•  cocaine;
  • heroin;
  • polydrug use;
  • alcohol;
  • treatment outcomes

I was interested to read the paper by Staiger and colleagues [1]. Although we persist in referring to drug and alcohol problems by reference to single substances, this can be misleading. It is now more than 10 years since I wrote an editorial in this journal about something that has long been known by all who work with people with substance use disorders: ‘Few drug takers confine themselves to using a single substance. Cigarettes and alcohol often go together. Heroin users may also take drugs such as cocaine and benzodiazepines, and heavy drinkers often also use illicit drugs. Virtually all heroin addicts are also cigarette smokers’ [2]. The point of my editorial was that although the reality of multiple substance use is well known, it is seldom given the attention that it deserves. The reasons for this are many. Not the least of these is that matters become complicated when multiple substances are considered. For instance, if someone regularly uses two (or more) drugs, do they have one or two (or more) drug problems? If they are dependent upon two (or more drugs), do they have a more severe dependence problem than if they took only one drug? Is severity of dependence upon each drug additive? Or interactive? Or synergistic?

‘Our favourite drug’, alcohol, is widely used and widely misused. Within the extended menu of substances used by drug takers, alcohol has a special place and deserves greater attention than it generally receives. Staiger et al. draw our attention back to the misuse of alcohol by drug addicts and to the dearth of studies about how alcohol misuse may interact with other drug problems. Heavy drinking among patients in methadone programmes has been recognized as a problem since such programmes were established [3]. Heavy drinking among drug misusers is also associated with serious health risks. Hepatitis C infection is common among injection drug users (IDUs), and infected people who drink heavily are at greatly increased risk of serious liver disease. Drug overdose is one of the most frequent causes of death among drug misusers, and heavy drinking among opiate misusers greatly increases the risk of overdose: many so-called heroin overdoses should be attributed more accurately to the combined use of alcohol with opiates [4].

Heavy drinking was relatively common among dependent heroin users in the National Treatment Outcome Research Study (NTORS): approximately a quarter were drinking heavily at treatment intake, and the same proportion continued to drink heavily throughout the 5-year follow-up [5]. Although some problematic drinkers reduced their frequency and quantity of drinking, many made little change in their drinking behaviour; even with the reductions in quantity of alcohol among the problematic drinkers, typical daily amounts of alcohol at follow-up were between 10 and 19 units (approximately half a bottle of spirits) [6]. The interrelationship between drinking and drug use remains poorly understood. Staiger et al. report several studies showing that alcohol use increases relapse to drug use. Our own research suggested that changes in heroin use and drinking outcomes may be largely independent, although heroin misusers who had poor drinking outcomes were more likely to also be using cocaine, amphetamines and benzodiazepines [6].

One interesting but little-discussed aspect of the substance use behaviours of drug addicts is that although many are heavy drinkers, a relatively high proportion are abstinent from alcohol. More than a third of the NTORS sample had not used alcohol at all during the 3 months before treatment, and the proportion who were alcohol-abstainers remained constant throughout the 5-year study [5]. This abstinence rate is much higher than for the general population.

It is not only the drinking behaviour of heroin addicts that is neglected. There is surprisingly little interest in the broader issue of multiple substance misuse. Although there are problems with a substance-specific approach to drug use disorders, it is important to remember that different drugs have different attractions for different users. For example, the relatively high rates of alcohol abstinence among heroin addicts may not be found among other groups of drug misusers. A common pattern of multiple substance misuse involves the concurrent use of cocaine and alcohol. The combined use of alcohol and cocaine produces increased and prolonged euphoria compared to either substance on its own [7], and for some cocaine users the concurrent use of alcohol is an integral part of their pattern of drug-taking. This effect may also be influenced by the type of cocaine being used. Cocaine powder users report more frequent heavy drinking than crack users, and whereas cocaine powder users tended to use cocaine and alcohol concurrently, crack users tended to use alcohol at the end of crack-using sessions [8, 9].

Drug users with concurrent polydrug use problems may require special consideration and treatment planning. Alcohol use and, in particular, excessive drinking, is often neglected in the treatment of drug users. Drug users and clinical staff may focus either deliberately or unintentionally upon what is perceived to be the main illicit problem drug and under-rate the use of other substances. The extent and severity of heavy drinking among drug misusers points to the need to develop programmes and interventions that are designed specifically to tackle alcohol-related problems in this client group.

Declaration of interests



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