Background/Objectives: A cancer diagnosis and its subsequent treatment constitute one of the most psychologically demanding experiences a patient can face, and decades of psycho-oncology research have documented an elevated burden of depression, anxiety, and related conditions in this population. Reported prevalence figures nonetheless vary enormously between studies—a 2011 meta-analysis by Mitchell and colleagues, for instance, arrived at pooled depression estimates roughly half those reported in some subsequent work—complicating clinical decisions about who should be screened and how intensively. The present narrative review with preliminary quantitative synthesis set out to chart this variability directly: to assemble a cross-section of the international literature on depression, anxiety, post-traumatic stress disorder (PTSD), insomnia, and suicidal ideation in oncology patients to quantify how far pooled estimates diverge from one another when treatment setting, tumour type, and assessment instrument are allowed to vary freely, and to lay the empirical groundwork for a subsequent, fully systematic review by the author group.
Methods: Consistent with the exploratory aims stated above, eligible primary studies were located through web-based literature searching and citation chaining rather than exhaustive querying of bibliographic databases; the search was therefore not conducted, and is not reported, as a PRISMA 2020-compliant systematic review. Cross-sectional or baseline cohort studies reporting original prevalence figures for at least one of the five outcomes above, in patients with a histologically confirmed malignancy, including adult and paediatric/adolescent patients, who were undergoing or had completed treatment, using a named validated instrument, were retained. Where two or more studies addressed the same outcome, a random effects pooled proportion (DerSimonian–Laird estimator, Freeman–Tukey double arcsine variance stabilisation) was computed in Python as an illustrative, not definitive, summary statistic, alongside Cochran’s Q and I
2.
Results: Twelve studies conducted across nine countries were retained, contributing fourteen outcome-level data points. The illustrative pooled prevalence of depression was 45.6% (95% CI: 29.5–62.3%; k = 3; I
2 = 91.2%) and of anxiety 44.1% (95% CI: 32.7–55.8%; k = 4; I
2 = 90.5%)—both considerably above the double-digit figures reported in earlier interview-based meta-analyses, reflecting the self-report screening instruments and, in several instances, lower-income treatment settings represented in the present sample. Pooled PTSD prevalence was 17.0% (95% CI: 7.3–29.7%; k = 3; I
2 = 91.8%) and pooled insomnia prevalence 38.0% (95% CI: 24.5–52.6%; k = 3; I
2 = 86.7%). A single Chinese multicentre study of 509 women with advanced breast cancer reported suicidal ideation in 22.8% of respondents; this figure is reported descriptively only, is not pooled, and should not be extrapolated to oncology patients generally.
Conclusions: Even acknowledging its exploratory character, this synthesis reinforces a conclusion already well established in psycho-oncology: a substantial minority, and on some metrics close to half, of patients receiving cancer treatment report clinically significant psychological symptoms, with figures highest for depression and anxiety in the self-report studies assembled here. The magnitude of between-study heterogeneity observed for every outcome, however, argues strongly against treating any single percentage—ours included—as a stable population estimate; tumour type, treatment phase, country income level, and instrument choice all plausibly move the figure by a considerable margin, and disentangling these influences is the explicit purpose of the fully systematic review the author group is now undertaking; the present figures should be read as hypothesis-generating inputs to that forthcoming systematic review, not as stand-alone prevalence estimates suitable for direct clinical or policy use.
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