The word 'addiction' these days is used to refer to a chronic condition where there is an unhealthily powerful motivation to engage in a particular behaviour. This can be driven by many different factors - physiological, psychological, environmental and social. If we say that it is all about X, we miss V, W, Y and Z. So, some people think addicts are using drugs to escape from unhappy lives, feelings of anxiety and so on; many are. Some people think drugs become addictive because they alter the brain chemistry to create powerful urges; that is often true.