which demonstrated a low risk of bias. Consistency was graded as Satisfactory (C), reflecting some variation in interventions, outcome measures, and data collection intervals across studies. Despite this heterogeneity, all studies reported statistically significant findings, reinforcing the overall reliability of the evidence. The clinical impact was deemed Good (B), with the majority of studies reporting positive outcomes and clinical significance. Interventions were generally well‐documented, and minimal dropout rates further supported the credibility of the findings. Generalisability was also rated as Good (B), with the studies being representative of the target population, covering diverse regions including the Middle East, US, UK, Europe, and Asia, and including participants at various stages of the disease.
Overall, the grade of recommendation was Good (B), indicating that the body of evidence can be trusted to guide practice in most situations. While some variation across studies was noted, the findings support the use of PPIs in cancer survivorship management.

4
Discussion
The objective of the systematic meta‐analysis review was to investigate the effectiveness of positive psychology interventions (PPIs) for cancer survivors. Findings highlight the potential of PPIs as a promising approach for enhancing psychological wellbeing among cancer survivors. These interventions demonstrated significant improvements in key areas such as post‐traumatic growth, positive emotions, engagement, positive relationships, meaning, and depression. While significant benefits were observed for quality of life (QOL) and sexual functioning, these outcomes were evaluated in a limited number of studies. In contrast, outcomes such as accomplishment, psychological distress, physical functioning, and pain showed limited or inconsistent effects. While the body of evidence largely indicates positive effects from PPIs, this finding is constrained by heterogeneity in intervention designs and methodologies.
Findings from this review highlight the considerable potential PPIs hold in addressing the psychological needs of cancer survivors, particularly in enhancing psychological wellbeing. Unlike traditional psycho‐oncology interventions that predominantly focus on alleviating psychological distress, PPIs aim to foster positive psychological states, such as post‐traumatic growth, positive emotions, meaning, engagement, positive relationships, accomplishment, and QOL which are critical components of flourishing while managing life with the desease [11]. Findings from the present review demonstrate that PPIs significantly improve all components of psychological wellbeing with the exception of accomplishment, which was examined in only one study. Similar to cancer, illnesses associated with significant existential distress and high symptom burden, such as HIV/AIDS, cardiac disease, and multiple sclerosis have demonstrated benefits from PPIs [51]. An RCT among HIV positive men in China reported significant improvement in depression, anxiety, and negative affect over time following a gratitude and social networking‐based PPI in comparison to the control group [52]. Correspondingly, a meta‐analysis of 22 studies involving 1222 participants with cardiovascular disease reported significant improvements in mental wellbeing and reductions in distress following PPIs, both immediately post‐intervention and at follow‐up [53]. Notably, participants with multiple sclerosis, a chronic autoimmune disease known to affect physical and mental health reported significant benefits in hope, positive affect, optimism, state and trait anxiety, general health, and resilience following a PPI [54, 55]. These findings highlight the applicability of PPIs in the adaptation and management of various life‐threatening and progressive illnesses, further reinforcing their role in promoting overall psychological wellbeing in cancer survivors.
Present meta‐analysis further suggests that the effects of PPIs on psychological distress and psychopathology symptoms are less consistent than their effects on psychological well‐being. While PPIs had a modest, non‐significant effect on psychological distress outcomes, their impact on depression was larger and statistically significant. However, sensitivity analyses revealed variability, with Fang et al. [38] study reducing the overall effect size and Tu et al. [40] study contributing to a larger observed effect size. This suggests that the effects of PPIs on depression may not be stable and are heavily influenced by individual study characteristics. These findings are consistent with broader evidence in the field, which has reported mixed results for PPIs in addressing psychological distress and psychopathology across conditions such as cancer and other chronic illnesses [12, 56]. For example, Casellas‐Grau et al. [12] observed that PPIs enhanced quality of life and resilience in cancer patients but had variable effects on distress outcomes, such as depression and anxiety. Similarly, Van Agteren et al. [56] noted that the effectiveness of PPIs in reducing psychological distress in patients with chronic illnesses was often dependent on the specific intervention components and target populations.
The variability in findings may reflect the inherent focus of positive psychology on fostering flourishing and positive emotional experience, which does not directly align with the objectives of distress‐focused interventions [9]. Additionally, the lack of standardization and clear parameters underpinning PPI design likely contributed to inconsistent outcomes [12]. This heterogeneity may in part reflect the diverse foci of the various theoretical underpinnings of different PPIs (van Agteren). Individual differences in subjective evaluations of what a person regards as key to their own functioning well or flourishing may also contribute to variability in program adherence and outcomes. For example, recent research suggests that people vary in the extent to which their happiness is determined by situational life circumstances (bottom‐up), more stable, global perceptions of one's wellbeing (top‐down) or a combination of the two [57]. At a broader level, our findings underscore the important distinction between psychological distress and wellbeing as separate, yet interrelated, constructs, each with its own spectrum and anchors [9, 11]. PPIs may be effective for the promotion and maintenance of wellbeing, whereas distress‐focused interventions may be more suitable for addressing psychopathology. This distinction highlights the importance of tailoring interventions to align with the specific psychological needs and goals of individuals.
Recent research indicates that fear of cancer recurrence (FCR) is one of the most frequently reported concerns among cancer patients and remains a significant unmet need among survivors [58, 59]. Despite evidence indicating that 59% of cancer survivors report FCR, this review did not identify any studies specifically addressing this concern [59]. The presence and severity of physical symptoms, as well as psychological distress, are strongly associated with higher levels of FCR among cancer survivors [60]. Similarly, sexual dysfunction affects a substantial proportion of cancer survivors, ranging from 30% to 100% of women with gynecological cancers, 80% of men with prostate cancer, 50%–75% of women with breast cancer, 24% of individuals with head and neck cancers, and 33% of those who survived childhood cancers [61, 62, 63]. Despite this, only one study included in this review investigated the ability of PPIs to improve sexual function [39]. Shi et al. [39] demonstrated that a self‐administered PPI effectively improved sexual functioning (post 8‐week intervention). The scarcity of research addressing both FCR and sexual dysfunction in the broader cancer population likely arises from the complex and multifaceted nature of these concerns, which encompass psychological, social, and physiological factors. Therefore, future interdisciplinary research is crucial to examine the potential of PPIs in addressing FCR and sexual dysfunction, as these issues are both prevalent and often inadequately treated.
4.1
Clinical Implications
The findings of this meta‐analysis highlight the potential of PPIs as a complementary approach to psycho‐oncology care, particularly in enhancing psychological wellbeing among cancer survivors. PPIs demonstrated significant benefits in areas such as post‐traumatic growth, positive emotions, meaning, engagement, and quality of life, emphasizing their role in fostering resilience and flourishing. While their efficacy in reducing psychological distress is inconsistent and addressing complex issues such as fear of cancer recurrence (FCR) and sexual dysfunction remains underexplored, PPIs may be particularly suited for the prevention and maintenance of wellbeing. To maximize their clinical utility, interventions should be tailored to individual needs, standardized in design, and integrated into multidisciplinary care models to provide a holistic approach to psychosocial care for cancer survivors.

4.2
Strengths and Limitations
This review is presented with several limitations. While this review adhered to best practice guidelines for the conduct and reporting of systematic reviews (PRISMA), there are limitations to consider. Despite efforts to minimize publication bias through gray literature searches and citation searching, the review included only studies published in English, potentially introducing publication and language bias in study selection, as relevant studies in languages other than English were excluded. The included studies had methodological issues, including a lack of double blinding, which can result in placebo and Hawthorne effects (while acknowledging challenges in doing so in these populations and interventions). Furthermore, several included studies reported pre–post change scores without accounting for the dependency between pre‐ and post‐intervention measures, which may have overestimated effect sizes. This analytic approach, while common, is less conservative than using follow‐up scores and should be interpreted with caution [64]. Additionally, this review did not compare the effectiveness of different types of PPIs, stratify findings by cancer stage or time since diagnosis, or by whether outcomes measured were primary or secondary. This was due to the limited number of distinct interventions and the fact that most studies did not restrict their participant populations based on cancer stage, which may have influenced the generalizability of the findings. The absence of a standardized approach across interventions further complicates the ability to draw firm conclusions. Therefore, future research should focus on identifying the optimal parameters for PPIs in cancer populations, including testing potential moderators such as delivery format, intervention length, theoretical framework, cancer type, and stage of survivorship. This would support the development of more tailored and effective evidence‐informed protocols for psychosocial care in cancer survivors.

5
Conclusion
In summary, PPIs largely demonstrated positive outcomes. While high heterogeneity was observed in the PPIs identified in this review, the current evidence base highlights the fundamental role of PPIs in improving wellbeing and ultimately the QOL of cancer survivors. Beyond addressing psychological wellbeing, PPIs may also provide valuable support for survivors facing challenges such as feelings of loss, uncertainty, or role transitions by fostering resilience, cultivating a sense of purpose, and promoting positive psychological states. Additionally, these interventions have the potential to address psychological distress and sexual dysfunction, warranting further research in these areas. Standardizing intervention designs, tailoring approaches to individual needs, and integrating PPIs into multidisciplinary care models will be essential to fully harness their benefits. As cancer survivorship continues to grow, PPIs represent a promising avenue to address the multifaceted psychological needs of this population and promote long‐term flourishing.

Author Contributions
Su Ann Yeoh: conceptualization, methodology, formal analysis, data curation, project administration, writing (original draft), writing (review and editing), visualization. Alice Bowie: data curation, screening, data extraction. Tim Windsor: methodology, supervision, writing (review and editing). Hayley Russell: Supervision. Saravana Kumar: methodology, supervision, writing (review and editing). Lisa Beatty: conceptualization, methodology, supervision, writing (review and editing).

Ethics Statement
The authors have nothing to report.

Conflicts of Interest
The authors declare no conflicts of interest.