Background: Since people with mental illness are more likely to die from cancer, we assessed whether people with mental illness undergo less cancer screening compared with the general population. Methods: In this systematic review and meta-analysis, we searched PubMed and PsycINFO, without a language restriction, and hand-searched the reference lists of included studies and previous reviews for observational studies from database inception until May 5, 2019. We included all published studies focusing on any type of cancer screening in patients with mental illness; and studies that reported prevalence of cancer screening in patients, or comparative measures between patients and the general population. The primary outcome was odds ratio (OR) of cancer screening in people with mental illness versus the general population. The Newcastle-Ottawa Scale was used to assess study quality and I2 to assess study heterogeneity. This study is registered with PROSPERO, CRD42018114781. Findings: 47 publications provided data from 46 samples including 4 717 839 individuals (501 559 patients with mental illness, and 4 216 280 controls), of whom 69·85% were women, for screening for breast cancer (k=35; 296 699 individuals with mental illness, 1 023 288 in the general population), cervical cancer (k=29; 295 688 with mental illness, 3 540 408 in general population), colorectal cancer (k=12; 153 283 with mental illness, 2 228 966 in general population), lung and gastric cancer (both k=1; 420 with mental illness, none in general population), ovarian cancer (k=1; 37 with mental illness, none in general population), and prostate cancer (k=6; 52 803 with mental illness, 2 038 916 in general population). Median quality of the included studies was high at 7 (IQR 6–8). Screening was significantly less frequent in people with any mental disease compared with the general population for any cancer (k=37; OR 0·76 [95% CI 0·72–0·79]; I2=98·53% with publication bias of Egger's p value=0·025), breast cancer (k=27; 0·65 [0·60–0·71]; I2=97·58% and no publication bias), cervical cancer (k=23; 0·89 [0·84–0·95]; I2=98·47% and no publication bias), and prostate cancer (k=4; 0·78 [0·70–0·86]; I2=79·68% and no publication bias), but not for colorectal cancer (k=8; 1·02 [0·90–1·15]; I2=97·84% and no publication bias). Interpretation: Despite the increased mortality from cancer in people with mental illness, this population receives less cancer screening compared with that of the general population. Specific approaches should be developed to assist people with mental illness to undergo appropriate cancer screening, especially women with schizophrenia. Funding: None.
Bibliographical noteFunding Information:
This meta-analysis is the first, to our knowledge, to investigate any and specific cancer screening rates among people with any mental illness: it includes data from over 4·5 million people from all parts of the world, except Africa. Results indicate that people with mental illness had disparities in any, breast, cervical, and prostate cancer screening compared with those in the general population, particularly for breast cancer and in women with schizophrenia. Disparities are apparent across different regions of the world but to a different extent. Given that cancer screening protects from cancer mortality (70% decline in cervical cancer mortality since screening introduction), 29 such disparities might lead to increased cancer mortality in people with mental illness. The results of our meta-analysis extend previous narrative reviews and confirm our hypothesis that people with mental illness undergo less cancer screening than do the general population. Results are in line with Aggarwal and colleagues (19 studies, 106 905 participants), 18 Lord and colleagues (19 studies in total, 18 for mammography, ten for uterine cancer screening, four for colonoscopy, with 1 377 147 participants), 17 and the meta-analysis of breast cancer screening (mammography) by Mitchell and colleagues (24 studies, 715 705 participants), 19 as well as a previous study that showed an association between cancer screening and psychotic disorder, substance abuse, and use of primary or non-psychiatric care. 30 The present data expand previous systematic reviews by including any mental illness and any cancer type in one quantitative evidence synthesis. The underlying reasons that might explain disparities in cancer screening are multiple. First, although many psychiatrists believe that physical examinations should not be done by other professionals, 31 psychiatrists rarely do physical examinations themselves, possibly owing to poor attention to physical health, a shortage of time and equipment, challenges associated with patients who are agitated or otherwise find physical examination difficult, and, possibly, a degree of skill atrophy, especially in more senior psychiatrists. 32 Second, a negative attitude of general practitioners towards cancer screening in people with mental illness has been reported to be associated with an almost 20% increased likelihood of patients' not undergoing cancer screening procedures. 33 Third, nurses, who have a positive attitude towards promoting physical health in people with mental illness, have shown to be more ambivalent when it comes to cancer screening. 34 Such ambivalence might be due to scarcity of training on physical health promotion, and little communication between primary and secondary health-care systems. 35 Fourth, symptoms and impairment in (social) functioning and in cognition might compromise health-care access and use. Fifth, common risk factors might exist for mental illness, cancer, and a reduced likelihood of undergoing cancer screening. Specifically, poverty and low socioeconomic status are known risk factors for psychiatric disorders, 36 while women with lower educational level and lower socioeconomic status have also been reported to know less about cervical cancer and screening. 37 Sixth, patients with mental illness might have difficulties in communicating somatic symptoms, or could not be interested in doing so due to depressed mood or negative symptoms. Seventh, although the WHO 38 and other authors 39–41 have consistently called for optimising the synergy between mental health and primary care, this strong rationale has translated only insufficiently into any actual change in clinical practice. Finally, diagnostic overshadowing, namely clinicians' attributing early somatic symptoms of cancer to underlying mental illness, might also explain why patients with mental illness undergo fewer medical tests. 42 Our findings support the hypothesis that people with schizophrenia suffer from more pronounced disparities compared with individuals with mood disorders. Such differences might be due to persistent functional impairment, which is more frequently present in schizophrenia, 43 as opposed to interepisodic, yet still often suboptimal, improvement of functioning in people with mood disorders. 44 Thus, impairment in social functioning, which is closely related to (social) cognition in schizophrenia, 45 might be responsible for less effective memory, more severe social withdrawal, less medical care help-seeking behaviour, and fewer social contacts, which each contribute to less participation in cancer screening. Nonetheless, we have also shown that any and breast cancer screening is low in people with mood disorders, hence raising public health concerns given the high prevalence of mood disorders. Our results also report that cancer screening disparities were universal across different geographical regions, yet to a different extent. Region-wise subgroup analyses showed that the lowest prevalence of cancer screening in people with mental illness is found in Asia, and the highest in Australia. Paradoxically, Australia also had the highest disparities for some cancer sites, and in people with mood disorders in particular ( table 3 ). This finding can be explained by the fact that disparities are largest where screening in the general population is the highest, as shown by the meta-regression analyses. In other words, if in Australia cancer screening campaigns work brilliantly for the general population, this effect does not hold true for patients with mental illness, who do not benefit as much from health-care progress as do the general population. Differences among regions might also be due to variable measurements of health-care system properties, or cohort-level characteristics. Although most of our hypotheses were confirmed, colorectal cancer screening did not differ between people with mental illness and controls, although the colorectal cancer screening prevalence was the lowest (37·1% vs 48·2–61·9% for the other cancer sites). Thus, cancer screening rate disparities also depend on the rates of cancer screening in the general population. For instance, when the general population suffers from low cancer screening coverage, 46–48 disparities for the mentally ill might not be evident because of a ceiling effect. The present work has several implications, given that cancer screening disparities are highest for those cancers where universal programmes usually exist around the world (ie, breast and cervical), compared with other cancer sites (eg, colon), for which opportunistic screening procedures are done. In other words, while cancer screening campaigns work well in preventing cancer in the general population in countries with national screening programmes, such as in the UK, Italy, and Sweden, among others, this benefit does not seem to generalise to people with mental illness. For instance, although a meta-analysis from 2001 49 showed that more women who received a reminder letter attended cancer screening (OR 1·64, 95% CI 1·49–1·80), and although other strategies seem to promote cancer screening in the general population, 50–53 these approaches might not work for people with mental illness. Therefore, such interventions should involve awareness raising among mental health specialists, and facilitation of communication between primary and tertiary care as well as between specialists in mental health and physical health care, aiming for a close collaboration between mental health and primary care. 38–41,54 The present work has several limitations. The studies included in the present meta-analysis reported on studies from countries with different screening guidelines and with different follow-up durations, so results were nearly always heterogeneous, calling for cautious interpretations, especially of some of the marginally significant findings. In subgroup analyses, some regions were under-represented and Africa was not represented at all. We relied on published data and were able to report results that were adjusted for only a limited number of potential confounders. Furthermore, although controversy exists about the value of screening for prostate cancer, 55 prostate cancer screening was included in our analyses, as reduced uptake in people with mental illness might serve as a marker of reduced access to preventive care in general. Our results apply only to cancer sites for which widespread screening exists. Owing to very limited data on lung cancer, despite high smoking frequencies in the mentally ill, 56,57 our results cannot explain disparities in survival for lung cancer (or other cancers), yet, likely similar barriers to screening and health care access and quality for mental illness will be at play there too. Too few studies were available that differentiated between unipolar versus bipolar mood disorder for us to conduct subgroup analyses of cancer screening across these two subgroups. Additionally, studies adjusting for potentially confounding factors considered heterogeneous types and numbers of covariates. Finally, we did not find any studies on melanoma, although screening for this cancer is common in several countries, including Australia. In conclusion, people with mental illness, including mood disorders, and in particular women with schizophrenia, undergo cancer screening significantly less frequently compared with people in the general population. Such a gap is most pronounced for those cancers for which the general population often receives universal screening based on national programmes. Such disparity might contribute to the life expectancy gap between people with psychiatric disorders and the general population. Asia has the lowest screening rates, and Australia has the highest, and disparities seem to be the highest where the general population is best involved in cancer screening programmes. More studies are needed on lung cancer screening, given the high rates of smoking in people with mental illness. Specific strategies, which should ideally involve mental health departments, general practitioners, and prevention as well as primary care departments, should be tested and implemented in order to fill this important health-care gap and to avoid people with mental illness being left behind in cancer prevention. This online publication has been corrected. The corrected version first appeared at thelancet.com/psychiatry on December 4, 2019 Contributors MS and BS designed the protocol of the study. MS, EF, AK, JF, MF, ED, AM, JIS, BS did the screening and data extraction. MS, BS, CUC run the analyses. MS, AFC, PFP, SK, CUC drafted the manuscript. All authors read, modified, and approved the final version of the submitted manuscript. Declaration of interests We declare no competing interests. Acknowledgments BS is supported by a Clinical Lectureship ( ICA-CL-2017-03-001 ) jointly funded by Health Education England and the National Institute for Health Research (NIHR). Brendon Stubbs is part funded by the NIHR Biomedical Research Centre at South London and Maudsley NHS Foundation Trust. Brendon Stubbs is also supported by the Maudsley Charity, King's College London and the NIHR South London Collaboration for Leadership in Applied Health Research and Care funding. This Article presents independent research. The views expressed in this publication are those of the authors and not necessarily those of the acknowledged institutions. Editorial note: The Lancet Group takes a neutral position with respect to territorial claims in published maps and institutional affiliations.
All Science Journal Classification (ASJC) codes
- Psychiatry and Mental health
- Biological Psychiatry