Sure, diet soda pop is lower in sugar, but it does contain a number of substitute sweeteners. These substitute sweeteners have not been proven to be explicitly harmful, however previous studies only followed the results of ingesting small amounts. On top of that, there is also a direct link between diet soda and depression. In a study of 263,925 adults aged 51-70, individuals who drank soda were 30% more likely to be diagnosed with depression over a period of 10 years. The link was stronger for diet soda than regular soda. The main reason people switch to diet drinks is to cut back on calories in order to lose weight. Unfortunately, it doesn’t seem to work. In a study of 3,682 individuals from San Antonio, Texas, consumption of diet soda was associated with double the risk of becoming overweight or obese.