In the study, people who drank sweetened beverages -- including regular and diet sodas, fruit punch, and sweetened iced tea -- had a higher risk for depression.
Researchers say the findings suggest that cutting down on sweetened drinks or replacing them entirely with non-sweetened beverages may help lower depression risk.
But an expert who reviewed the findings says it failed to convince him that drinking sweetened beverages raises depression risk.
“There is much more evidence that people who are depressed crave sweet things than there is to suggest that sweetened beverages cause depression,” says neurologist Kenneth M. Heilman, MD.
Heilman is a professor of neurology at the University of Florida College of Medicine in Gainesville.
The study included close to 264,000 people over the age of 50 enrolled in an AARP diet and health study.
When they entered the study, the participants were asked about their beverage-drinking habits as part of a detailed dietary survey. About 10 years later they were asked if they had been diagnosed with depression over the previous decade.
The analysis revealed that people who drank more than four cans or cups of diet soda a day had about a 30% higher risk of developing depression over the follow-up period than those who drank none. Those who drank regular soda had a 22% higher risk.
Coffee drinking, however, was associated with a 10% reduction in depression risk.
Drinking diet sweetened-beverages appeared to be associated with a slightly higher depression risk overall than drinking sugar-sweetened beverages.
More Research Needed, Expert Skeptical
The researchers noted that more research is needed to confirm the findings. They warn that people with depression should continue to take all medications prescribed by their doctors.
“While our findings are preliminary, and the underlying biological mechanisms are not known, they are intriguing and consistent with a small but growing body of evidence suggesting that artificially sweetened beverages may be associated with poor health outcomes,” says researcher Honglei Chen, MD, PhD, of the National Institutes of Health in Research Triangle Park, N.C.