Yes, excessive Mountain Dew consumption is linked to disrupted cognitive ability, particularly memory loss and impaired brain function, though effects vary by quantity and individual factors.

Brominated Vegetable Oil (BVO): Historically used in Mountain Dew, BVO can accumulate in the brain and cause bromism, a neurological disorder characterized by memory loss, fatigue, headaches, and involuntary movements when consumed in large quantities (e.g., 2–8 liters daily). While major manufacturers have removed BVO from many products, some citrus-flavored sodas may still contain it or similar additives.
Sugar and Artificial Sweeteners: Regular consumption of sugary or diet sodas is associated with smaller brain volumes, poorer memory, and an increased risk of stroke and dementia. Studies indicate that daily diet soda drinkers are nearly three times more likely to develop dementia, while high sugar intake leads to brain atrophy and cognitive decline.
Mixed Effects of Ingredients: While caffeine in Mountain Dew may provide short-term improvements in alertness and focus, excessive intake can lead to sleep disruption, anxiety, and irritability, which indirectly harm cognitive performance. High sugar content also causes blood sugar spikes and crashes, leading to fluctuations in energy and attention.
For optimal cognitive health, health experts recommend limiting soda intake and choosing water or unsweetened beverages instead.