Addiction in the brain is localized to one section known as the Limbic System, this is commonly referred to as “The Pleasure Center”. It is responsible for your natural reward systems you would get from normal healthy living. In the case of drug use, your limbic system is essentially being hijacked by the substance over throttling the release of Dopamine and securing a foothold in beginning or sustaining of an addictive tendency. Some drugs have a similar molecular structure to these neurotransmitters causing them to fit into the receptor that Dopamine would normally occupy.
After a habitual drug abuse the limbic system no longer naturally produces the same level of “pleasure chemicals” ie Dopamine, this unfortunately results in a lower quality of normal life and an addiction to whichever substances has caused the depletion. In a sense, the brain is now rewired to only seek out the substance to achieve that level of high. If the drug abuse has gone on for years it is difficult to get the body to produce the same level of natural chemical production once a decision has been made to quit the substance.
Specialized treatment is almost a necessity after quitting to ensure safe mental stability and to prevent a potential relapse into the arms of addiction. Quitting “Cold Turkey” unsupervised can present itself in the feelings of; anxiety, depression, insomnia, and thoughts of suicide. Addiction is one of the most difficult things any person could go through in their life, it ruins relationships, job opportunities, and long term goal planning.
Some might feel a level of hopelessness and despair in their journey to overcome the crippling weight that is the foothold that addiction has secured in their life but a thorough understanding of the mechanism of action along with qualified assistance will help better the circumstance substantially.