People who drank more than 4 sodas (sugar-sweetened or diet) per day were 30% more likely to be diagnosed with depression than those who consumed none. Those who drank 4 cans of fruit punch per day (sugar-sweetened or diet) were 38% more likely to become depressed. Consuming diet versions of soda and fruit punches was associated with a greater risk for depression than consuming versions sweetened with regular sugar. Interestingly, those who drank 4 cups of coffee per day were 10% less likely to develop depression than those who drank none.
National Institutes of Health, January 2013