January 9/Washington/National Cancer Institute -- While depression most likely has a myriad of possible causes, a new study, authored by Honglei Chen, MD, PhD, of the National Institutes of Health (NIH) in Research Triangle Park in North Carolina and a member of the American Academy of Neurology (AAN), might just help to put a feather in the cap of NYC Mayor Michael Bloomberg and his recent initiative to limit the size of sugary beverages that can be purchased for consumption.

Bloomberg, in an effort to curb increasing obesity rates in his city, got his proposal to ban the sale of large sugary beverages in restaurants, at street vendors and movie theaters approved by the New York City Board of Health back in September. His motives were to help slim waistlines in his city. Now, as it turns out, perhaps his initiative might also lead to elevating the levity of his constituency.

According to Chen’s research, a suggestion has been made that drinking sweetened beverages like sodas, fruit punches and teas may have a negative effect, not only on the waistline but also on one's peace of mind. This possible link to depression had a noted increase in those who consumed diet beverages. Chen released his study today and will be presenting his findings at the American Academy of Neurology’s 65th Annual Meeting in San Diego in March of this year.

“Sweetened beverages, coffee and tea are commonly consumed worldwide and have important physical -- and may have important mental -- health consequences,” said Chen,

Researchers started this study in 1995, observing a total of 263,925 participants all between the ages of 50 and 71. From 1995-96, Chen’s team evaluated the consumption of beverages such as soda, tea, fruit punch and coffee among the study participants. After a 10-year hiatus, the researchers then conducted interviews with each of the participants, asking whether they had been diagnosed with depression since the year 2000. Of the initial 263,925 members of the study group, 11,311 depression diagnoses had been made.

Specifically, what the team noted was that individuals who had consumed more than four cans or cups of soda per day were at a 30% higher risk of developing depression when compared to individuals in the study who had consumed no soda. Additionally, artificially sweetened fruit juices, consumed at the 4 or more marker, accounted for a 38% higher likelihood of depression over those who did not drink sweetened beverages. The risk of developing depression appeared greater for those individuals that imbibed diet sodas, fruit juices and teas, as compared to having just consumed the regular forms of those beverages.

On the transverse side of the study, individuals who enjoyed four cups of coffee per day were approximately 10% less likely to develop depression than those who drank no coffee at all.

Chen’s contention for this outcome is that due to coffee’s large amount of caffeine, perhaps it is the elevated levels of this brain stimulant that help to stave off depression.

This study, according to Chen, is one of the first studies conducted that looked to establish a link between sweetened beverages and depression. However, the connection is not explained and it is still unknown exactly how the drinks may be tied to mental health. A theory, however, claims that the sweet beverages tied to diabetes and obesity may be the reason some participants eventually developed depression.

“Although our results are preliminary, consumption of sweetened beverages should be reduced as they have been linked to other adverse health outcomes,” Chen said.

The team did not examine specific chemicals in the beverages, such as artificial sweeteners, to determine which ingredients in the beverages might lead to the eventual diagnosis of depression in the respondents.

Gaynor Bussell of the British Dietetic Association was quick to point out to the BBC that, as the results are based on U.S. respondents, the team’s findings might not necessarily apply to other populations.

Bussell also went on to say, “Sweeteners used to be called ‘artificial’ sweeteners and unfortunately the term ‘artificial’ has evoked suspicion. As a result, sweeteners have been very widely tested and reviewed for safety and the ones on the market have an excellent safety track record.”

These sweeteners include aspartame, saccharin, acesulfame potassium (K), cyclamate and sucralose. Each of them are virtually free of calories and are beneficial as they do not affect blood glucose levels. Their use in a wide range of products allows individuals to enjoy sugar-free, reduced sugar and low calorie foods and beverages.

Bussell is confident that this study was a “one-off” and did not mean sweeteners caused depression. “For a start, people who suffer from depression may latch on to the idea that it is their sweetened beverages that caused it and so add bias to their reporting of past intake, especially as ‘soda’ in the US is demonized even more than in the UK. Also, it may be that drinking ‘diet’ drinks is a marker for obesity or diabetes which in themselves can cause depression.”

“Non-calorific sweeteners can play a useful role in the diets of those trying to lose weight and diabetics and it is certainly not advocated that people should replace their diet sodas with more coffee,” Bussell continued.

“Our research suggests that cutting out or down on sweetened diet drinks or replacing them with unsweetened coffee may naturally help lower your depression risk,” Chen concluded. “More research is needed to confirm these findings, and people with depression should continue to take depression medications prescribed by their doctors.”

The study was supported by the National Institutes of Health, the National Institute of Environmental Health Sciences and the National Cancer Institute.