The study researchers analyzed information from more than 263,900 U.S. adults ages 50 to 71 who answered questions about their beverage consumption between the years 1995 and 1996. About 10 years later (from 2004 to 2006), the same people were asked if a doctor had diagnosed them with depression since the year 2000.

People who regularly drank four or more cans of any type of soda a day were 30 percent more likely to have received a diagnosis of depression than people who did not drink soda. The risk of depression was especially high for people who drank diet soda — a 31 percent increased risk compared to a 22 percent increased risk for those who drank regular soda, the researchers said.

Those who drank four or more cans of diet fruit drinks were 51 percent more likely to be diagnosed with depression compared to those who did not drink diet fruit drinks.