Addiction: Addiction to drugs or behaviour is caused by associating the action with pleasure. When a gambling addict gambles: endorphins, adrenaline and serotonin is released to the brain. The brain ‘learns’ this, and then makes connections to seek this behaviour. This, in things like drugs, leads to tolerance; as more is needed to produce the levels one was initially experiencing.
It is important to note that physical chemical dependence is very much different from addiction. When someone who is dependant goes ‘cold-turkey’ they can experience withdrawal symptoms. These tend to be the exact opposite of the drugs affects. (i.e. depressants will cause seizures and spasms). The longer the half-life of the drug the longer the withdrawal stages. Withdrawal symptoms can include anything from depression, cravings, violent shaking and vomiting to death. It is not suggested an addict abruptly stop taking drugs, although withdrawal symtoms can be treated and subdued.