Abstract
BACKGROUND: One in six people with cancer will develop depression at some point in their care. Untreated depression affects quality of life, cancer care satisfaction and healthcare expenditure. Treatments for this vulnerable heterogenous population should be evidence based and specific. A common sentiment is that psychiatric research does not reflect the prevalence of patients with cancer and comorbid depression and is biased towards certain cancers, but this has not been empirically shown. STUDY SELECTION AND ANALYSIS: A systematic review of studies on psychological and pharmacological treatments for depression in people with cancer was conducted. Of 4621 papers identified from a search of PubMed and PsycINFO up to 27 June 2020, 84 met inclusion criteria (eg, adults with cancer; depression diagnosis; treatment study) and comprised 6048 participants with depression with cancer. FINDINGS: Cancer types are not proportionally represented in depression research in accordance with their incidence. Breast cancer is over-represented (relative frequency in research 49.3%, but 11.7% of global cancer). Cancers of the head and neck and bone and soft tissue were close to parity. All other cancers are under-represented. Representativeness varied 40-fold across different cancers. CONCLUSIONS: The evidence base for depression treatments is dominated by a single cancer. Given heterogeneity in cancer populations (eg, stage of illness; psychological impact; cancer treatments), it is possible that depression treatments may not have the same benefits and harms across all cancers, impeding the ability to offer people with different cancers the best depression treatment. While the dominant opinion within this research field is that a cancer bias exists, this is the first study to demonstrate as such.