NDARC Technical Report No. 208 (2004)
Cocaine use among treatment entrants for heroin dependence in NSW became common during the ‘heroin drought’ of 2001. Recent studies demonstrated that heroin users who also used cocaine were a more ‘at risk’ group at treatment entry (Williamson et al, 2003) and showed poorer short term outcomes (Williamson et al, 2004). Overall, they displayed higher current levels of social dysfunction, drug use, needle-risk taking behaviour and criminality. It was unknown whether these patterns would persist past the initial stages of treatment, and what effect differing patterns of cocaine use over time would have on outcome.
The current study was conducted as part of the Australian Treatment Outcome Study (ATOS). ATOS is the first large scale longitudinal study of treatment outcome for heroin dependence to be conducted in Australia. The current study was conducted twelve months post treatment entry. The aims of the current study were: to determine the effect of cocaine use on outcomes of treatment for heroin dependence twelve months post-treatment entry; to examine the relationship between cocaine use and dysfunction among heroin users; and to examine the effects of persistence of cocaine use over follow up on outcomes.
The prevalence of cocaine use in the sample had decreased from 39% at baseline to 10% at twelve months. Frequency of use had also decreased: only ten percent of current users reported using cocaine daily at twelve months, compared to a quarter at baseline. Those who were enrolling in treatment at baseline interview were significantly less likely to report recent cocaine use at twelve months, while current cocaine users at twelve months had spent significantly fewer days in treatment.
Baseline cocaine users were significantly less likely to be retained in their index maintenance pharmacotherapy at follow up, but no differences were noted in relation to retention in index detoxification or residential rehabilitation programs. Baseline cocaine users also spent significantly fewer days in treatment over the follow up period. Persistent cocaine use over the study period was associated with treatment instability, with more persistent cocaine use associated with commencing a greater number of treatment episodes.
At baseline, three and twelve months CU consistently displayed a higher level of social dysfunction. At twelve months they remained more likely to report gaining the majority of their income from criminal activity and homelessness was more prevalent amongst this group. The same pattern of results was also observed for current cocaine users at twelve months. The more interview points at which cocaine use was reported, the higher the prevalence of homelessness (12% cocaine use at all points vs 1% no cocaine use).
Baseline cocaine use was a significant predictor of continuing heroin use at twelve months (49% vs 37%), and of failure to attain abstinence from heroin over the entire follow up period. Moreover, more persistent cocaine use was associated with higher rates of heroin use at follow up, and with failure to maintain heroin abstinence since baseline. Almost twice the proportion of current cocaine users as non-current users reported heroin use at follow up (78% vs 37%). Baseline cocaine use was not a predictor of more extensive polydrug use at twelve months. Persistent cocaine use over the follow up period, however, predicted higher levels of polydrug use at follow up, as did current cocaine use.
Baseline and current cocaine use were predictors of needle sharing at twelve months, and the more points cocaine use was reported at, the greater the prevalence of needle sharing. Injection-related health problems were also predicted by baseline and current cocaine use and increased with increasing persistence of cocaine use (eg 72% of those who used at all points vs 21 % of non-cocaine users).
By twelve months, baseline cocaine use no longer predicted higher levels of criminal activity. It did, however, predict incarceration over the follow up period. Having reported cocaine use at more interview points was an independent predictor of greater criminal involvement at follow up, and the more points at which cocaine use was reported, the greater the likelihood that the subject had been imprisoned since baseline. Current cocaine users at twelve months were also significantly more likely to have recently engaged in criminal activity (45% vs 22%).
Physical and mental health
Current cocaine users reported poorer general physical health than non-users at twelve months. Baseline cocaine use was not associated with poorer general health outcomes at this time, although baseline cocaine users were more likely to have recently used ambulance or general practitioner services. Injection-related health problems at twelve months were predicted by baseline and current cocaine use and persistence of cocaine use was an independent predictor of injection-related health problems. The general mental health of the sample was not differentiated by baseline cocaine use or persistence of use. At twelve month follow up however, current cocaine users reported poorer general mental well being.
The prevalence and frequency of cocaine use had declined significantly in the sample by twelve months. Despite decreased availability of the drug, however, 10% continued to use cocaine. Any cocaine use over the study period was associated with decreased stability of treatment and poorer outcomes on virtually all outcome measures. Persistent cocaine use over the study period, however, appeared particularly detrimental in relation to almost all outcome measures. Cocaine use among clients should evidentially be a cause for concern amongst treatment providers. Such use is linked to a wide variety of harms and high-risk behaviours, and importantly, to continuing poorer treatment outcome.
Citation: A. Williamson, S. Darke, J. Ross & M. Teesson (2004), Cocaine use and treatment outcomes for heroin dependence: 12 month outcomes, Sydney: National Drug and Alcohol Research Centre.