Put down that lemonade and step away from the orange squash because today's Metro carried a large front page warning: 'Fizzy drinks 'linked to depression'.
'And squash is worse'.
The article states:
"Fizzy drinks and fruit squashes are being linked to depression in a study involving more than 250,000 people."
"Downing four cans of sparkling drinks a day raised the risk of mental illness by 30 per cent, while the same amount of squash increased it by 38 per cent, researchers said."
"The danger was greatest for those who opted for diet products."
At this point it seems relevant to point out there isn't really anything in the article that supports a claim that fizzy drinks and squashes increase the likelihood of depression.
It could be argued the headline is therefore a little misleading.
What the Metro and some other outlets have jumped upon is a correlation within the research between fizzy and diet drink consumption and instances of depression in a large group of 50 to 71-year-olds in the US. Conversely, we are told there was a correlation between people within the sample who drank more coffee and lower instances of depression.
But stating categorically that "sparkling drinks...raised the risk of mental illness by 30 per cent" woefully overlooks a host of issues.
Firstly, it is all about correlation without so much as a cursory exploration of causation. Even then, why decide that fizzy drinks cause depression? Why not decide that people who are prone to depression tend to drink more fizzy drinks, or less coffee?
We aren't told about any other important lifestyle factors such as diet, education and employment which might influence both depression and the reasons why people drink the drinks they do.
For example, is a greater than average fondness for fizzy drinks indicative of higher than average consumption of convenience or fast food? Are people who drink fizzy drinks or turn to diet varieties more or less likely to be battling obesity? Are the obese more or less likely to be depressed? Is dieting a contributory factor? Or what about the reasons why some people feel the need to diet such as ill-health, or poor body image and self-confidence?
Or if the coffee drinkers are all grabbing coffees on their way to work, is it their coffee or their career that makes them less likely to suffer depression? Is coffee more synonymous with employment than fruit squashes? You may see more colleagues drinking coffee in meetings than lemon squash.
If employment levels differed is there any suggestion that being unemployed might be a factor in contributing towards depression?
Or, as anybody who's ever been into Starbucks will agree, a coffee isn't cheap.
Might coffee drinkers be wealthier than people who drink more fizzy drinks and fruit squash?
Could wealth or poverty be factors in triggering some of the instances of depression recorded by the research?
Are some of the people drinking fizzy drinks using it as a mixer for whisky at breakfast time? Did this breakfast of champions cost them their driving licence or lead to the break up of their marriage or the loss of their job? Did they keep the alcohol content of their fizzy drinks secret because they were ashamed of their dependence?
We aren't told.
These may sound like ridiculous objections - deliberately so - but the point is we just don't know anywhere near enough about these people's lives to determine why they may have suffered depression.
The research presents evidence for people who were aged 50 to 71 at the start of the 10-year study.
In that age group we might safely assume some have struggled with issues such as ill-health, retirement and concerns about pensions, cost of living and elderly care and maybe even the loss of a loved one, possibly their husband or wife. Maybe households that drank more sugary drinks, or had diets which incorporated above average amounts of fizzy drinks, had more widows or widowers in this age group. So would it have been bereavement or fizzy drinks that was the bigger contributing factor to the surviving partner's depression?
Those on diet drinks, or cutting out coffee, may have been responding to health issues - such as diabetes, obesity, liver or heart disease. Could those factors be relevant? Or might it be the fizzy drinks? Could be either. Could be neither. Could be a combination of the two.
How many of this ageing sample had suffered depression previously in their younger years? What if they had but it hadn't been diagnosed back in the 1950s or 1960s when some of the older participants were in their twenties?
Of course the considerable sample size takes care of some anomalies but it is naive to assume the only thing which really differentiates any of the people in this study was their choice of drinks.
In the Metro's article it falls to the British Soft Drinks Association to point out the obvious:
"However, the British Soft Drinks Association said the study failed to address other factors, such as family history, and more research was needed."
But that wouldn't have made for such an eye-catching headline.
Some outlets such as the BBC have run the story with a fair amount of caution about the link to depression, stating also that even the lead researcher behind the study has made clear more studies are needed.
The Daily Mail version of this story was illustrated with a nubile young lady drinking from a can, who was most definitely outside the 50 to 71-year age group quoted in the study. Still, a wrinkly with a can doesn't look so good on the sidebar of shame does it.
Posted by: En_croute | Jan 10, 2013 at 09:57