Background and aims: Cannabis use is frequent among individuals with cocaine use disorder. Despite recent non-controlled studies advocating a therapeutic role of smoked cannabis, there is a paucity of evidence-based data on potential therapeutic and cognitive side-effects of this association.
Methods: We examined 63 cocaine-addicted subjects who used cannabis more than 50 times in lifetime (COC + CAN), 24 cocaine-addicted patients who use cannabis less than 50 times (COC), and 36 controls (CON). Participants were evaluated with an extensive battery of neurocognitive tests after two weeks of supervised detoxification in an inpatient treatment program. Patients were followed up in one, three, and six months after discharge.
Results: Both groups of patients performed worse than CON on working memory, processing speed, inhibitory control, mental flexibility, and decision making. COC + CAN performed worse than COC on speed processing, inhibitory control and sustained attention, while COC performed worse than COC + CAN on mental flexibility. Concomitant cannabis use did not decrease relapses to cocaine use after one, three and six months. Among COC + CAN, earlier cocaine and cannabis use, and impaired executive functioning were predictive of relapse on cocaine after six months.
Conclusion: Our results did not support the recommendation of smoked cannabis as a safe therapeutic approach for cocaine-addicted patients due to significant negative cognitive side-effects and absence of efficacy. Further studies investigating frontal brain morphology, neuromaturation, and prescription of the non-psychoactive constituent of cannabis sativa cannabidiol among cocaine-addicted patients who use cannabis are warranted.
Keywords: Cannabis; Cocaine; Cognition; Executive functions; Polydrug.
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