Kevin Lomangino is the managing editor of HealthNewsReview.org. He tweets as @KLomangino.
News outlets are trumpeting headlines about a diet that can supposedly improve the public’s mental health. Specifically, the low-sodium DASH diet — recommended by some health authorities to reduce high blood pressure — is claimed by many recent news stories to also reduce the risk of depression:
Atlanta Journal-Constitution (AJC): What is the DASH diet? Heart-healthy diet may also reduce risk of depression
The coverage has some problems starting right in those headlines, all of which use language suggesting that the diet caused a reduction in depression risk.
Yet the study itself was observational in nature, meaning it can only detect associations between two things — not whether one thing caused another to happen.
A more accurate, appropriately cautious headline might read something along the lines of: “Study explores links between diet and depression risk.”
We offer tips for journalists who want to write better headlines about diet studies.
Perhaps a bigger problem with the coverage is this: The study supporting these claims hasn’t yet been published in a journal — something the AJC got wrong when it claimed the study was “published Sunday in the journal American Academy of Neurology.”
In fact, there is no published study, and an abstract of the research won’t even be presented until April. This means that these stories are all based entirely on a cursory American Academy of Neurology (AAN) news release about the study.
A news release is a promotional document that’s meant to be a starting point for a news story. It’s supposed to whet the appetite of journalists who want to dig deeper into an issue.
But in this case, there’s nothing else for reporters to dig into even if they wanted to. The data simply isn’t available.
The coverage from all three stories predictably features the same canned quotes from the lead researcher that are pulled directly from the news release.
They’re merely regurgitating the material that they’ve been spoon-fed by a public relations team.
None of the coverage I looked at featured any meaningful analysis of the study from an independent expert.
All of this raises questions about the decision-making that went into these stories:
Had they sought out an independent perspective, these stories might have reported context similar to what our expert reviewers — Matt Shipman and Yoni Freedhoff, MD — said in their systematic review of the AAN news release.
They warned that a study like this might appear to show that diet reduces the risk of depression, but that it can’t rule out an alternate scenario — that depression may cause some people to choose different, less-healthy diets than their counterparts who don’t have depression.
Fatigue and lack of motivation — both hallmarks of depression — may lead people to cook less frequently. Research also suggests that sugary foods lower cortisol levels more than other foods and consequently people with depression may choose them preferentially over a DASH style diet since they provide them with some therapeutic relief. And further, these are older adults (average age of 81). If they were to develop conditions that affected their energy, mobility, chronic pain, etc. this would also influence their dietary choices and impact these results.
If you are over 80 years of age, maybe a fruit- and vegetable-rich diet is simply a marker for being in relatively good health.
Maybe depression is something that degrades your diet in older age and these news stories have things backwards.
It’s difficult to say much with certainty because, again, there’s no study to substantiate any of this.
All the more reason to proceed slowly when it’s tempting to dash ahead of the evidence.