Does cannabis use predict poor outcome for heroin-dependent patients on maintenance treatment? Past findings and more evidence against

FRANÇAIS :
A partir des données collectées lors de 3 essais cliniques (d'une durée de 25-29 semaine et d'un suivi à 3,6 et 12 mois) concernant 408 polytoxicomanes admissibles en traitement de maintenance à la méthadone, les auteurs font une analyse rétrospective afin de déterminer si les résultats obtenus dans chaque essai sont reproductibles sur l'échantillon global. A l'entrée en traitement, les non-usagers de cannabis (test urinaire négatif) étaient 188, sur 220 patients usagers de cannabis, occasionnels ou fréquents, 15% étaient des usagers dépendants. La consommation de cannabis n'est pas corrélée à la rétention en traitement, ni à l'usage de cocaïne ou d'héroïne, ni à aucune des mesures faites au cours ou après le traitement.
ENGLISH :
Aims: To determine whether cannabinoid-positive urine specimens in heroin-dependent out-patients predict other drug use or impairments in psychosocial functioning, and whether such outcomes are better predicted by cannabis-use disorders than by cannabis use itself. Design: Retrospective analyses of three clinical trials: each included a behavioral intervention (contingency management) for cocaine or heroin use during methadone maintenance. Trials lasted 25-29 weeks; follow-up evaluations occurred 3, 6 and 12 months post-treatment. For the present analyses, data were pooled across trials where appropriate. Setting: Urban out-patient methadone clinic. Participants: Four hundred and eight polydrug abusers meeting methadone-maintenance criteria. Measurements: Participants were categorized as non-users, occasional users or frequent users of cannabis based on thrice-weekly qualitative urinalyses. Cannabis-use disorders were assessed with the Diagnostic Interview Schedule III-R. Outcome measures included proportion of cocaine- and opiate-positive urines and the Addiction Severity Index (at intake and follow-ups). Findings: Cannabis use was not associated with retention, use of cocaine or heroin, or any other outcome measure during or after treatment. Our analyses had a power of 0.95 to detect an r2 of 0.11 between cannabis use and heroin or cocaine use; the r2 we detected was less than 0.03 and non-significant. A previous finding, that cannabis use predicted lapse to heroin use in heroin- abstinent patients, did not replicate in our sample. However, cannabis-use disorders were associated weakly with psychosocial problems at post-treatment follow-up. Conclusions: Cannabinoid-positive urines need not be a major focus of clinical attention during treatment for opiate dependence, unless patients report symptoms of cannabis-use disorders.