Addictions can include, but are not limited to, drug abuse, exercise addiction, food addiction, computer addiction and gambling. Classic hallmarks of addiction include impaired control over substances or behavior, preoccupation with substance or behavior, continued use despite consequences, and denial. Habits and patterns associated with addiction are typically characterized by immediate gratification (short-term reward), coupled with delayed deleterious effects (long-term costs).
Physiological dependence occurs when the body has to adjust to the substance by incorporating the substance into its "normal" functioning. This state creates the conditions of tolerance and withdrawal. Tolerance is the process by which the body continually adapts to the substance and requires increasingly larger amounts to achieve the original effects. Withdrawal refers to physical and psychological symptoms experienced when reducing or discontinuing a substance that the body has become dependent on. Symptoms of withdrawal generally include but are not limited to anxiety, irritability, intense cravings for the substance, nausea, hallucinations, headaches, cold sweats, and tremors.
Substance dependence can be diagnosed with physiological dependence, evidence of tolerance or withdrawal, or without physiological dependence. DSM-IV substance dependencies include:
303.90 Alcohol dependence
304.00 Opioid dependence
304.10 Sedative, hypnotic, or anxiolytic dependence (including benzodiazepine dependence and barbiturate dependence)
304.20 Cocaine dependence
304.30 Cannabis dependence
304.40 Amphetamine dependence (or amphetamine-like)
304.50 Hallucinogen dependence
304.60 Inhalant dependence
304.80 Polysubstance dependence
304.90 Phencyclidine (or phencyclidine-like) dependence
304.90 Other (or unknown) substance dependence
305.10 Nicotine dependence
The term addiction is also sometimes applied to compulsions that are not substance-related, such as compulsive shopping, sex addiction/compulsive sex, overeating, problem gambling, exercise/sport and computer addiction. In these kinds of common usages, the term addiction is used to describe a recurring compulsion by an individual to engage in some specific activity, despite harmful consequences, as deemed by the user themselves to their individual health, mental state, or social life. There may be biological and psychological factors contributing to these addictions. Users may not be aware that their behavior is out of control and causing problems for themselves and others.
The word addiction is used in several different ways. One definition describes physical addiction. This is a biological state in which the body adapts to the presence of a drug so that drug no longer has the same effect; this is known as tolerance. Because of tolerance, there is a biological reaction when the drug is withdrawn. Another form of physical addiction is the phenomenon of overreaction by the brain to drugs (or to cues associated with the drugs). An alcoholic walking into a bar, for instance, will feel an extra pull to have a drink because of these cues.
However, most addictive behavior is not related to either physical tolerance or exposure to cues. People compulsively use drugs, gamble, or shop nearly always in reaction to being emotionally stressed, whether or not they have a physical addiction. Since these psychologically based addictions are not based on drug or brain effects, they can account for why people frequently switch addictive actions from one drug to a completely different kind of drug, or even to a non-drug behavior. The focus of the addiction isn't what matters; it's the need to take action under certain kinds of stress. Treating this kind of addiction requires an understanding of how it works psychologically.
When referring to any kind of addiction, it is important to recognize that its cause is not simply a search for pleasure and that addiction has nothing to do with one's morality or strength of character. Experts debate whether addiction is a "disease" or a true mental illness, whether drug dependence and addiction mean the same thing, and many other aspects of addiction. Such debates are not likely to be resolved soon. But the lack of resolution does not preclude effective treatment. Help is available!
Resources: Psychology Today, Wikipedia