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AAN study summary relies on speculation about diet and depression in older adults

Diet shown to reduce stroke risk may also reduce risk of depression

Our Review Summary

senior man eating dinnerThe release focuses on a forthcoming, preliminary study that will be presented at a conference in April. The release reports that people who closely follow the so-called “DASH diet” are less likely to report symptoms of depression than people who do not adhere to the DASH diet. However, there are a number of unanswered questions. For example, the study appears to have focused on older adults with an average age of 81 so it’s not clear whether the findings would be relevant for younger adults.

It’s also unclear whether depression leads to a change in dietary patterns. Common sense suggests lack of energy and motivation are negatively affected by depression and consequently may lead people to cook less frequently.  And it’s not clear how closely any of the groups being studied adhered to the DASH diet.

For further analysis of the study, the news release and resulting news coverage see our blog post.

 

Why This Matters

Clinical depression is a significant health issue, which can have profound ramifications for a patient’s well being and quality of life. There are a variety of treatment options available, but many of those options can be expensive or raise the possibility of adverse side effects. As a result, the idea that a lifestyle change, such as diet, could reduce the risk of depression is an attractive one. However, adopting a new diet is a big step for many people. It’s important for readers to understand the evidence behind the claims that a diet can significantly affect mental health risks. This release does some things well — such as noting at the very end that the study shows an association, not cause and effect. However, the release lacks key details that would allow people to clearly understand the underlying study.

Criteria

Does the news release adequately discuss the costs of the intervention?

Not Applicable

Costs are not discussed. However, the “treatment” at issue is not a drug or medical technology with clearly defined costs. Rather, the DASH diet focuses on an individual’s food choices. While there are cost constraints associated with any diet, and many people do not have easy access to the fruit and vegetables that are at the heart of the DASH diet, it would be challenging to address those issues in any meaningful way in the context of a news release like this one. That being the case, we’ll rate this as “not applicable.”

Does the news release adequately quantify the benefits of the treatment/test/product/procedure?

Not Satisfactory

The release states that “The odds of becoming depressed over time was 11 percent lower among the top group of DASH adherers versus the lowest group.”  Here the release is relying on relative risk reduction figures which are far less meaningful to patients than numbers that explain the absolute risk reduction.

We also are left wondering how closely the “top group of DASH adherers” followed the DASH diet? To what extent did that differ from the “lowest group”?

Does the news release adequately explain/quantify the harms of the intervention?

Satisfactory

The release does not address potential harms. However, there are few (if any) harms associated with adopting a well-balanced diet that is high in fruits and vegetables. While it is always wise to consult a physician before making significant lifestyle changes, we feel that this is not necessarily something that a news release needs to state explicitly. With that in mind, we give this a satisfactory rating.

Does the news release seem to grasp the quality of the evidence?

Not Satisfactory

One of the biggest problems with the release concerns lack of evidence concerning the DASH diet’s potential impact on depression.  Does depression lead to a change in dietary patterns? 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.

The release includes a caution at the end stating the study doesn’t prove cause and effect. That’s good, but we think the causal claim in the headline — “may also reduce depression” — will overshadow that message.

Does the news release commit disease-mongering?

Satisfactory

No disease mongering here.

Does the news release identify funding sources & disclose conflicts of interest?

Satisfactory

The release notes that the study was supported by the National Institute on Aging, which is good. However, conflicts of interest are not explicitly addressed. Given that only one of the researchers involved with the study was named, it is impossible for readers to determine if there are any conflicts of interest. For example, one can buy any number of DASH diet cookbooks online — are any study co-authors associated with those? Given the paucity of information in the release, it’s impossible to tell. (As noted above, we obtained a copy of the study abstract and didn’t see any obvious conflicts of interest — but the information isn’t readily available in the release.)

Does the news release compare the new approach with existing alternatives?

Not Satisfactory

One alternative raised in the release is the Mediterranean diet. But the release doesn’t describe the Mediterranean diet or quantify how adherence to that diet was associated with a decreased risk of depression symptoms. Other factors that can contribute to reduced risk of depression aren’t discussed.

Does the news release establish the availability of the treatment/test/product/procedure?

Not Satisfactory

The release refers repeatedly to the DASH diet. However, while the DASH diet has been around for years, many readers will likely never have heard of it. The release appears to assume that the DASH diet is common knowledge. While the DASH diet isn’t a secret, it’s not something you can assume readers are familiar with either. This could have been addressed by simply noting that the DASH diet has, well, been around for years. It could even have referred readers to a description of the plan on an NIH website.

Does the news release establish the true novelty of the approach?

Not Satisfactory

This is far from the first study to assess relationships between diet and depression. For example, a 2013 paper in Annals of Neurology that looked at (among other things) nine different studies involving the Mediterranean diet and depression. How does this forthcoming conference paper fit into that expansive body of work? It’s not clear. Based on the release, readers may think this is the first study to consider a link between diet and depression. To be clear, this research may well address novel research questions, but the release doesn’t make clear what those are — particularly in the context of previous work in the field.

Does the news release include unjustifiable, sensational language, including in the quotes of researchers?

Satisfactory

This is a tricky one. The release does one thing that we don’t like — and it does that thing more than once. The headline says “Diet…may also reduce risk of depression” (emphasis added). The first sentence says “People…may have lower rates of depression…” (emphasis added). In either instance, the release could just as easily have said “may not.” It begs the question of why the news release was issued at this point. However, we want to applaud two things the release does do. First, the release explicitly states that “the study does not prove that the DASH diet leads to a reduced risk of depression; it only shows an association.” That is such an important point to make, and we think that is great. Second, the release also quotes one of the researchers as saying “Future studies are now needed to confirm these results and to determine the best nutritional components of the DASH diet to prevent depression later in life and to best help people keep their brains healthy.” Again, this is an important point and we are very glad to see it addressed. All in all, we give it a satisfactory rating here.

Total Score: 4 of 9 Satisfactory

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