With long-term heavy alcohol use, there is an affect on the production of a chemical called GABA in the brain. The brain likes to keep in balance, so produces more glutamate, which has excitatory effects on brain activity. Suddenly removing the alcohol takes away the depressive effects of GABA, leaving the glumate to have an unchallenged effect, leading to the brain sometimes going haywire, including seizures and death in the worst situations.
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