Fact or fiction?: The week in numbers

A sceptical look at the headlines in a world of fake news and polarised politics

Air pollution in London. Image credit: David Holt, Flickr

How many deaths are due to air pollution?

On Friday it was reported that global pollution kills 9 million people a year and threatens the survival of human societies.

The study was published in The Lancet — you can read it here.

It is should be noted that pollution is not the cause of death recorded on 9 million death certificates — this is an estimate arrived at using lots of different sets of data.

The study’s lead author, professor Philip Landrigan, explained in an email:

By tracking which people in these populations die of pollution-related diseases such as cardiovascular disease, stroke or lung cancer and by correlating the frequency of deaths due to each disease with the average level of pollution to which an individual is exposed, it becomes possible to establish an ‘exposure-response relationship’, in which a given level of pollution exposure is correlated with a given risk of disease. Put simply, higher levels of exposure result in more disease, and lower exposures in less disease, and this exposure-response relationship has been carefully measured for each pollution-related disease.

With big health reviews like this with attention-grabbing number of deaths, it’s always worth noting how heavyweight the study is — it’s a huge report with hundreds of references published in a well respected journal.

Is self-harming among teenage girls on the rise?

On Thursday it was reported that Self-harming was up by 70% among young teenage girls.

The study was published in the British Medical Journal — you can read it here.

The research points out that the numbers could be far higher, as it is thought that less than a quarter of self-harming young people report it to their GP.

The author also speculates that it’s possible that boys were less likely to go to a doctor, meaning the figure could be higher than reported among boys.

With stories like this that rely on self-reporting of medical issues, you need to keep in mind that people are not reliably honest about themselves, and ‘unreported’ figures on anything from crime rates to medical issues are, at best, estimates. The best you can hope for with ‘unreported’ figures is anonymous surveys with large samples.

Can magic mushrooms treat depression?

On Saturday it was reported that Magic mushrooms can ‘reset’ a depressed brain.

The study was conducted by Imperial College and published in Nature — you can read it here.

It is worth noting that the sample size was small — only 19 people were given the treatment. There was also no control group — a separate group with similar symptoms who were not given the treatment.

The authors acknowledge this: “this study is limited by its small sample size and absence of a control condition.”

This doesn’t mean the study should be discarded — it is the latest in a growing field of research looking at alternative treatments for depression.

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