People with mental illness die earlier than those in the general population and the main reason for these early deaths is due to physical health conditions (Brown et al, 2010). Instead of decreasing over time, this life expectancy gap is actually increasing (Hayes et al, 2017).
Although the incidence of cancer is the same between people with mental ill health and the general population (Kisely et al, 2008), people with mental illness have been found more likely to die from cancer than those without (Nordentoft et al, 2013). There are several possible reasons to explain this finding. Firstly, people with mental ill health may be less likely to have surgical interventions, radiotherapy and receive fewer chemotherapy sessions. They may also be less tolerant of intensive treatment programmes with significant side effects (Baillargeon et al, 2011). Finally they may be less likely to undergo cancer screening resulting in a poorer prognosis when cancer is diagnosed due to diagnosis being at a later stage (Firth et al, 2019).
To explore whether people with mental illness are less likely to undergo cancer screening, Solmi et al. (2019) published a systematic review and meta-analysis on exploring differences in cancer screening in people with mental illness across the world compared to the general population. The authors hypothesised that people with mental illness are disadvantaged in cancer screening compared with the general population and that people with schizophrenia are the most disadvantaged. They also hypothesised that this would be regardless of the type of cancer or where the person was living.
The authors searched for observational studies of cancer screening. The studies needed to include people with mental illness and report the prevalence of cancer screening in people with mental illness or a comparative measure between people with mental illness and the general population. The study could involve any type of mental illness and any type of cancer.
Two databases were searched from inception to May 2019. No language restrictions were applied and the study could be in any country. The database search used terms relating to mental health and terms related to cancer and cancer screening. Reference lists were also searched.
The authors extracted data from the included studies which they used to carry out a meta-analyses of any cancer screening in people with mental illness compared to the general population and specific cancer screening compared to the general population. A sensitivity analysis was conducted limiting the meta-analysis to studies where mental illness had been defined by any version of the DSM-5 or ICD-10 criteria. Subgroup analyses were conducted comparing a) patients with schizophrenia to patients with mood disorders, b) studies from different regions and c) studies that on cancer screening programmes to studies on opportunistic screening. Finally the authors carried out a meta-regression to test whether any screening gap between people with mental illness and the general population increased with increased screening rates in the general population.
The authors identified 3,710 studies and screened 145 full-texts, 46 studies were eligible for inclusion (reported in 47 publications). The included studies involved 4,717,839 participants (501,559 patients with mental illness, and 4,216,280 controls) of which about 70% were female. All continents except for Africa were included and age ranged from 18-79 years. Types of cancers included were; breast, cervical, colorectal, lung, gastric, prostate and ovarian. Four studies focused on depression, six on schizophrenia, 14 on mixed mental disorders that reported results by diagnosis, and 12 on mixed mental disorders without reporting results by diagnosis.
- Results from meta-analyses indicated that people with mental illness are less likely to undergo screening for cancer than the general population and this is particularly true of women and people with schizophrenia.
- Sub-group analyses showed that whilst people with mental illness were less likely to receive screening than the general population in any part of the world, the difference was greatest in Asia and the least difference was found in Australia.
- Differences in screening by type of cancer showed that colorectal cancer screening did not differ between people with mental illness and the general population. However, disparities in screening were greatest where there was a good uptake of screening in the general population, and in colorectal cancer the uptake in the general population is also low.
New findings by Solmi et al. (2019) indicated that people with mental illnesses were less likely to receive screening for cancer compared to the general population. This was more evident among women and people diagnosed with schizophrenia. The authors concluded that action needs to be taken to promote cancer screening among these sub-groups. Cancer screening programmes that work for the general population do not appear to work as effectively for people with mental illness. Therefore, these programmes may need tailoring to ensure better uptake amongst people with mental illness.
Strengths and limitations
The strengths of this study are; it includes a large number of people (4·5 million) from all continents except Africa, and that it includes different types of cancer and different types of mental illness. Providing information on disparities in cancer screening across a variety of cancers and mental illness allows the authors to draw conclusions about cancer screening in people with mental illness more generally rather than drawing conclusions on disparities in screening for a single type of cancer or individual mental illness.
One of the limitations of this study is that the screening guidelines and follow-up periods varied across the different countries which led to the results being heterogeneous. This means that the findings should be interpreted with caution, especially where the differences were small. In addition, some regions were under-represented and none of the studies included Africa, which means that we cannot generalise the results of this study to Africa as it may be that there are significant differences in screening procedures in Africa that could affect how people with mental illness are screened. Finally, only published data was included in the review, which meant that not all forms of cancer were represented and that it was not possible to compare unipolar and bipolar disorders.
Implications for practice
- Cancer screening programmes that have proved to be effective in the general population do not appear to be as effective for people with mental illness.
- The implications from the findings by Solmi et al. (2019) are that action is needed to promote cancer screening in people with mental illness.
- People with mental illness may need specific tailored interventions and these need to be developed and evaluated in order to determine which interventions are the most effective.
- People with mental illness die earlier than those in the general population and one of the ways this disparity may be reduced is through developing effective cancer screening programmes tailored to people with mental illness.
Conflicts of interest
Solmi, M., Firth, J., Miola, A., Fornaro, M., Frison, E., & Fusar-Poli, P. et al. (2019). Disparities in cancer screening in people with mental illness across the world versus the general population: prevalence and comparative meta-analysis including 4 717 839 people. The Lancet Psychiatry, 7(1), 52-63. doi: 10.1016/s2215-0366(19)30414-6
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Hayes JF ML, Walters K, King MB, Osborn DPJ. (2017) Mortality gap for people with bipolar disorder and schizophrenia: UK-based cohort study 2000-2014. 2017;211(3):175-181.
Kisely S, Sadek, J., MacKenzie, A., Lawrence, D., & Campbell, L. A. (2008) Excess Cancer Mortality in Psychiatric Patients. 2008;53(11):753-761.
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