Conceptualizing addiction has been a matter of great debate for decades. Redish et al. put forth a “unified framework” for addiction, but it is only unified at one reductionist level of analysis (i.e., biological) relating to just one aspect (i.e., decision-making). It is clear that conceptualization of addiction has implications for several groups of people (e.g., addicts, their families, researchers, practitioners, policy-makers, etc.). Obviously, the needs of these groups may not be equally well served by certain models, and in some cases there will be absolute incompatibility. Whether Redish et al.'s “unified framework” will help specific stakeholders (such as policy-makers, practitioners, and the addicts themselves) is highly debatable. Implicit within the claims made by any particular group or individual will be assumptions about what levels and types of risk are acceptable in the pursuit of pleasure, and, more simply, which kinds of pleasure are acceptable and which are not. Any unified framework for the conceptualization of addiction must allow for the bottom-up development and integration of theory by each of these groups – that is, it must be flexible, accountable, integrative, and reflexive.

It is also important to acknowledge that the meanings of addiction, as the word is understood in both daily and in academic usage, are contextual and socially constructed (Howitt Reference Howitt1991; Irvine Reference Irvine1995; Truan Reference Truan1993). Researchers must ask whether the term “addiction” actually identifies a distinct phenomenon – something beyond problematic behaviour – whether socially constructed or physiologically based. There is clearly a case for a complex systems model of addiction. “Complex” for obvious reasons, and “systems” after Davies (Reference Davies1992), who argues that alternative explanations for excessive behaviour require “the development of a ‘system’ within which drug use is conceived of as an activity carried out for positive reasons, by people who make individual decisions about their substance use, and who may take drugs competently as well as incompetently” (p. 163). Gambino and Shaffer (Reference Gambino and Shaffer1979) have emphasized the difficulties of re-integrating research and practice in the area of addiction. On the basis of Polkinghorne's (Reference Polkinghorne and Kvale1993) observations on the nature of such divisions, a more flexible theoretical approach, such as the complex systems model, ought to go some way toward bridging the epistemological gap.

The complex systems model corresponds well to the biopsychosocial approach to addiction (e.g., Griffiths Reference Griffiths2005; Marlatt et al. Reference Marlatt, Baer, Donovan and Kivlahan1988; McMurran Reference McMurran1994). It may also be considered to be a descendant of previous multi-factorial approaches to the addiction process (e.g., Wanberg & Horn Reference Wanberg and Horn1983; Zinberg Reference Zinberg1984). Obviously, from the perspective of the complex systems model, it is possible to consider the interaction of both the common and the unique elements of any specific individual's situation. This includes psychological, physiological, social, and cultural factors that may be particular to any individual. It also allows for consideration of the pharmacological properties of specific substances, or the reinforcing properties of certain kinds of behaviour such as gambling. It is important, therefore, to point out that this is not a return to citing the property of “addictiveness” as located within particular substances (or within particular activities). However, it is necessary to be aware of effects that may be common to certain kinds of substances or activities, but not to others.

Neurological and pharmacological work on addiction (despite some discrepancies and disagreements) allows us to remove the emphasis on substance use (and thus lose some of the awkward discourse associated with it) and include behavioural activities, as well as to acknowledge the powerful behavioural dimension of substance addictions (see Sunderwirth & Milkman Reference Sunderwirth and Milkman1991). For this, Redish and colleagues should be commended because their unified approach allows activities like problem gambling to be considered bona fide addictions. Any activity that is rewarding may thus be seen as potentially addictive, but only those activities with a social disapproval of their attached “risk” are viewed as addictions, rather than habits, in the current climate. This is a strong argument for a greater understanding of the addiction concept.

In a biopsychosocial complex systems model of addiction, the process of addiction is dynamic, in which the addict, while responding to needs for arousal or satiation, and learned patterns of behaviour, as well as reacting to the environment, still has recourse to a decision-making process with regard to the modification of their physiological state. A number of biological, psychological, and socio-cultural factors will determine the nature of this process.

The biological effects of any particular behaviour or drug (i.e., the subjectively experienced intensity, and the stimulating and/or sedating effect of that behaviour or drug) may have a strong relationship with other biological factors (e.g., opponent-process adaptation to that effect), as well as with the psychological factors (e.g., the subjectively experienced craving for that behaviour or drug) and the social factors (e.g., prompting of the craving through peer behaviour), which interact together during the addictive process. The nature of those reinforcing effects will, of course, be essentially similar to, and yet crucially distinct from, those of other activities and substances.

Most of my own research has concentrated on behavioural addiction (i.e., non-chemical addictions), particularly gambling addiction but also addictions to videogame playing, Internet use, exercise, and sex (for summaries of these, see Allegre et al. Reference Allegre, Souville, Therme and Griffiths2006; Griffiths Reference Griffiths2004; Reference Griffiths and Plante2006; Reference Griffiths, Willoughby and Wood2008; Widyanto & Griffiths Reference Widyanto, Griffiths and Gackenbach2006). Redish et al. have a very narrow approach when talking about gambling as an addiction, and their “unified framework” also needs to include these other types of behavioural addictions. Gambling addiction is a multifaceted rather than unitary phenomenon, and the decision-making approach (while useful on some levels) is very limited. Consequently, as with addiction more generally, many factors may come into play in various ways and at different levels of analysis (e.g., biological, social, or psychological). Theories may be complementary rather than mutually exclusive, which suggests that limitations of individual theories might be overcome through the combination of ideas from different perspectives. It is evident that problem gambling (specifically) and addiction (more generally) is a biopsychosocial process (Griffiths Reference Griffiths2005; Griffiths & Delfabbro Reference Griffiths and Delfabbro2001) and that a narrow focus upon one theoretical perspective in the explanation of gambling and addictive behaviour cannot be justified.