SCTI

Addiction is any repeated behavior, substance-related or not, in which a person feels compelled to persist, regardless of its negative impact on his life and the lives of others. Addiction can also be called as substance dependence, which is a chronic, relapsing disease, affecting the brain's reward, motivation, and related systems. People struggling with addiction are unable to control their actions or make rational decisions about their behavior, even in the face of negative consequences. Compounds and experiences with addictive potential activate the brain's reward circuitry. These triggers are also called reinforcers because the pleasurable feeling we get from them makes us more likely to engage in them again and again. Both alcohol and illicit drugs are powerful reinforcers and cause the release of the neurotransmitter dopamine in the brain's reward system.

Repeated activation by these compounds changes the brain's reward system structurally and chemically and produces behaviours like bingeing, increasing usage and symptoms of withdrawal when the drugs are taken away.

Addiction involves:
Compulsive engagement with the behavior
Preoccupation with it
Impaired control over the behavior
Persistence or relapse, despite evidence of harm
Dissatisfaction, irritability or intense craving, if the substance is not immediately available.
Compulsion, impaired control, persistence, irritability, relapse and craving these are the hallmarks of addiction. Not all harmful compulsions are addictions, though, an obsessive-compulsive, for example, also has impaired control and persists in a ritualized and psychologically debilitating behavior such as, say, repeated hand washing. The difference is that he has no craving for it and, unlike the addict, he gets no kick out of his compulsion. Addiction is a process based in altered functioning of the reward and motivation systems of the brain. It can manifest in many ways, but historically addictions fall under two categories:
Substance-Related Addictions
Behavioral or Process Addictions

Substance Related Addictions
This kind of substance includes dependence on any of the following:
Tobacco
Alcohol
Opium
Cannabis
Heroin
Ice
Street drugs
Prescription drugs

Behavioral or Process Addictions
Although less well studied, many behaviors appear to have reinforcing properties, and may involve excesses related to:
Gambling
Food
Sex
Internet
Video Games
Work

Multiple Addictions and Co-morbid Factors
Science shows that substance and behavioral addictions can occur within the same individual and that multiple variants of substance or process addiction can be expressed at the same time. Thus, people can have multiple addictions with each addiction being active to differing degrees of severity. Additionally, depression and anxiety frequently accompany addiction as co-morbid factors.