Soda Got You Down? Not So Fast!

A new research study (not yet published) sponsored by the NIH suggests that drinking sweetened beverages is associated with an increased risk of depression. Boasting a total sample size of 263,925 individuals ranging from 50 to 71 years old, the study began in 1995-1996 when researchers evaluated consumption of soda, tea, fruit punch and coffee. About 10 years later, the same individuals were asked whether or not they had been diagnosed with depression since 2000 (so beginning about 5 years after the study began). The findings:

  • 11,311 depression diagnoses were made (so about 4.3% of the entire study population)
  • Those who drank more than 4 cans of soda per day were 30% more likely to develop depression than those who drank no soda.
  • Fruit punch gets an even worse rating: 38% more likely to develop depression when compared to those that did not drink fruit punch.
  • Oh finally….some good news: individuals who drank four cups of coffee per day were 10% less likely to develop depression when compared to non-coffee drinkers.

Hold your horses! Is this relevant, or just another piece of literature that news media needs to get some ratings? You guessed it….

Let’s start with re-interpreting the numbers. We first know that 4.3% of the study population developed diagnosed depression. Yet, the Centers for Disease Control and Prevention is providing an almost double estimate here, with 9.1% of adults meeting the criteria for major depression. Now, of course, this is assuming that both the CDC and the researchers of this study used the same criteria for depression, something that I cannot confirm since the study has yet to be published. So why the vast difference, especially since the sample sizes were relatively similar (263,925 vs. 235,067)? A question hopefully answered a little later in the post.

Moving on, heavy soda drinkers (more than 4 cans per day) were 30% more likely to develop depression when compared to non-soda drinkers. This 30% might seem a tad high, but really all this is saying is: those who drank more than 4 cans of soda per day were 1.3 times more likely to develop depression when compared to non-soda drinkers. While statistically significant (another assumption I’m making based on not actually having the article to read), this figure is largely unimpressive and for me, practically insignificant. Same goes for fruit punch….1.38 times more likely…get the picture? But the best part is yet to come!

For those avid coffee drinkers (4 cups of Joe per day), a 10% less chance to develop depression might seem great and all…..if only it were relevant. You mean to tell me that I am 0.9 times as likely to develop depression if I drink a whopping 4 cups per day? I better get on the coffee maker day and night then! (hint: sarcasm).

Should you stop or reduce soda intake? Sure…but not necessarily because you might get depressed. You should stop drinking soda because of the widely-accepted links between sugary drinks and obesity, diabetes etc. Stop drinking soda because each can contribute over 150 calories to your 2500 calorie diet (on average). Drink five of those and you’re at a third of your daily recommended intake.

So what may be wrong with this study? Below are some ideas, though unproven since I don’t have access to the study methods, data source, analysis etc.

  • While the study sample is similar to that of the CDC, the CDC samples it’s participants from across the country. Where did the participants for the soda study come from? Currently unknown. A difference in the proportion of diagnoses may come from the sampling techniques used in this study.
  • Is “1.3 times” really irrelevant? Not necessarily, though in this case, I’d assume so. Especially since:
  • Depression is extremely complex and is dependent on many complex relationships between the individual and his/her environment. Smoking, alcohol consumption, life events, chemical imbalances…all can lead to depression.
  • Drink 4 cups of coffee for a 10% decrease in the chance for depression? You’ve got to be kidding me! I’d rather avoid becoming anxious and dependent on coffee than drink 4 cups each and every day.

And before I end, I think it’s worth mentioning that this article is scheduled to be presented at the American Academy of Neurology’s annual meeting in March…about the same time Mayor Bloomberg’s ban on soda is set to take effect. And there you have it…that’s my take…what’s yours?

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3 Comments

  1. They may define depression differently than the CDC, but as long as they kept the same definition in the study population the number are significant.

    The differences are not that big, but he sample size is large enough to make a difference. The preliminary findings are large enough to encourage me to drink coffee than soda or fruit punch with sugar.

    • Bogdan

      Is 10% that large of a finding? Think of an OR of 1.1 versus an OR of 1….is that really significant? Even if statistically significant, does it make a difference in the real world?

    • Bogdan

      RE: sample size – the larger the sample size, the more likely one is to find a statistically significant difference. I’m dealing with that now for my thesis. I’d love to see what kind of variables they controlled for in this study….did they control for other confounders & possible interactions? I’m anxiously waiting for this to get published and give it a thorough read!

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