Please cite this article in press as: Halberstadt AL. Recent advances in the neuropsychopharmacology of serotonergic hallucinogens. Behav Brain Res (2014), http://dx. doi. org/10. 1016/j. bbr. 2014. 07. 016ARTICLE IN PRESSG Model BBR 9035 1-22 14 A. L. Halberstadt / Behavioural Brain Research xxx (2014) xxx-xxx members of other drug classes. Although it was recently reported that subjects administered high doses of the NMDA antagonist dextromethorphan under double-blind conditions identiﬁed it as a classical hallucinogen when they were asked to classify it pharma-cologically [435], there are major confounds associated with this study. First, Reissig et al. [435] acknowledged that most if not all of the study participants were expecting to receive psilocybin, and this may have inﬂuenced their response to dextromethorphan. Second, the subjects did not receive a hallucinogen as an active con-trol, so the study did not actually quantify the similarity between the effects of dextromethorphan and hallucinogens. It is also surprising that none of the subjects classiﬁed dextromethorphan as a dissociative anesthetic, since dextromethorphan is abused for its dissociative-like effects [436] and produces phencyclidine- and ketamine-like discriminative stimulus effects in rats [437,438]. Over the last decade, there has been renewed interest into the potential therapeutic uses for hallucinogens. Psilocybin can induce highly meaningful spiritual experiences [58], and some subjects have reported experiencing positive changes in mood and behav-ior that persist for many months [62]. It may be possible to exploit these effects therapeutically. 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