May is Mental Health Month and I’ve been getting questions about food’s effect on mental health, especially junk food.          One common question is , “ Do diet drinks  affect the brain and cause  depression?”         Yes.        In particular, the  artificial sweetener aspartame , found in diet soda,  is often blame d .         Aspartame has been studied for its potential effects on the nervous system, including mood . Unfortunately, two  studies have found that drinking aspartame-containing beverages increased risk of depression and one study also  worsened symptoms in those who already had diagnosed depression .       If aspartame causes depression, why do you say, "Everything in moderation?"           One  single can of diet soda doesn't cause depression. One teaspoon of  aspartame in your tea or coffee doesn't cause your existing depression  to worsen.  Even one can of soda a day in addition to one teaspoon of  aspartame add...