Addiction

Addiction describes the dependency of a person on a substance or an activity that has become a habit through more or less repeated use. Drug addiction describes the habitual, excessive use of toxic substances which are harmful to the person or to society and which cause a state of psychological and/or physical dependency. The commonest addictions involve relatively non-toxic substances (caffeine), toxic substances (nicotine) or hard drugs (heroin). Addiction to an activity is probably due to release of endorphins in the circulating blood associated with enjoying the activity, which can generally be differentiated from obsessive compulsive behaviour.