It is now well-established that mental illness significantly contributes to a reduced lifespan, as evidenced by longitudinal studies (Harris & Barraclough, 1998; Lozano et al, 2013). Extraordinarily, there is now data showing that mortality rates are getting worse over time (Hoang et al, 2011). A global study spanning 187 countries, aptly titled the Global Burden of Disease Study (which we featured last year on the Mental Elf), found that between 1990 and 2010, there was an increase of 94,000 premature deaths secondary to mental illness, producing a total of 232,000 (Whiteford et al, 2013).

It is worth noting that three quarters of these deaths were related to substance abuse, sadly often comorbid with mental illness and likely to increase the risk of suicide (Najt et al, 2011). In fact, suicide is a common cause of death in this population generally, and is more prevalent in countries with advanced healthcare systems (Whiteford et al, 2013).

Altogether, it’s clear that mortality rates amongst the mentally ill are a significant concern, and the challenge to preventive medicine is to increase the efficiency in delivery of evidence-based medicine to those with substance abuse and mental disorders. Part of the challenge is identifying exactly which disorders present the greatest risks and hence where resources should be prioritised.

Unfortunately, the last review attempting to evaluate this was conducted 16 years ago (Harris & Barraclough, 1998), making it an appropriate time for an update. Published in June of this year, an article in World Psychiatry by Edward Chesney and colleagues presents just that (Chesney et al, 2014).

The authors summarise that:

With the increase in evidence over recent decades and contrasting estimates in meta-analyses, an updated review is required. This will enable clinicians to prioritize interventions based on the comparative risks of mortality across disorders, researchers to identify where gaps exist in the literature, and commissioners and policy makers to target resources more effectively.

Methods

To find pooled all-cause mortality and suicide statistics between January 1, 1998 and February 19, 2014, the authors conducted a meta-review, which is a review of many systematic reviews and meta-analyses. Systematic reviews encompass many studies selected according to strict criteria, while meta-analyses statistically analyse findings taken from studies all examining the same thing. If this sounds at all confusing, it’s because meta-reviews are a bit like scientific Russian dolls, presenting a summary of findings from many other summaries of findings, hence the ‘meta’ bit!

Interestingly, the literature search was conducted using Google Scholar. While some would certainly frown on using the academic arm of Google’s empire (Giustini & Boulos, 2013), recent studies have shown it to be capable of producing search results comparable (or better) to those of more dedicated scientific databases such as PubMed (Gehanno et al., 2013; Shariff et al., 2013). Perhaps we are witnessing a changing of the guard for future literature searches?

The search included the following diagnoses: Depression, anxiety, bipolar disorder, schizophrenia spectrum disorders, eating disorders, learning disability and autistic spectrum disorders, childhood behavioural disorders, personality disorders, dementia, substance use disorders, alcohol use disorder and smoking.

You may notice that smoking is included in that list. The authors propose that since it is commonly accepted that smoking is an important target for preventive medicine, should mental illness show similar mortality rates this would underline the danger to public health that mental illness represents.

Each review was rated using the Assessing the Methodological Quality of Systematic Reviews (AMSTAR) measure, a way of empirically gauging the quality of a review according to eleven yes/no criteria.

Extracted from these reviews and meta-analyses were different estimates of mortality associated with mental illness. Most studies employed Standardised Mortality Ratios (others used Relative Risk or Odds Ratios). A number higher than 1.0 represents increased numbers of observed deaths in those with a mental disorder than would be expected in healthy populations.

After exclusions, 20 systematic reviews and meta-analyses were included, covering 20 disorders, over 1.7 million individuals, and over a quarter of a million deaths.

Seven out of 20 reviews had a low quality rating score, 12 had a medium score, and only one achieved a high quality rating. Common omissions were lack of testing for publication bias, not searching grey literature (i.e. not published in a journal, such as government reports), and not having two data extractors.

Results

Gaps in the literature

• There were significant gaps in the literature regarding all-cause mortality for:
  • Bipolar disorder
  • Anxiety
  • Personality disorders
  • ADHD
  • OCD
  • PTSD
• As well as suicide risk
  • Cocaine use
  • Amphetamine use
  • Autism
  • Dementia
  • ADHD

All-cause mortality

• All disorders had an increased risk of all-cause mortality compared with the general population
• Substance abuse and anorexia had the highest mortality risks
  • 14.7 for opioid use
  • 4 to 8 for cocaine use
  • 6.2 for amphetamine use
  • 5.9 for anorexia
• Mortality risks for schizophrenia and autism were at least as high as heavy smoking

Suicide risk

• Borderline personality disorder, anorexia nervosa, depression and bipolar disorder had the highest suicide risks

Reductions in life expectancy:

• 7-11 years for a single depressive episode or recurrent depressive disorder
• 9-20 years for bipolar disorder
• 9-24 years for substance use
• 10-20 years for schizophrenia
• 13-22 years for personality disorders
• 8-10 years for heavy smoking

Conclusions

The authors concluded:

The impact on mortality and suicide of mental disorders is substantial, and probably poorly appreciated as a public health problem. The scale of the unmet needs complements the social burden and costs of mental disorders.

Discussion

This may well be the first meta-review of all-cause mortality and suicide risks in mental disorders conducted so far. It would appear that all of the major disorders, bar those for whom data was not available, carry a substantial mortality risk on a par with or greater than heavy smoking, significantly reducing life expectancy and increasing the risk of suicide. These findings are staggering, particularly when using heavy smoking as a benchmark.

The authors do indicate however that the majority of the figures are likely derived from inpatient data, referring to those who have been hospitalised at least once due to mental illness. In this sense, the figures are more representative of an extreme, so are less likely to apply to those living in the community who have never been hospitalised.

The study is also rather broad in scope (necessarily). All-cause mortality covers death relating to any possible cause, which includes suicide but also lifestyle-related physical illness (e.g. obesity is common in schizophrenia). It would be fascinating to know the different causes of death overall, as well as by disorder.

We’re only beginning to understand the link between physical and mental illness for example, and to date this remains a chicken and egg-like quandary, e.g. chronic stress appears to have an immunosuppressant effect, which in turn may factor into the onset of mental illness (Capuron & Miller, 2011). Teasing apart the causal relationships and specific risk factors in each disorder would be hugely impactful, if only to help change the perception that mental illness is somehow less important than physical illness, as this review clearly demonstrates is not the case.

Undoubtedly, this review is a stepping stone onto more fine-grained work and a call to arms for funders and researchers in preventive medicine.

Limitations

• As mentioned, the general quality of the literature was rather poor, typically featuring a lack of testing for publication bias and a lack of a second data extractor when conducting literature searches (this review employed a second data extractor).
• Also mentioned is the fact that the data is probably limited to inpatient populations, which represent one extreme.
• The authors list the fact that all the data are from administrative data sets, meaning diagnoses are likely subject to occasional miscoding or inaccuracy, warranting a sensitivity analysis.
• The article doesn’t give a list of the countries involved; granted it would be very difficult to break the data down by country since each review provides a single estimate, but simply listing the countries is still useful information.

If you need help

If you need help and support now and you live in the UK or the Republic of Ireland, please call the Samaritans on 116 123.

If you live elsewhere, we recommend finding a local Crisis Centre on the IASP website.

We also highly recommend that you visit the Connecting with People: Staying Safe resource.

Links

Chesney, E., Goodwin, G. M., & Fazel, S. (2014). Risks of all‐cause and suicide mortality in mental disorders: a meta‐review. World Psychiatry, 13(2), 153-160.

Capuron, L., & Miller, A. H. (2011). Immune system to brain signaling: neuropsychopharmacological implications. Pharmacology & therapeutics, 130(2), 226-238.

Gehanno, J.-F., Rollin, L., & Darmoni, S. (2013). Is the coverage of Google Scholar enough to be used alone for systematic reviews. BMC medical informatics and decision making, 13(1), 7.

Giustini, D., & Boulos, M. N. K. (2013). Google Scholar is not enough to be used alone for systematic reviews. Online journal of public health informatics, 5(2), 214.

Harris, E. C., & Barraclough, B. (1998). Excess mortality of mental disorder. The British Journal of Psychiatry, 173(1), 11-53. [PubMed abstract]

Hoang, U., Stewart, R., & Goldacre, M. J. (2011). Mortality after hospital discharge for people with schizophrenia or bipolar disorder: retrospective study of linked English hospital episode statistics, 1999-2006. BMJ, 343.

Lozano, R., Naghavi, M., Foreman, K., Lim, S., Shibuya, K., Aboyans, V., Abraham, J., Adair, T., Aggarwal, R., & Ahn, S. Y. (2013). Global and regional mortality from 235 causes of death for 20 age groups in 1990 and 2010: a systematic analysis for the Global Burden of Disease Study 2010 (PDF). The Lancet, 380(9859), 2095-2128.

Najt, P., Fusar-Poli, P., & Brambilla, P. (2011). Co-occurring mental and substance abuse disorders: A review on the potential predictors and clinical outcomes. Psychiatry Research, 186(2), 159-164. [PubMed abstract]

Shariff, S. Z., Bejaimal, S. A., Sontrop, J. M., Iansavichus, A. V., Haynes, R. B., Weir, M. A., & Garg, A. X. (2013). Retrieving clinical evidence: a comparison of PubMed and Google Scholar for quick clinical searches. Journal of medical Internet research, 15(8).

Whiteford, H. A., Degenhardt, L., Rehm, J., Baxter, A. J., Ferrari, A. J., Erskine, H. E., Charlson, F. J., Norman, R. E., Flaxman, A. D., & Johns, N. (2013). Global burden of disease attributable to mental and substance use disorders: findings from the Global Burden of Disease Study 2010. The Lancet, 382(9904), 1575-1586. [PubMed abstract]