Thursday, June 24, 2010

Diet, Depression, and Anxiety

This post will focus on a single paper, published in March 2010 in the American Journal of Psychiatry: Association of Western and Traditional Diets With Depression and Anxiety in Women. (Thank you to Dr. Hale for pointing out the study). In the introduction, the authors make note that depression and anxiety are highly prevalent with other chronic dietary-related illnesses such as cardiovascular disease, obesity, and type 2 diabetes. At the same time, psychiatry lacks evidence-based prevention and treatment strategies based on dietary modification. That may be for the best, considering what has happened with obesity and type II diabetes over the past 30 years, but that is, in part, why I'm trying to get the information out, blog-wise.

So - the study! Well, these researchers in Australia hijacked an ongoing study, called the "Geelong Osteoporosis Study." Thousands of intrepid women were randomly picked from compulsory voting rolls, and all told, 1046 women ages 20-93 were followed for roughly 10 years for the diet and depression part. Each participant filled out yearly questionnaires about her diet. (Problem number one - imagine I gave you a questionnaire about your usual consumption of 74 foods, 6 alcoholic beverages, and the type of bread, dairy products, and fat spreads you used? How accurate could it be? The researchers say the "comprehensive food frequency questionnaire" was a validated instrument, but one must keep limitations in mind.)

Then, all participants were given a SCID (that's a standard structured clinical interview used to diagnose psychiatric disorders in research), and they looked for current diagnoses of major depressive disorder, dysthymia (a low-grade, ongoing depression), and anxiety disorders. Also, a wide variety of statistical analysis tools were used to account for so-called "covariates" such as socioeconomic status, physical activity, alcohol consumption, and smoking. (Problem number two - which is the major problem with any observational study - one can never really account for all the covariates. For example, people who drink moderate amounts of wine have less heart disease. Wine could be a factor in that. Or perhaps people who drink wine happen to exercise more. Or maybe people who drink wine also have magical hearts. We really don't know. If you take a group of people and force-feed some a glass of wine or two a day, and then tell another group to abstain, then see if there is a difference in heart disease between the two groups, then you have a prospective trial, and that's not the kind of data we're talking about with the current study I'm examining, which is an observational study. We end up with associations and correlations with such studies, which are interesting, but could be meaningless. Tom Naughton brings up this issue and the 2010 US dietary guidelines in this blog post. Don't click that link if you have extremely delicate sensibilities.) The researchers weighed and measured the height of all the participants also.

Results! Everyone's diet was analyzed and segregated into three basic groups - traditional, Western, and modern. Traditional diets were comprised of vegetables, fruit, beef, lamb, fish, and whole grain foods. A Western pattern was associated with meat pies (Australian fast food), processed meats, pizza, chips (I seriously do not know if they mean french fries or potato chips here - Australian readers, help me out!), hamburgers, white bread, sugar, flavored milk drinks, and beer. The "modern" diet consisted of fruits, salads, fish, tofu, beans, nuts, yogurt, and red wine (in other words, the people who read the news reports on all the observational studies out there...).

And the punch line? A traditional dietary pattern "was associated with a lower likelihood of depressive and anxiety disorders."

Traditional fruit, veggie, lamb, beef, fish and whole grain eaters had a 25% lower risk for major chronic disease (cardiovascular disease and cancer) after 10 years. They had 35% reduced odds for having major depression or dysthymia, and 32% reduced odds for anxiety disorders. The "Western" (junk) and "modern" (bean, fish, wine, and tofu) eaters fared about the same, but the Western eaters were slightly more depressed.

So there you have it! Beans and tofu and meat pies are correlated with depression and anxiety! Well, the authors of the study are pretty fair about the limitations of their design in the discussion. The do mention another study and how high-fat, high-sugar diets caused decreased hippocampal BDNF in animals, and that diets high in refined carbohydrates are associated with more inflammation. They also made note that a Mediterranean-style diet (which would roughly correspond to the traditional and modern diets) tends to decrease inflammatory markers.

I wonder what the data would look like without the whole grain eaters? Also, full fat dairy versus low fat dairy. Why do researchers never present the really interesting stuff to a paleolithic diet-inspired psychiatrist?

(A sobering thought is that I may be the only paleolithic-diet inspired psychiatrist).

5 comments:

  1. Emily,

    Not Australian - I'm a Kiwi (some would say that is a good thing). A chip in these parts refers to French Fries (or Freedom Fries if you still call them that!). However, our chips (from fish & chip shops) are generally a lot thicker than French Fries.

    Confusingly, we also call our potato chips 'chips' as well (though we sometimes call them crisps also).

    On the anxiety front, have you read much that links teh likes of gluten intolerance, IBS, etc, with higher anxiety states? I have seen a little bit and clinical experience suggests this to be true.

    There is a great series of articles that are freely available titled "Stress and the Gastrointestinal Tract" - a couple here:

    http://ajpgi.physiology.org/cgi/reprint/280/4/G519

    http://ajpgi.physiology.org/cgi/reprint/280/2/G173

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  2. What's a meat pie? As I child, my mother served us commercial chicken pot pies: chicken bits, a few veggies, and God-knows-what-else cooked in a pie crust for about an hour in the oven.

    Once the researchers collect to dietary data, they can always go back and devise various diet scores and look for associations. I'm sure they could come up with a paleo diet score and run the numbers, if they were interested.

    Same for a low-carb diet score and Mediterranean diet score.

    Seems to me that there's a lot of overlap between these eating styles. I'm not too impressed witht the strength of this study.

    "Data dredging" comes to mind.

    -Steve

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  3. Jamie - I would say in my practice, almost everyone with IBS has concomitant anxiety. But of course, that isn't exactly a random sampling. Also, "Generalized Anxiety Disorder" is characterized by general worry and physical symptoms (headaches, muscle aches, GI distress), so almost anyone with IBS who walks into my office and is a "worrier" can meet criteria for GAD. I'll definitely look at those links. There's also a strong link between bipolar disorder and the inflammatory bowel diseases.

    Steve - No, it's not the world's greatest study. But largish dietary trials and data are few and far between in psychiatry, so I take what I can get. There is a vegetarian study (the seventh day adventist study), a Japanese study, and a gluten-free diet study in celiac patients (brand new - June 10 2010). I'll go over those in the next post.

    Interestingly, the researchers also came up with an "overall diet quality score" based upon Australian food guidelines (similar to the USDA guidelines) - the closer the diet came to the guidelines, the higher the diet quality score. There was no additional protection from a "high quality" diet against depression and anxiety, once one adjusted the data for age, socioeconomic status, education, physical activity, smoking, and alcohol consumption. Only the "traditional" pattern stood out as protective.

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  4. Hi from Australia

    Here, chips are the hot ones: wedges of potato deep fried in oil. Maybe a bit thicker (usually) than your fries.

    Meat pies are pies of pasty containing meat and gravy. Eat with tomato sauce on top. Good convenient meal (eat with one hand) for sports events. Not sure the % of meat or the quality of meat in them, suspect its the reject meat!

    Just found your blog from a post on Mark's Daily Apple: trying out a primal diet. Fascinated by some of your blogs about the psych and other metabolic effects and I thik I will be a regular reader. Thanks Emily!

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  5. Hey I was wondering if you knew any ways to develop self confidence? I have become very self conscious over that last year... (Im a 20 year old male) and I need to fix this :(. Any ideas?

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