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Keywords:

  • Alcohol misuse;
  • drug dependence;
  • illicit drug use;
  • longitudinal studies;
  • outcomes studies;
  • recovery;
  • relapse;
  • residential drug treatment;
  • substitution

Abstract

Aims

Despite recognition of the harms related to alcohol misuse and its potential to interfere substantially with sustained recovery from drug dependency, research evaluating drug treatment outcomes has not addressed the issue comprehensively. It has been overlooked possibly because treatment research has been framed according to the primary drug of choice, rather than investigating the interactions between different combinations of drugs and/or alcohol use. This paper reports on a systematic review investigating whether concurrent alcohol use could impede recovery from illicit drug use in two potential ways: first, alcohol could become a substitute addiction and/or secondly, alcohol misuse post-treatment may place an individual at risk for relapse to their primary drug problem.

Method

A systematic search of four relevant databases was undertaken to identify peer-reviewed, quantitative drug treatment outcome studies that reported alcohol use pre-, post-treatment and follow-up.

Results

The search revealed 567 papers, of which 13 were assessed as fulfilling the key inclusion criteria.The review indicated inconsistent and therefore inconclusive support for the substitution hypothesis. However, the data revealed consistent support for the hypothesis that alcohol use increases relapse to drug use.

Conclusions

(i) The potential negative impact of alcohol misuse on drug treatment outcomes remains under-researched and overlooked; (ii) alcohol consumption post-drug treatment may increase the likelihood that an individual will relapse to their primary drug; (ii) existing evidence regarding the substitution hypothesis is inconclusive, although there was an indication that a subgroup of participants will be vulnerable to alcohol becoming the primary addiction instead of drugs. We argue that future drug treatment outcome studies need to include detailed analysis of the influence of alcohol use pre- and post-drug treatment.