causes of sadness

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Aspartame, the artificial sweetener, may kill "friendly" gut flora associated with better moods. It also blocks the mood-moderating chemical serotonin (although effects were not noticed in people who had not had a history of a mood disorder). Together, these findings might help explain the results of a new NIH study: People who drank four or more cups daily of diet soda/diet iced tea had a 30 percent increased risk of depression compared to nondrinkers (more aspartame, higher risk). While the verdict's still out—correlation isn't causation—consider unsweetened coffee: at least four cups daily was linked with a 10 percent lower risk of depression.