Diet Soda Addiction
Some research indicates that the artificial sweeteners in diet soda, like aspartame, may have addictive properties. The brain may become conditioned to crave sweetness, leading to increased consumption of diet soda over time.
Sugar Addiction Link
The constant stimulation of sweetness without calories can trick the brain into developing a dependency on the taste, making it difficult to cut back.
Conclusion
Though it contains no sugar, diet soda may lead to addiction-like behaviors due to the artificial sweeteners used.