A COMPREHENSIVE SYSTEMATIC REVIEW OF THE PREVALENCE OF MAJOR DEPRESSION IN PATIENTS WITH BREAST CANCER

Abstract

Introduction: Breast cancer is the most frequently diagnosed malignancy in women worldwide, and major depressive disorder (MDD) is its most consequential psychiatric comorbidity. Reported prevalence estimates vary more than tenfold across the literature, and it remains unclear how much of this dispersion is attributable to genuine population differences versus differences in case ascertainment. This review aimed to quantify and explain the prevalence of major depression and clinically significant depressive symptomatology in women with breast cancer, and to characterise its determinants and prognostic consequences.

Methods: A systematic review was conducted in accordance with PRISMA 2020 guidelines. Eligible designs included randomized controlled trials, cohort, case-control, and cross-sectional studies. Risk of bias was appraised with Hoy, Newcastle-Ottawa, and RoB 2 instruments. Fourteen outcome domains were prespecified. Due to substantial heterogeneity, narrative synthesis with descriptive quantitative pooling (median, interquartile range) was undertaken.

Results: Thirty-four studies comprising >560,000 participants from 22 countries were included. Across 22 studies reporting extractable point prevalence, median prevalence was 31.7% (IQR 21.6–50.5%; range 6.7–93.3%). Ascertainment method was the single most powerful source of heterogeneity: structured diagnostic interview or clinical diagnosis yielded median 14.7% (range 9.3–29.0%), whereas self-report screening yielded 35.6% (range 6.7–93.3%). Depression was significantly more common in breast cancer versus cancer-free women (adjusted HR 1.35, 95% CI 1.32–1.38), with risk maximal in the first post-diagnostic year (sHR 3.23, 95% CI 3.08–3.37) and highest in younger survivors (sHR 4.51, 95% CI 4.19–4.85). Prevalence was greater in metastatic (52.3%) than early-stage disease (21.6–30.4%), in low/middle-income (50.5%) than high-income settings (22.1%), and with comorbid insomnia (HR 9.91, 95% CI 4.92–19.96). Depression was significantly associated with recurrence (HR 1.37–1.60), breast cancer-specific mortality (HR 1.30–1.70), and all-cause mortality (HR 1.54, 95% CI 1.06–2.25). All fourteen prespecified outcome domains demonstrated statistically significant findings.

Discussion: Depression in breast cancer is not a homogeneous entity but a spectrum from transient adjustment dysphoria to persistent syndromal MDD. The threefold divergence between interview-diagnosed MDD and screening-detected depressive symptomatology reconciles the apparently contradictory prevalence estimates. Single-stage self-report screening substantially over-identifies clinical depression and must be followed by confirmatory diagnostic assessment. Risk concentration within the first post-diagnostic year, among younger women, in metastatic disease, and with comorbid insomnia provides an empirically grounded basis for targeted screening. The consistent association between depression and inferior recurrence and survival outcomes, together with a documented 73% treatment gap, elevates depression from a quality-of-life concern to a modifiable prognostic variable.

Conclusion: Approximately one in three women with breast cancer experiences clinically significant depressive symptomatology, and approximately one in seven meets full diagnostic criteria for MDD. Both estimates greatly exceed those of cancer-free women, and the majority of affected patients remain untreated. Two-stage screening anchored on a validated self-report instrument followed by structured diagnostic confirmation, risk-stratified towards younger women, patients with advanced disease, those within the first year of diagnosis, and those with comorbid insomnia, should be embedded as standard in breast cancer care.