How does alcohol affect serotonin in the brain?

This is an incredibly broad question. The basic theory is that many drugs force there to be an excess of serotonin in the synapse of a neuron, by either stopping the re-uptake of it (antidepressants) or by other complex actions (amphetamines). The addicts nervous system begins to take note of this and not produce/release as much serotonin, this leads to a state of low level endogenous serotonin production, thus leading to withdrawal and craving. By taking said drug again, the patient is able to feel normal again. It should be noted that this is an extremely simple explanation of this, and that addiction is a VERY complex topic.. Dr. Dan