Psychological flexibility and inflexibility in people with cancer: a meta-analysis of associations with distress and quality of life, and a cross-sectional study exploring psychological flexibility in relation to psychological adjustment, distress and health-related quality of life among people with breast cancer

BACKGROUND AND OBJECTIVES: Psychological adjustment to cancer remains an area of clear clinical relevance, with substantial proportions of people experiencing distress and reduced quality of life. Although psychological flexibility, is increasingly viewed as a transdiagnostic construct and a key mechanism targeted across process-based therapies, its relationships with cancer-related adjustment responses, distress and quality of life remain underexplored. Understanding these pathways will contribute to the development of targeted, evidence-informed interventions that address the individualistic and contextual nature of cancer-related psychological adjustment. This portfolio comprises two independent studies: the first explores the distinct relationships between psychological flexibility and inflexibility with distress and health-related quality of life, and the second examines whether psychological flexibility may act as a buffering or associational variable between maladaptive adjustment responses, distress, and health-related quality of life. METHODS: The first study systematically reviewed 51 studies (50 included in meta-analyses) examining associations between psychological inflexibility or flexibility and distress or quality of life across adult cancer populations. The second study was a cross-sectional study in a sample of 100 adults with breast cancer which assessed how psychological flexibility may contribute to the relationships between maladaptive adjustment responses (helplessness-hopelessness, anxious preoccupation, cognitive avoidance), distress, and health-related quality of life. RESULTS: Four meta-analyses revealed significant correlations in theoretically expected directions: greater psychological inflexibility was associated with higher distress and lower quality of life, while greater psychological flexibility was associated with lower distress and higher quality of life. Helplessness-hopelessness emerged as the largest predictor among adjustment responses and psychological flexibility of both greater distress and lower quality of life. Psychological flexibility moderated only the relationship between anxious preoccupation and distress, suggesting that additional factors may contribute to these relationships. Distress remained independently associated with quality of life regardless of psychological flexibility. CONCLUSION: Collectively, these studies advance the understanding of the possible distinction between psychological flexibility and inflexibility, as well as how psychological flexibility may operate as a process within the relationship between certain illness-adjustment responses and distress. Both psychological flexibility and inflexibility showed significant associations which differed in magnitude with distress and quality of life across various cancer samples (Study 1). However, the moderating effect of psychological flexibility may be limited and more pronounced for anxiety-related adjustment responses (Study 2). Psychological flexibility and inflexibility may represent distinct processes that warrant greater conceptual clarity. Together, these findings suggest that clinical practice may benefit from attending to transdiagnostic processes such as psychological flexibility and inflexibility alongside illness-specific adjustment responses.