Cancer diagnosis and suicide outcomes: Umbrella review and methodological considerations

Background: Suicide outcomes in cancer patients represent a major public health concern. We performed an umbrella review (UR) including all meta-analyses (MAs) and systematic reviews (SRs) published on the association between cancer and suicide outcomes. Methods: Eligible studies were searched in the main scientific databases up to January 23rd, 2021. Eligible MAs/SRs focused on all suicide phenotypes among cancer patients. Evidence of the association was extracted; the credibility and quality of the included studies were evaluated using ad-hoc tools, including "A MeaSurement Tool to Assess systematic Reviews-2-Revised" (AMSTAR-2-R). Results: Six MAs and 6 SRs were included. The standardized mortality ratio of suicide in cancer patients was 1.5 to 1.7-fold higher than in the general population. Risk factors for suicide outcomes among cancer patients were male sex and older age, a cancer diagnosis within the prior year, and some specific cancer sites. Among 107 associations, 90 (84.1%) were supported by high credibility of evidence (class II). However, all studies reported a large heterogeneity (I-2 > 50%) and the majority of them reported considerable heterogeneity (I-2 > 75%). All MAs used random-effects measures. All MAs but one assessed publication bias and only one disclosed it. The majority of MAs/SRs showed critically low quality based on AMSTAR-2-R. Limitations: We could not perform additional analyses due to the limited number of MAs. Conclusions: This UR underlines the inflated risk for suicide among cancer patients. Upcoming, well-designed studies are needed to account for a broader set of variables. Several methodological issues likewise warrant attention.