More stable dispositions that influence behaviour across time and context, known as traits, are regarded as the components of a given person’s personality or character. The oft-quoted maxim by Oscar Wilde (1892), ‘I can resist everything but temptation’, implies (albeit paradoxically!) a disposition to gratification that is pertinent here. Is it valid or helpful to refer to an ‘addictive personality’, defined as a tendency to be unable to resist temptation as stated humorously by Lord Darlington, Oscar Wilde’s character in Lady Windermere‘s Fan? In a word, no! The reasoning underlying the notion of an addictive personality is circular, as evidence of diverse patterns of addictive behaviour is used to justify the disposition inferred from the behaviour. Moreover, at the neuronal level apparently diverse compulsive behaviours are eliciting similar outcomes, such as alterations in dopaminergic, glutamatergic or GABAergic transmission. In common with many intuitive theories, exceptions are ignored. For example, I recently saw a 32-year-old man with high levels of opiate dependence who had overcome his dependence on alcohol two years earlier. Remaining in the realm of the anecdote, I have also seen many individuals who had selectively overcome, or indeed relapsed with, addiction ‘A’, leaving addiction ‘B’ unaffected. Nonetheless, there are individual differences in addiction liability, which justifies this brief diversion into personality theory.

There is emerging consensus on the factorial structure of human personality as being the ‘Big Five’, or the Five-Factor Model (FFM): Neuroticism (N), Extraversion (E), Openness (O), Agreeableness (A) and Conscientiousness (C) (see Matthews et al., 2009, for a recent review). Combinations of these diverse dispositions no doubt could render an individual susceptible to developing an addictive disorder. For example, individuals ranked high on E and possibly low on C could be deemed susceptible because extroverts are more sensitive to the reward signals and, feeling less conscientious (low C), would display less perseverance in the face of temptation. Equally, however, individuals more disposed to anxiety (high N) could also be deemed vulnerable, because of sensitivity to punitive stimuli such as those that could be associated with withdrawal discomfort in the context of addiction. It appears plausible therefore that certain combinations of personality characteristics could well predispose individuals to more intensive pursuits of drug- or gambling-derived rewards. While there is no consensus on what constitutes an ‘addictive personality’ as a generic entity, at the individual or ideographic level personality factors such as impulsivity or emotional instability are surely relevant to formulation and therapeutic intervention.

Gray’s theory (e.g. 1991) proposed two major neurobehavioural systems, the behavioural activation system (BAS) and the behavioural inhibition system (BIS), which react to reward and threat signals respectively. More impulsive individuals tend to be stable extraverts, more sensitive to reward signals mediated by the BAS, based on forebrain structures such as the striatum. Due to the increased sensitivity reactivity of this system, highly impulsive people are more motivated by rewards than less impulsive people. This contrasts with the classic Eysenckian construct of extraversion, which assumed that extroverts (in effect impulsives) were characteristically underaroused neuronally and hence craved stimulation, novelty or the attention of others. On the other hand, highly anxious individuals, tending towards neurotic introversion, are more sensitive to threat signals. This generates testable predictions, for example that extraverts will learn optimally in rewarding conditions and introverts’ learning is better where punishment prevails (Pickering et al., 1995).

Clearly, the notion of a predisposition to reward sensitivity has implications for addiction susceptibility. Franken (2003), for example, found that a cohort of attendees at a drug treatment centre scored higher on standard measures of dimensions of the BAS compared with both attendees at an Alcohol Treatment Centre and controls recruited from the normal population. In the next section I shall briefly address enduring dysfunctional patterns in areas such as emotionality and impulsivity. These results suggest that disinhibition is a complex phenomenon that may be mediated either by BIS hypoactivity, BAS hyperactivity or even BIS hyperactivity. Further, impulsivity or disinhibition is influenced by the involvement of variables such as gender, personality, motivation, task and subject’s Anx state (p. 239). Lynam (2011) estimated that impulsivity or inhibitory failure feature in as many as 18 designated psychiatric disorders (DSM-IV; American Psychiatric Association, 1994). Inhibitory failure remains nonetheless a definitive component of addictive disorders and serves as an essential target for therapeutic intervention.

Personality disorders share high levels of coincidence with substance misuse disorders, at least among those who seeking treatment (Weaver et al., 2002). Here, a meaningful discussion of the merits or demerits of assigning diagnostic labels to people with enduring emotional behavioural and interpersonal difficulties is not possible. Following on from the discussion above about traits, a dimensional approach appears to offer more parsimony. Livesley et al. (1998) conducted a principal-component analysis that yielded four components they labelled the ‘the four As’. In order to achieve the mnemonic effect the terms are rather obscure, so I have clarified each term accordingly: Asthenic (emotional dysregulation), Anti-social (dissocial behaviour), Avoidance (inhibitedness) and Anankastic (compulsivity) (see Matthews et al., 2009, Chapter 11).

Whiteside and Lynam (2001) proposed that the FFM issues for personality traits reflect five relatively distinct pathways to impulsive behaviour.