Dopamine is one of the major neurotransmitters involved in addiction. Drug addiction and alcohol abuse increases dopamine levels in the brain, creating increased feelings of pleasure. This might seem to be a good thing, but the increased levels have a long term adverse effect on brain chemistry, which leads to addiction.
When the level of dopamine in the brain remains constant, the body can experience the ordinary pleasures of life. However, when the brain is persistently subjected to artificially high levels of dopamine, due to drug or alcohol abuse, then the brain reduces the natural production of dopamine to maintain consistency. The brain thus becomes dependent on the presence of drugs or alcohol to maintain a semblance of normalcy. As soon as the drug or alcohol level decreases the individual experiences symptoms such as depression, tiredness or withdrawal. The only relief, therefore, is the intake of more and more levels of drugs or alcohol to maintain the equilibrium.
This all culminates in the addict’s constant craving and drive to obtain their chemical of choice.