A study released by the American Academy of Neurology Tuesday indicates that diet soda and other sweetened drinks are linked to an increased risk of depression. Coffee, on the other hand, was associated with lowering the risk of depression slightly.

The study will be presented at the 65th annual meeting of the American Academy of Neurology in March. The research was led by Honglei Chen, M.D., Ph.D., from the National Institute of Environmental Health Sciences in Research Triangle Park, N.C.

The study included 263,925 volunteers between the ages of 50 and 71. Researchers analyzed the amount of soda, fruit juices, tea, coffee and other sweetened drinks consumed in 1995 and 1996. Researchers then conducted a follow-up interview to determine how many participants were diagnosed with depression since 2000. Of the 263,925 participants, 11,311 were so diagnosed.

Chen, who is also the head of the Aging & Neuroepidemiology Group at NIEHS, said in a statement, “Sweetened beverages, coffee and tea are commonly consumed worldwide and have important physical — and may have important mental — health consequences.”

What the participants drank significantly affected their risk of being diagnosed with depression. According to the study, participants who drank more than four cans, or cups, of soda on a daily basis were 30 percent more likely to develop depression later on in life. Fruit punch had an even greater effect, with participants who drank four cans, or cups, a day 38 percent more likely to develop depression, according to the study.

The risk for developing depression was even higher for participants who consumed diet drinks such as diet soda or diet fruit juices, reports Bloomberg. But those who drank four cups or more of coffee daily were 10 percent less likely to develop depression.

The mechanism behind the increased risk for depression caused by sweetened drinks is unclear, and more studies are needed to truly understand the link between sweetened drinks and depression. According to Chen, “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. More research is needed to confirm these findings, and people with depression should continue to take depression medications prescribed by their doctors.”

Future studies could look at the individual components of the sweetened and diet drinks, such as artificial sweeteners or high-fructose corn syrup, to determine if these chemicals affect the risk of developing depression. In an email to Bloomberg, Chen said, “Although our results are preliminary, consumption of sweetened beverages should be reduced as they have been linked to other adverse health outcomes.”

Update: The American Beverage Association has issued a statement on the research linking sweetened drinks to depression, saying, "We may be in a new year, but there is nothing new about the ways our critics try to attack our industry.  This research is nothing more than an abstract – it has not been peer-reviewed, published or even, at the very least, presented at a scientific meeting.  Furthermore, neither this abstract nor the body of scientific evidence supports that drinking soda or other sweetened beverages causes depression.  Thus, promoting any alleged findings without supporting evidence is not only premature, but irresponsible."