Is rumination associated with psychological distress after a cancer diagnosis? A systematic review

Abstract Objective: The aim of this work was to review evidence on the association between psychological rumination and distress in those diagnosed with cancer. Methods: Six databases were searched for studies exploring rumination alongside overall assessments of psychological distress, depression, anxiety, or stress. Results: Sixteen studies were identified. Rumination was associated with distress cross-sectionally and longitudinally. However, once baseline depression was controlled for, the association was no longer seen. The emotional valence of ruminative thoughts and the style in which they were processed, rather than their topic, was associated with distress. Brooding and intrusive rumination were associated with increased distress, deliberate rumination had no association, and reflection/instrumentality had mixed findings. Conclusions: This review highlights that it is not necessarily the topic of content, but the style and valence of rumination that is important when considering its association with distress. The style of rumination should be the target of clinical intervention, including brooding and intrusion.


Background
Each year, an estimated 17 million new cases of cancer are diagnosed worldwide. 1 Receiving a cancer diagnosis represents a set of significant psychological and physical threats. 2,3 Those diagnosed face uncertainties about the future and risk of metastasis, while experiencing disruption to their everyday life. 4,5 Unsurprisingly, as many as 80% of those diagnosed with cancer experience distress. 6,7 Psychological distress represents a range of emotional components, 8 including symptoms of anxiety and depression, which are frequently assessed as measures of distress in cancer populations. [9][10][11][12] Although for many distress resolves over time, for some, distress is experienced long term and can influence treatment outcomes, quality of life, and recovery. [13][14][15][16] Given the impact on psychological and physical health, understanding factors that influence distress remains important in psychosocial oncology research. 17 Identifying potential factors that contribute to distress is important to enable early intervention for those at risk and attempt to reduce experiences of distress. [18][19][20][21] The way in which illness-related material is cognitively processed has been highlighted as a contributing factor of adjustment to chronic illness. 3,20,22 Rumination, a type of perseverative cognition, involves the processing of self-focused information regarding an individual's problems and concerns. 23,24 Ruminative thoughts are conscious and repetitive and are often unified by a common theme. 25,26 Although derived from the same underlying process, rumination is considered multifaceted and can occur in different variations. For example, ruminative thoughts can center on a depressed mood, illness, or work-related issues. Some thoughts may dwell on negative events, and some focus on what can be done about problems. 27,28 The tendency to ruminate in response to a stressor is generally considered to be a trait-like construct or "cognitive habit" used in an attempt to gain insight into the source of concern. 29-31 It has been estimated that around 46% of those diagnosed with cancer experience ruminative thoughts. 32 As a cancer diagnosis can force reevaluation of life goals and create a divide between the healthy and real self, 33 rumination may be engaged as a means to make sense of this disparity.
Although used to gain insight into problems, persistent rumination is often unconstructive and has been considered a vulnerability to psychological distress. 24,34 Models used to understand how rumination may be associated with distress highlight the roles of cognitive deficits in executive control and positive and negative metacognitive beliefs. [35][36][37] Cognitive deficits and beliefs that rumination is helpful or uncontrollable initiate and maintain rumination, leading people to become stuck in a pattern of repetitive thinking in which they struggle to disengage. 38,39 Attention is focused on the sources of threat and negative information that interferes with problem-solving, facilitates further rumination, and ultimately maintains distress. 40,41 The association between distress and rumination has been well established in physically well populations. [42][43][44] Increased symptoms of depression and anxiety have been reported in those who ruminate. [45][46][47] However, distress after a cancer diagnosis represents a very different experience to that within nonclinical populations. People experience a multitude of emotions, including shock, anger, sadness, and fear, while experiencing distress in response to medical procedures, waiting for appointments, and uncertainty. [48][49][50] Rumination may present in a different manner, where negative or distressing thoughts may not always be uncommon or irrational. 51,52 The association between distress and rumination therefore cannot be inferred from research within nonclinical populations and should be explored separately.
Early evidence suggests that rumination plays a role in the psychological adjustment to physical illness. 53,54 Rumination has been associated with greater difficulties in adjusting to a cancer diagnosis, but it has also been associated with positive outcomes such as posttraumatic growth. 32,55,56 As rumination is considered multifaceted, it is thought to encompass both maladaptive and adaptive components depending on the type of rumination. 40,45,57 However, at present there is no agreed-upon conceptualization of rumination. Some have argued that there are many distinct types depending on theme, emotional valence, and style. 25 Distinctions have been made between more reflective and controlled styles of rumination and brooding and intrusive styles, all of which may be differentially associated with outcomes. 55,57 However, comparisons of different types of rumination with distress have not yet been reviewed in psycho-oncology research, and the potential adaptive nature of rumination remains in debate. Identifying what types of rumination are associated with distress is important to identify maladaptive targets for intervention.
With the importance of discovering potential contributors of cancer-related distress, an increasing number of studies have started to explore rumination alongside distress in those diagnosed with cancer. As emerging papers are published, a systematic review of the current literature is timely and informative to both clinicians and researchers. The results of the review could help guide future research and better inform whether rumination is associated with distress in those diagnosed with cancer and how this association is influenced by different types of rumination. If rumination is associated with distress after a diagnosis of cancer, this could be a potential target for intervention.
The primary aim of this review is to systematically identify and evaluate the evidence on whether rumination is associated cross-sectionally and prospectively with psychological distress in those with a current or previous diagnosis of cancer. The secondary aim of this review is to then explore whether different types of rumination (including content, valence, and style) are differentially associated with different distress outcomes.

Protocol and registration
This review was conducted following the PRISMA guidelines 58 and was registered with the International Prospective Register of Systematic Reviews (PROSPERO; registration ID: CRD42021234846).

Criteria for inclusion/exclusion
Studies were included if they quantitatively measured rumination and a form of psychological distress (including anxiety, depression, and stress) in people previously diagnosed with any form of cancer. Due to the novelty of the research, no time frame for diagnosis was included.
Studies meeting the following criteria were included: used a sample of adults (older than 18 years), used a validated measure of rumination, and used at least one validated measure of psychological distress. Studies were excluded if they were not peer reviewed and no grey literature was included.

Search strategy and study selection
Studies were identified by searching the following databases: Embase, Medline, CINAHL, PsycInfo, Web of Science, and Google Scholar (the first 200 articles from the search). This was in accordance with guidelines for conducting psychology reviews. 59 Reference lists of included studies and other relevant reviews were hand-searched to identify other possible eligible studies. Search terms included words relevant to (1) psychological distress (including depression, anxiety, negative affect, and stress), (2) perseverative thinking (rumination), and (3) cancer. See Appendix A for search terms used. Searches were limited to the English language. No date or methodological restrictions were applied. Searches were conducted in March 2021 and updated in May 2022.
All potentially relevant titles and abstracts were downloaded into a reference management database (EndNote) where duplicates were removed. Titles and abstracts of the remaining articles were screened for their eligibility by the first author, followed by full-text records by two reviewers independently. Results were compared and discrepancies were amended by discussion.

Quality assessment
The quality of the included studies was independently evaluated by the reviewers using a modified Effective Public Health Practice Project (EPHPP) Quality Assessment Tool, 60 adapted for use with papers included in this review. Ratings were given across 5 components (sample selection, study design, confounders, data collection methods, and withdrawal). Each component was rated on a 3-point scale of being either weak, moderate, or strong. Ratings were based on information clearly provided within the study articles. Slight adaptions were made to fit the included studies more appropriately (e.g., blinding was omitted from this review as it was not reported within the studies). An overall score was then given based on the scores on each component. Assessments were completed separately by two reviewers and then compared. Discrepancies were amended by discussion.

Data extraction and synthesis
Descriptive and quantitative analysis of data retrieved was conducted. The following data were extracted from each included study: study characteristics (design, measures, type of distress, type of rumination), participant and cancer characteristics (age, gender, site of cancer, stage of cancer, time since diagnosis) and main findings. Findings that measured rumination within a mediation or moderation model were also included. Some studies included multiple styles of rumination and multiple distress outcomes.

Study selection
Sixteen eligible studies were included in this review. Fifteen were identified through the database searches and one additional study through the reference list of a relevant paper. Details of the study selection process are shown in Figure 1.

Study characteristics
There were 10 cross-sectional studies 33,61-69 and 6 longitudinal studies (3 follow-ups at 1, 70 3, 71 and 8 72 months and 3 over multiple time points across 12 months, 73 21 months, 74 and 5 years 9 ). Characteristics and main findings of all included studies are given in Table 1.
Seven studies explored rumination in those diagnosed with breast cancer only, 33,61,65,69,70,73,74 five in samples of mixed cancer, 9,64,[66][67][68] two in colon/ colorectal cancer, 71,72 one in ovarian cancer, 62 and one in gynecological cancer (including ovarian and uterine). 63 In those that reported information on cancer diagnosis, most studies included those in stage 0 to IV or I to IV. Included studies were mixed in time since diagnosis/treatment of their sample (ranged from 1 week postdiagnosis to more than 10 years).

Measures
Across all studies, eight different measures of rumination were used. These included the Ruminative Response Scale (RRS; seven papers including the revised version), Event-Related Rumination Inventory (ERRI; two papers), Chinese Cancer Related Rumination Scale (CCRRS; one paper), Rumination Reflection Questionnaire (RRQ; one paper), Multi-dimensional Rumination in Illness Scale (MRIS; one paper), The Rumination Scale (TRS; one paper), and the Rumination subscale from the Cognitive Emotion Regulation Questionnaire (CERQ; 3 papers including the shortened version). All studies measured trait rumination (no paper assessed current/state rumination or induced rumination); however, one paper also examined differences in rumination within participants. 74 Four types of distress were measured (psychological/emotional distress, depression, anxiety, and stress) using seven different measures. Some papers measured multiple types of distress.  found gender to be a moderator in the association between rumination and anxiety. females with high rumination had lower anxiety than males (B = −0.15, P < .05). Depression, haDs at baseline, between: brooding and reflection were associated with depression (+0.37, P < .001, +0.18, P < .01, respectively). Within: brooding and reflection with depression (+0.31, +0.14, respectively, P < .001).
higher between-person reflection scores predicted higher depressive symptoms, but only when engagement coping was low, not high. at withinperson level, higher reflection scores predicted lower levels of depression when used alongside more disengagement coping than usual. 16. lam et al.  Table 2 presents the component and overall quality assessment scores given for each included study. Based on the global quality ratings, 10 papers were weak, 33,61-66,68,69,71 2 were moderate, 9,67 and 4 were strong. 70,[72][73][74] The main reason for some of the weaker studies was the nature of the design assessment from the quality tool. Due to the constraints of the EPHPP, cross-sectional studies were considered to be weaker in design, which may or not be an exact reflection of the quality of research.

Categorization of rumination
There was considerable heterogeneity in the type of rumination measured based on the high number of measures used. See Table 3 for a visual breakdown of the types of rumination assessed in the included studies.
Most papers used an overall score of rumination, and some explored different styles in which ruminative thoughts were processed (brooding, intrusion, deliberate, and reflection). Additionally, papers varied on the content (topic and emotional valence) of ruminative thought assessed. For example, seven papers measured rumination in response to a depressed mood, 9,61,64,[66][67][68]74 four measured rumination in response to illness/cancer, 33,62,71,73 three measured rumination in response to a stressful event, 63,65,70 one measured rumination of no specified theme, 72 and one assessed rumination in response to depressed mood and cancer. 69 One paper also explored the valence of ruminative content, comparing positive and negative ruminative thoughts. 73 To ease the understanding of findings, results are categorized into overall rumination (cross-sectional and longitudinal findings), style of rumination, and content of rumination.

Overall rumination and psychological distress
Of the 16 studies, nine explored overall rumination scores and psychological distress. Measures of overall rumination did not specify a particular style of rumination, but captured an overall assessment of the amount of ruminative thought experienced by participants. Results are divided into cross-sectional findings and longitudinal findings. Main findings from all included studies are summarized in Table 1.

Cross sectional findings
Seven papers reported results of a cross-sectional association between psychological distress, anxiety, and/or depression with rumination. In one paper, rumination was positively associated with a general measure of psychological distress. 68 In papers correlating rumination and anxiety, most found significant bivariate associations. Rumination was associated with higher anxiety in mixed cancer samples 66,68,71 and in women with ovarian and uterine cancer. 63 These papers assessed anxiety in terms of symptoms over the previous week or month (DASS, HADS, and MHI). Moreover, those with a higher tendency to ruminate were more likely to be classified with clinical anxiety. 68 One study found no association between rumination and anxiety when measuring symptoms of anxiety at that current moment 65 (STAI). Rumination was significantly associated with higher depression in mixed cancer samples 64,66,71 and in women with breast cancer. 65,69 Those with a higher tendency to ruminate were also more likely to be classified with clinical depression. 68 One study, however, found rumination not to be associated with depression in women with ovarian and uterine cancer. 63 It should also be noted that when repeating rumination and distress (depression and anxiety) measurements 3 months later, Salsman and coworkers (2009) did not replicate their significant association at baseline. The paper does not provide further details on this.

Longitudinal findings
Three studies explored overall rumination score and distress longitudinally or with a follow-up. Rumination at baseline was seen to be associated with anxiety and depression at a 3-month follow up 71 and with depression at an 8-month follow up. 72 In those categorized within high-depression groups 1 month later, rumination was seen to be higher relative to those within low-depression groups. 70 However, once baseline depression was controlled for, rumination was no longer associated with depression scores or depression group in either study. 70,72 Style of rumination Some papers explored specific styles of rumination (how ruminative thoughts are processed). This review highlighted four main separate style groups of rumination: brooding, intrusion, deliberate, and reflection/instrumentality. Definitions of these styles are provided below.

Brooding
Six papers explored "brooding," a style of rumination involving passive judgmental thoughts and self-blame. Two types of brooding were highlighted: brooding and depressive brooding. Depressive brooding was associated with anxiety and depression. 61 Similarly, brooding was associated with higher anxiety, depression, 33,61,64 and stress 33 in women with breast cancer and with depression in those with mixed types of cancer. 67 In longitudinal analyses, brooding was found to be associated with depressive symptoms at baseline and 3, 9, and 21 months later in women with breast cancer 74 and with anxiety and depression during a 5-year follow-up in a mixed cancer sample. 9 When controlling for reflection, brooding was associated with depression, 74 and when controlling for instrumentality and intrusion, brooding about illness was associated with higher depression, anxiety, and stress. 33 In addition, higher brooding at the within level (changes over time) was associated with higher depression cross-sectionally and prospectively when controlling for within levels of reflection. 74

Intrusion
Two papers assessed intrusive rumination, defined as ruminative thought that is unintentional and difficult to control. Intrusive rumination of cancer-/illness-related information was associated with psychological distress when deliberate rumination was controlled for 62 and stress when brooding and instrumentality were controlled for. 33

Deliberate
One paper assessed deliberate rumination, 62 the act of ruminating at will and being in control of when rumination is engaged. Deliberate rumination was found to be associated with psychological distress. However, this was no longer significant when intrusive rumination was controlled for.

Reflection/instrumentality
Five studies assessed reflection/instrumentality, the purposeful turning inward in an attempt to problem-solve. Findings of the association between reflection and distress were mixed. Reflection was not associated with depression in patients with colon cancer at baseline or 8 months later. 72 When controlling for brooding and other coping strategies, within-and between-person reflection scores were not associated with depression. 74 Instead, instrumentality around illness was found to be associated with lower depression and stress scores when intrusion and brooding were controlled for. 33 With no other styles of rumination controlled, reflection was associated with higher depressive symptoms in a sample of patients with mixed types of cancer 64 and with higher anxiety and depression in those with breast cancer. 61 Similarly, when not controlling for brooding or coping strategies, Wang and associates (2020) did find reflection to be associated, albeit weakly, with higher depression at baseline (3 months after treatment). However, this association became weaker 3 and 9 months later and nonexistent after 21 months.

Content of rumination
No stark dissimilarities were found between studies that assessed different topics of rumination content. For example, rumination in response to a depressed mood, a stressful event, and a cancer diagnosis were all similarly associated with psychological distress. One study, however, found the valence of rumination content to be differentially associated with distress. Lam and colleagues (2013) found that those who ruminated about negative cancer-related content were more likely to be categorized as having high stable levels of anxiety and depression over 12 months. Those who ruminated about positive cancer-related content were more likely to report low levels of anxiety and depression (they were less likely to have depression or anxiety).

Other processes involved in rumination and psychological distress
Some papers also explored other factors associated with distress alongside rumination. Rumination was associated with depression in those with high levels of fear of recurrence, but not those with low levels of fear of recurrence. 66 Similarly, higher reflective rumination was associated with lower depression in those using disengagement coping and higher depression in those who used engagement coping. 74 Gender was also found to moderate the association between brooding and anxiety. Men with high brooding reported greater anxiety than women. 9

Rumination mediates association between psychological distress and other variables
Depressive rumination mediated the relationship between harm/loss appraisal and depressive symptoms. 69 Low levels of depressive brooding mediated the relationship between self-compassion and distress, 61 age and depressive symptoms, and the relationship between thanksgiving prayer and depressive symptoms fully. 67 Rumination (including brooding and reflection also) was found to mediate the association between dysfunctional attitudes and depressive symptoms. 64 Yet, in the same study dysfunction attitudes were also seen to mediate the relationship between rumination and distress.

Discussion
This systematic review is the first synthesis of published literature exploring the cross-sectional and prospective association between rumination and distress in those diagnosed with cancer. The majority of studies reported a significant, positive association between rumination and distress; however, in longitudinal studies that controlled for baseline depression this association was no longer seen. In relation to the second aim of this review, the valence of ruminative thought rather than the topic was found to be associated with distress. Moreover, more negative styles such as brooding and intrusion were associated with higher distress, whereas associations between distress and deliberate, reflection, and instrumentality styles were mixed.

Overall rumination and distress
Overall rumination was associated with clinical and nonclinical psychological distress cross-sectionally and longitudinally. In general, there was a positive association between overall rumination and trait anxiety and depression (symptoms of distress over a period of time, e.g., the previous week or month). Rumination was not, however, associated with state anxiety. This is not surprising as the included papers in this review all assessed trait rumination and not whether participants were ruminating at the time of the study. Those with a trait tendency to ruminate do so at certain times, not necessarily all the time. 75 Therefore, it may be that some aspects of distress, such as anxiety, are experienced only during times of rumination which would be captured by trait, not state, measures of anxiety. However, as only one paper of weak quality assessed state anxiety and no studies explored state or induced rumination, this association remains unclear.
Contrary to the papers that found an association between overall rumination and depression, one cross-sectional study did not 63 , and another failed to replicate their original association found 3 months prior. 71 This may have been due to the way rumination was assessed. Kulpa and colleagues authored the only study to use a shortened subscale measure of rumination. Although initial validity was shown, 76 its reliability and validity has since been questioned with one of the two items considered as tapping into curiosity rather than rumination. 77 Similarly, Salsman and colleagues used a measure that in their own paper had questionable and adequate internal consistency, has reported weak consistency in previous research, 78 and has been critiqued as containing items reflecting worry rather than rumination. 79 These measures may not have captured the same rumination construct as the other included papers.
Additionally, an important caveat to the significant association between overall rumination and depression was seen in the longitudinal studies that controlled for baseline depression. When baseline depression was controlled for, rumination was no longer associated with depression at follow-up. Some theoretical models define rumination and depression as having a reciprocal relationship, where rumination forms a part of depression as well as being a vulnerability factor. 80 Rumination is experienced in response to a negative mood, which it then prolongs in a cyclical manner. 81 As such, removing the shared variance of depression and rumination may affect their association in longitudinal studies. However, only two of the six longitudinal studies in this review controlled for baseline distress. Future research should explore whether rumination is independently associated with distress or whether it is the shared variance responsible.

Type of rumination
The findings from this review suggest it may not be the topic of ruminative thoughts that is key when considering distress in cancer, but their style and valence. The main styles of rumination apparent in this review included brooding, intrusion, deliberate, and reflection/instrumentality, consistent with literature on depressive and posttraumatic rumination. 57 Intrusion and brooding are believed to overlap to form maladaptive rumination, whereas reflection and deliberate may overlap to represent more adaptive forms. 82 In line with this presentation and previous research (e.g., Javaid et al. 83 ; Morris-Shakespeare and Finch 84 ), brooding and intrusion were more consistently associated with increased distress compared to deliberate rumination. Reflection, on the other hand was more complex and inconsistent; with some research showing positive associations with distress, while others demonstrated no association. This is in line with the current debate in the literature on the adaptive nature of reflection. This review found reflection, on the most part, not to be associated with anxiety and depression. This is supported by Guan and associates (2021), who found intrusion and brooding, not reflection and deliberate rumination, to be associated with depression and anxiety in cardiac patients.
Ruminating about negative cancer-related content was associated with higher depression and anxiety compared to ruminating about positive content. This may be because when ruminating about negative material, attention is focused on negative content which increases emotional arousal. 85,86 Ruminating on more positive content may not elicit the same distress response. Some evidence has suggested that positive rumination may even be protective against depressive symptoms by buffering against negative outcomes of rumination. 87 As most measures used in this review tap into rumination on negative affect, that is, depressive rumination, rather than on positive affect, 88 the valence of thoughts could determine whether distress is maintained.

Rumination and other factors
Factors alongside rumination were explored to explain more about its association with distress. Moderators included fear of recurrence, engagement/disengagement coping, and gender. Rumination was associated with depression in those with high fear of recurrence, but not low, while brooding was associated with anxiety in men with high rumination, but not women. Higher reflective rumination was associated with lower depression in those using disengagement coping, and higher depression was found in those who used engagement coping. This suggests that rumination can exacerbate issues in certain genders or those with an underlying vulnerability such as fear of recurrence, but it also suggests that some styles can have a protective or harmful effect when used in combination with other coping strategies.

Quality of research
The quality of the included studies was variable. Quality was mostly compromised by the use of a cross-sectional design. More research is needed to explore the association between rumination and distress prospectively and over time in those diagnosed with cancer. Longitudinal research should also consider controlling for baseline distress to be able to decipher whether rumination is independently associated with distress or whether it is the shared variance that is responsible.
Additionally, some papers used the CERQ which, although validated, is not the most comprehensive measure of rumination. 77 Many papers also used depressive rumination measures which may have some overlap with depression and/or negative emotion. 28,69 Depressive thoughts may not be uncommon after a diagnosis of cancer and, as such, measures that focus on depressed mood may not be completely suitable. Future research could benefit from using more distinct rumination measures when examining distress.

Study limitations
Some limitations of this review should be acknowledged. There was much heterogeneity in the measures used to assess rumination, which made comparisons between studies more difficult. To help synthesize the findings, results were qualitatively grouped into types of rumination (overall rumination, style, and content). It could be argued that some measures fit more appropriately to their allocated group than others. Although they are distinct, there is much overlap between the different styles of rumination. 82 Instrumentality and reflection may involve deliberate rumination, representing purposeful engagement in ruminative thought. 33 Nevertheless, the layout provides a clearer way of understanding how different styles and content of rumination may be differently associated with distress.
As this is the first time research on rumination and cancer distress has been synthesized in this way, the current review included all types of cancer at any points after diagnosis. Although no clear differences by site of cancer or duration since diagnosis appeared in this review, there may be nuances missed in the distress or rumination experience. Likewise, age and gender have been shown to be influential in rumination, 89,90,91 and differences in the relationship between rumination and depression have been seen across ethnicities. 92 As participant age and ethnicity were not controlled for and the studies included mainly women, this may have impacted the results.

Clinical implications
The findings of this review suggest that having a ruminative thinking style is associated with psychological distress including depression and anxiety after a cancer diagnosis. Therefore, rumination could be used to identify those at risk for distress or as a potential target of interventions.
The findings highlight the importance of the style in which ruminative thoughts are processed when looking at distress. From this review, there appear to be both maladaptive and adaptive forms of rumination, which may contribute to differential outcomes in those diagnosed with cancer.
This review identified four main styles, supporting previous research. 57 As different styles may increase, decrease, or have no effect on distress, it may be too simplistic to aim to solely reduce rumination. Interventions may seek to avoid reducing rumination as a whole and instead be designed to reduce the maladaptive styles of rumination, particularly brooding and intrusion, and rumination of negative valence. Interventions may also seek to work with patients to change their rumination style from brooding and intrusion to a more deliberate and instrumental style. Components of preexisting interventions used in oncology such as acceptance and commitment therapy could be tailored to include styles of rumination when considering which thoughts are helpful and which are not, rather than reducing all rumination. It would be useful to map existing interventions in psycho-oncology to see where the greatest benefit may be for patients. For example, our previous research showed that imagery rescripting could be a powerful tool to address intrusive thoughts in people diagnosed with cancer 93 and may be relevant for those experiencing an intrusive rumination style.

Conclusions
This review presents an overview of the current research exploring rumination and distress in those diagnosed with cancer. The main and consistent finding was that emotional valence and style of rumination are important when interpreting the association between rumination and distress. Ruminating on negative cancer-related content and maladaptive styles such as brooding and intrusion seem to be uniquely associated with distress, including anxiety and depression. In contrast, ruminating about positive content and in a deliberate or instrumental manner may not be as harmful. More research is needed to decipher the differences between styles of rumination and distress after a diagnosis of cancer within the same sample, and more longitudinal research is warranted to explore changes in this association over time.

Funding
The author(s) reported there is no funding associated with the work featured in this article.