Slightly more than 4 percent said they had. In general, people who consumed the most aspartame-sweetened diet beverages at the outset had a higher depression risk. Those who had downed at least four cans or cups of diet soda a day were 31 percent more likely to report depression than nondrinkers.
High intakes of artificially sweetened fruit punch and iced tea were linked to similar risks. Regular soda was as well, but the increased risk -- at 22 percent -- was lower than that linked to diet soda.
In contrast, people who had four or more cups of coffee a day had a roughly 10 percent lower risk of depression versus nondrinkers.
"This is an interesting study, and it's based on a large population," Redei said. She added that it's unusual for depression studies to focus on older adults, so it is good to see researchers look into the risk factors for later-life depression.
The problem is that many other factors might explain why diet drinks or coffee have a relationship with depression risk.
Two big ones are diabetes and obesity, Redei said. Both are common among older Americans, and both conditions are linked to higher odds of developing depression. People who are obese or have diabetes may favor diet drinks to help control their weight or blood sugar.
As for coffee, it may just be that healthy adults feel more free to drink a lot of it. "Older adults in poorer health may have been advised by their doctors to avoid caffeine," Redei said. And poorer physical health may translate into a higher depression risk.
Chen said his team statistically adjusted for many other factors, including weight and any reports of diabetes.
He noted, though, that overall lifestyle or other factors could still account for the findings. And it's not clear, Chen said, why diet drinks or coffee would have some direct effect on depression risk.
Until more is known, Redei cautioned older adults against lining up at Starbucks t
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