On 2015 Apr 24, Melissa Raven commented:

Inappropriate generalisation of mortality in mental disorders

This paper is one of an increasing number that inappropriately and dramatically generalise mortality estimates from samples of patients in secondary and very often tertiary treatment for serious chronic mental disorders (in many cases psychotic disorders) to the much broader population of people with potentially diagnosable mental disorders, which are usually much less severe and are associated with much lower mortality.

In this case, Mehta et al. have claimed that people with common mental disorders die 15-20 years earlier than people without such disorders. However, there is evidence of such a mortality gap only for people with chronic serious mental disorders (particularly psychosis) treated in secondary/tertiary settings. They have thereby grossly inflated the premature mortality associated with (and in effect attributable to) common mental disorders.

This statement is the problem:

'Interventions based on robust evidence with this approach have the potential to address a public health challenge that results in a 15–20 year premature mortality gap, in which 75% of people with common mental disorders receive no treatment,24,25 and which is increasingly sidelined as wellbeing policy ahead of the evidence.' (p. 3)

Mehta et al.'s reference 24, Ormel et al. (2008, p. 370), supports the claim that 75% of people with common mental disorders receive no treatment (in high-income countries). So far so good.

The source of the 15-20 year premature mortality gap statistic is neither of the two references cited. It is most likely Wahlbeck et al. (2011), which reported 'men with mental disorders still live 20 years less, and women 15 years less, than the general population' (p. 453). However, the sample was of people admitted to hospital for mental disorders. Wahlbeck et al. acknowledged that the patients were not representative of all people with mental disorders: 'Less serious non-hospitalised cases of mental disorders, possibly with a better life expectancy outcome, are not included' (p. 457).

The Wahlbeck et al. study was cited by Thornicroft and Docherty (2014) in support of their claim of a 15-20 year mortality gap, in their chapter in the UK Chief Medical Officer's Annual Report (Davies 2014) (the focus of Mehta et al.'s paper):

'men with mental disorders on average live 20 years less, and women 15 years less, than the general population' (p. 198)

Davies prominently and uncritically repeated Thornicroft & Docherty's claim (without citing any references) in her chapter 1, in her rationale for focusing on population mental health:

'There is an unacceptably large 'premature mortality gap': people with mental illness die on average 15–20 years earlier than those without, often from avoidable causes.' (p. 12)

A box below that claim unequivocally states that 'Mental illness … includes common mental disorder (including anxiety and depression), which affects nearly 1 in 4 of the population, and severe mental illness, such as psychosis, which is less common, affecting 0.5–1% of the population', leaving no doubt that the mortality claim applies to common mental disorders.

Mehta et al.'s reference 25 (Chang et al. 2010) did not report a mortality gap. However, another paper by several of the same authors (Chang et al. 2011) reported a somewhat smaller premature mortality gap (8 to14.6 years for men, and 9.8 to 17.5 years for women). [Clearly Mehta et al. have accidentally cited the wrong paper by Chang et al., making it harder to check the validity of their claim.] Again the sample was unrepresentative and biased towards more severe and more chronic cases. Chang et al. appropriately emphasised:

'Potential limitations include the secondary healthcare setting; this should present no problem for high penetrance disorders, such as schizophrenia and bipolar disorder, where most cases will have received secondary care input. However, findings for substance use disorders and depressive disorders should be viewed with circumspection since those appearing on a secondary care register are likely to be an unrepresentative (and probably more severe) subset of community cases. Ultimately, the findings for life expectancy should be taken as referring to people with these mental disorders who had made contact with secondary mental health services within the given time period and are not necessarily applicable to all cases in a given community.' (p. 5)

Mehta et al. (and Thornicroft & Docherty, and Davies) have ignored these authors' cautions. Their claim that people with common mental disorders die 15-20 years earlier than people without such disorders seriously misrepresents the evidence. It is ironic that Mehta et al.'s misleading sentence begins and ends with a focus on evidence, and occurs in a paper subtitled 'evidence-based priorities'. Similarly, it is ironic that this misleading claim is repeatedly emphasised in a report subtitled 'Investing in the Evidence'.

See also my PubMed Commons comment about Walker et al.'s (2015) systematic review and meta-analysis of mortality in mental disorders http://www.ncbi.nlm.nih.gov/pubmed/25671328, which similarly inappropriately generalises mortality from treatment samples of severe cases to the broader population of people with potentially diagnosable disorders, and my more detailed comment about it in JAMA Psychiatry (Raven 2015).

References

Chang CK, Hayes RD, Broadbent M, et al. (2010). All-cause mortality among people with serious mental illness (SMI), substance use disorders, and depressive disorders in southeast London: a cohort study. BMC Psychiatry, 10, 77. http://www.biomedcentral.com/1471-244X/10/77

Chang CK, Hayes RD, Perera G, et al. (2011). Life expectancy at birth for people with serious mental illness and other major disorders from a secondary mental health care case register in London. PLoS One, 6(5), e19590. http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0019590

Davies SC. (2014). Annual Report of the Chief Medical Officer 2013: Public Mental Health Priorities: Investing in the Evidence. London: Department of Health. https://www.gov.uk/government/publications/chief-medical-officer-cmo-annual-report-public-mental-health

Mehta N, Croudace T, & Davies SC. (2014). Public mental health: evidenced-based priorities. Lancet, 385(9976), 1472-1475. http://www.sciencedirect.com/science/article/pii/S0140673614614008

Ormel J, Petukhova M, Chatterji S, et al. (2008). Disability and treatment of specific mental and physical disorders across the world. British Journal of Psychiatry, 192(5), 368-375. http://bjp.rcpsych.org/content/192/5/368.long

Raven M. (2015). Inappropriate use of epidemiological data in analysis of mortality in mental disorders , JAMA Psychiatry. [comment re Walker et al. 2015) http://archpsyc.jamanetwork.com/article.aspx?articleid=2110027#tab10

Thornicroft G, & Docherty M. (2014). Chapter 12 Mind the gaps – treatment, funding, access and service provision. In S. C. Davies, Annual Report of the Chief Medical Officer 2013: Public Mental Health Priorities: Investing in the Evidence. London: Department of Health. 2014. https://www.gov.uk/government/publications/chief-medical-officer-cmo-annual-report-public-mental-health

Wahlbeck K, Westman J, Nordentoft M, Gissler M, Laursen TM. (2011). Outcomes of Nordic mental health systems: life expectancy of patients with mental disorders. British Journal of Psychiatry, 199(6), 453-458. http://bjp.rcpsych.org/content/199/6/453

Walker, ER, McGee R, & Druss BJ. (2015). Mortality in Mental Disorders and Global Disease Burden Implications: A Systematic Review and Meta-analysis. JAMA Psychiatry, 72(4), 334-341. http://archpsyc.jamanetwork.com/article.aspx?articleid=2110027

On 2015 Apr 24, Melissa Raven commented:

Inappropriate generalisation of mortality in mental disorders

This paper is one of an increasing number that inappropriately and dramatically generalise mortality estimates from samples of patients in secondary and very often tertiary treatment for serious chronic mental disorders (in many cases psychotic disorders) to the much broader population of people with potentially diagnosable mental disorders, which are usually much less severe and are associated with much lower mortality.

In this case, Mehta et al. have claimed that people with common mental disorders die 15-20 years earlier than people without such disorders. However, there is evidence of such a mortality gap only for people with chronic serious mental disorders (particularly psychosis) treated in secondary/tertiary settings. They have thereby grossly inflated the premature mortality associated with (and in effect attributable to) common mental disorders.

This statement is the problem:

'Interventions based on robust evidence with this approach have the potential to address a public health challenge that results in a 15–20 year premature mortality gap, in which 75% of people with common mental disorders receive no treatment,24,25 and which is increasingly sidelined as wellbeing policy ahead of the evidence.' (p. 3)

Mehta et al.'s reference 24, Ormel et al. (2008, p. 370), supports the claim that 75% of people with common mental disorders receive no treatment (in high-income countries). So far so good.

The source of the 15-20 year premature mortality gap statistic is neither of the two references cited. It is most likely Wahlbeck et al. (2011), which reported 'men with mental disorders still live 20 years less, and women 15 years less, than the general population' (p. 453). However, the sample was of people admitted to hospital for mental disorders. Wahlbeck et al. acknowledged that the patients were not representative of all people with mental disorders: 'Less serious non-hospitalised cases of mental disorders, possibly with a better life expectancy outcome, are not included' (p. 457).

The Wahlbeck et al. study was cited by Thornicroft and Docherty (2014) in support of their claim of a 15-20 year mortality gap, in their chapter in the UK Chief Medical Officer's Annual Report (Davies 2014) (the focus of Mehta et al.'s paper):

'men with mental disorders on average live 20 years less, and women 15 years less, than the general population' (p. 198)

Davies prominently and uncritically repeated Thornicroft & Docherty's claim (without citing any references) in her chapter 1, in her rationale for focusing on population mental health:

'There is an unacceptably large 'premature mortality gap': people with mental illness die on average 15–20 years earlier than those without, often from avoidable causes.' (p. 12)

A box below that claim unequivocally states that 'Mental illness … includes common mental disorder (including anxiety and depression), which affects nearly 1 in 4 of the population, and severe mental illness, such as psychosis, which is less common, affecting 0.5–1% of the population', leaving no doubt that the mortality claim applies to common mental disorders.

Mehta et al.'s reference 25 (Chang et al. 2010) did not report a mortality gap. However, another paper by several of the same authors (Chang et al. 2011) reported a somewhat smaller premature mortality gap (8 to14.6 years for men, and 9.8 to 17.5 years for women). [Clearly Mehta et al. have accidentally cited the wrong paper by Chang et al., making it harder to check the validity of their claim.] Again the sample was unrepresentative and biased towards more severe and more chronic cases. Chang et al. appropriately emphasised:

'Potential limitations include the secondary healthcare setting; this should present no problem for high penetrance disorders, such as schizophrenia and bipolar disorder, where most cases will have received secondary care input. However, findings for substance use disorders and depressive disorders should be viewed with circumspection since those appearing on a secondary care register are likely to be an unrepresentative (and probably more severe) subset of community cases. Ultimately, the findings for life expectancy should be taken as referring to people with these mental disorders who had made contact with secondary mental health services within the given time period and are not necessarily applicable to all cases in a given community.' (p. 5)

Mehta et al. (and Thornicroft & Docherty, and Davies) have ignored these authors' cautions. Their claim that people with common mental disorders die 15-20 years earlier than people without such disorders seriously misrepresents the evidence. It is ironic that Mehta et al.'s misleading sentence begins and ends with a focus on evidence, and occurs in a paper subtitled 'evidence-based priorities'. Similarly, it is ironic that this misleading claim is repeatedly emphasised in a report subtitled 'Investing in the Evidence'.

See also my PubMed Commons comment about Walker et al.'s (2015) systematic review and meta-analysis of mortality in mental disorders http://www.ncbi.nlm.nih.gov/pubmed/25671328, which similarly inappropriately generalises mortality from treatment samples of severe cases to the broader population of people with potentially diagnosable disorders, and my more detailed comment about it in JAMA Psychiatry (Raven 2015).

References

Chang CK, Hayes RD, Broadbent M, et al. (2010). All-cause mortality among people with serious mental illness (SMI), substance use disorders, and depressive disorders in southeast London: a cohort study. BMC Psychiatry, 10, 77. http://www.biomedcentral.com/1471-244X/10/77

Chang CK, Hayes RD, Perera G, et al. (2011). Life expectancy at birth for people with serious mental illness and other major disorders from a secondary mental health care case register in London. PLoS One, 6(5), e19590. http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0019590

Davies SC. (2014). Annual Report of the Chief Medical Officer 2013: Public Mental Health Priorities: Investing in the Evidence. London: Department of Health. https://www.gov.uk/government/publications/chief-medical-officer-cmo-annual-report-public-mental-health

Mehta N, Croudace T, & Davies SC. (2014). Public mental health: evidenced-based priorities. Lancet, 385(9976), 1472-1475. http://www.sciencedirect.com/science/article/pii/S0140673614614008

Ormel J, Petukhova M, Chatterji S, et al. (2008). Disability and treatment of specific mental and physical disorders across the world. British Journal of Psychiatry, 192(5), 368-375. http://bjp.rcpsych.org/content/192/5/368.long

Raven M. (2015). Inappropriate use of epidemiological data in analysis of mortality in mental disorders , JAMA Psychiatry. [comment re Walker et al. 2015) http://archpsyc.jamanetwork.com/article.aspx?articleid=2110027#tab10

Thornicroft G, & Docherty M. (2014). Chapter 12 Mind the gaps – treatment, funding, access and service provision. In S. C. Davies, Annual Report of the Chief Medical Officer 2013: Public Mental Health Priorities: Investing in the Evidence. London: Department of Health. 2014. https://www.gov.uk/government/publications/chief-medical-officer-cmo-annual-report-public-mental-health

Wahlbeck K, Westman J, Nordentoft M, Gissler M, Laursen TM. (2011). Outcomes of Nordic mental health systems: life expectancy of patients with mental disorders. British Journal of Psychiatry, 199(6), 453-458. http://bjp.rcpsych.org/content/199/6/453

Walker, ER, McGee R, & Druss BJ. (2015). Mortality in Mental Disorders and Global Disease Burden Implications: A Systematic Review and Meta-analysis. JAMA Psychiatry, 72(4), 334-341. http://archpsyc.jamanetwork.com/article.aspx?articleid=2110027