Melissa Raven writes:

Some statistics are very powerful, because they convey a shocking message that demands attention. They are often referred to as ‘killer statistics’.

Here is one, and in fact it is doubly a killer statistic: ‘Depression will be the second largest killer after heart disease by 2020’.

It is on the ‘Depression Facts and Stats’  webpage of Dr Bob Murray and Alicia Fortinberry’s Uplift Program.

It is also on an increasing number of other webpages – thousands of them.

And unfortunately it is wildly inaccurate, as killer statistics often are.

The reference cited by Murray & Fortinberry is ‘WHO report on mental illness released October 4, 2001’. Clearly what this refers to is the WHO’s ‘World Health Report 2001 – Mental Health: New Understanding, New Hope’.

But according to that report, depression will be the second largest cause of burden of disease (disability-adjusted life years [DALYs]), not mortality, by 2020:

By the year 2020, if current trends for demographic and epidemiological transition continue, the burden of depression will increase to 5.7% of the total burden of disease, becoming the second leading cause of DALYs lost. Worldwide it will be second only to ischaemic heart disease for DALYs lost for both sexes. (p. 30)

According to the WHO/World Bank Global Burden of Disease study (Murray & Lopez 1996), the 10 leading causes of death worldwide in 2020 will be:

1. ischaemic heart disease

2. cerebrovascular disease

3. chronic obstructive pulmonary disease

4. lower respiratory infections

5. trachea/bronchus/lung cancers

6. road traffic accidents

7. tuberculosis

8. stomach cancer

9. HIV

10. self-inflicted injuries

(Table 7.4, p. 362. Murray & Lopez actually presented three different projections, based on different scenarios, but the top 10 causes of death are similar in all three. Conveniently, Murray & Lopez’s table has been reproduced in Flint et al.’s (2007) ‘Trauma: Contemporary Principles and Therapy’ (p. 27, Table 8).)

Some fatal self-inflicted injuries would be partly attributable to depression, but by no means all. So depression will be nowhere near the second leading killer in 2020. Most people with depression do not die particularly young, so most of the burden of disease comes from years lived with disability, not from premature mortality.

I contacted Murray and Fortinberry about this problem weeks ago, and I was told on 15 February that the webpage was being changed ‘now’.

But the killer statistic is still there, as are other misleading claims. And even if it is eventually removed from the webpage, I predict that it will still be doing the rounds in 2020. Once these killer statistics are launched, they tend to have considerable longevity.

Another inaccurate statistic cropped up very publicly last year in Shadow Minister for Health & Ageing Peter Dutton’s mental health motion, which was passed in the House of Representatives in November.

It was also in Senator Concetta Fierravanti-Wells’ similarly worded motion in the Senate, and in Shadow Parliamentary Secretary for Primary Healthcare Andrew Southcott’s speech to Peter Dutton’s motion.

It is not about causes of death, but it is also a killer statistic: ‘mental illness afflicts more Australians than almost all other health disorders, only ranking behind cancer and heart disease in prevalence’.

Once again, burden of disease has been confused with something else, in this case prevalence. The reality is that mental illness ranks third (2003) or fourth (2013 projection) behind cancer and cardiovascular disease in terms of burden of disease (Begg et al. 2007, p. 125), not prevalence.

Now that this inaccurate statistic is enshrined in Hansard, it is sure to crop up repeatedly in the ongoing mental health debate, and few people will question it.

As Associate Professr Jon Jureidini and I pointed out last year, misleading killer statistics are all too common in the mental health field, as is resistance to retracting them. And they are usually taken at face value, particularly when uttered by experts.

Next time you read or hear a startling statistic about depression, or suicide, or mental illness, or mental health services, you would do well to stop and think, ‘Hang on, is this actually accurate?’.

• Melissa Raven is a psychiatric epidemiologist and policy analyst, Adjunct Lecturer, Discipline of Public Health, Flinders University and a member, of Healthy Skepticism.

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