Theories of addiction.

Addiction is currently de ned as a behaviour over which an individual has impaired control with harmful consequences (Cottler, 1993; Rounsaville et al., 1993). Thus, individuals who recognize that the behaviour is harming them or those whom they care about  nd themselves unable to stop engaging in the behaviour when they try to do so (Heather, 1998). The severity of the medical, psychological and social harm that can be caused by addiction, together with the fact that it violates the individual’s freedom of choice, means that it is appropriate to consider it to be a form of psychiatric disorder: a disorder of motivation. The main challenges for theories of addiction are to explain how this happens both at an individual and a societal level, and what mechanisms and societal changes underlie prevention and recovery. Addiction typically involves initial exposure to a stimulus followed by behaviours seeking to repeat the experience. After a number of repetitions of the behaviour–stimulus sequence, the addiction becomes established. The character and severity of the addiction may change over time, and it may be punctuated by attempts by the sufferer to abstain or regain control. In some cases, sufferers will achieve recovery for a sustained period or even permanently. There are inevitable questions about what constitutes a theory in the  eld of addiction. The Oxford English Dictionary de nes a theory as ‘a scheme or system of ideas or statements held as an explanation or account of a group of facts or phenomena’. Much of what is proposed as theory may be considered by some to be too speci c or descriptive to warrant the epithet. Often the terms ‘theory’ and ‘model’ are used interchangeably. Strictly speaking, a ‘model’ is better construed as a coherent representation of key elements of a structure or system and is thus more descriptive than explanatory, but in practice the dividing line between ‘model’ and ‘theory’ is  ne and open to differing interpretations. This article adopts a fairly pragmatic approach, including models and theories which attempt to make some kind of statement about mechanisms and processes which go beyond the immediate observation. A search of Medline and the Science and Social Science Citation Indexes using the keywords ‘theory’ or ‘model’ together with ‘addiction’, ‘dependence’, ‘alcohol’, ‘drug’ or ‘nicotine’ yielded a host of articles. Reviews of theories of addiction can also be found in Glass (1991) and more recently in a special issue of Addiction focusing on alcohol craving but also addressing craving more generally (Lowman et al., 2000). Examining the theories uncovered by the literature search, a simple classi cation system involving  ve groups suggested itself. The  rst group involves theories that attempt to provide broad insights into the conceptualization of addiction. Thus addiction may be construed in terms of biological, social or psychological processes, or some combination of these. Table 1 gives previously published examples of such approaches. For example, Orford (1992) has proposed a general conceptualization of addiction from a particular disciplinary perspective (see also Orford, 2001). Heather (1998) similarly proposes a broad theoretical framework. McCusker & Gettings (1997) focus more speci cally on cognitive mechanisms (and see McCusker, 2001). Papers by Drummond