Page 34 - PhD GT

to account for their differences and Bradley (1990) has criticised this all inclusive position as being essentially a restatement of learning theory with little clinical utility.
In the substance dependence formulation, dependence on alcohol, cocaine, heroin or any other psychoactive substance is seen to be essentially the same phenomenon where dependence may transfer from one substance to another (Kosten et al. 1987). What distinguishes substance dependence from other behavioural dependencies like gambling and excessive sexual appetites is the way in which the substance alters the physiological substrate upon which it acts and thus its reinforcement potential is modified. Orford (1985) however, has argued that any arousal state can produce the subjective experience of craving and that the degree of arousal (the frequency and duration of arousal) experienced for example by gamblers may well result in such changes to the autonomic nervous system which are similar to the neuroadaptive state and have similar reinforcement potential. Since it is the reinforcement potential which is important in the present formulation of substance dependence, these commonalities may merit inclusion of a wider range of dependence conditions. Orford has further claimed that what distinguishes dependence from other behaviour is its functional autonomy: the action has become independent of whatever originally motivated it and ‘taken on a life of its own’. In the words of Logan, it has set up its own motivational system (Logan 1993 p. 299).
Chick (1980b) has argued that the nature of dependence needs further research for the purpose of clearly identifying whether there is a unidimensional syndrome and, if so, what its components might be. Empirical support for the connected ideas of a unidimensional condition that crosses substance boundaries and of a definition of dependence that does not require tolerance and withdrawal is suggested in a series of studies which examine the criteria for dependence and related disorders in the revised version of DSM-III (American Psychiatric Association 1987). When the ten items contained in these newly revised criteria were factor analysed for a group of 83 subjects abusing alcohol, sedatives, hallucinogens, stimulants, cannabis, cocaine and opiates, the dependence syndrome items were found to form a single factor for alcohol, opiates and cocaine, but not for the other substances (Kosten et al. 1987). It is predicted that removal of the items relating to tolerance and withdrawal will produce a set of dependence criteria which will form a unidimensional syndrome across substance boundaries.
A study of this question was part of a survey evaluating proposed options for DSM-IV (Carroll et al. 1994), when the investigators reported that their data provided little support for requiring tolerance and withdrawal for dependence and confirmed the view previously stated by Edwards et al. (1982) that tolerance could occur following a single administration of a drug and was
22