Psychedelic experience sources of some psychedelic drugs such as ayahuasca and mescaline-containing cacti are sometimes referred to as "plant teachers". Similarly, in a follow-up to the psilocybin and mysticism study at Johns Hopkins, researchers observed that psilocybin: "occasions personally and spiritually significant mystical experiences that predict long-term changes in behaviors, attitudes and values". Psychedelic experience includes the full range of mystical or religious experiential phenomena. Two scientific studies have concluded that psilocybin (a typical psychedelic compound that occurs naturally in psilocybin mushrooms) reliably triggers mystical-type experiences. The more recent study at Johns Hopkins University identified mystical experiences by means of several questionnaires
Mescaline and activates the serotonin 5-HT receptor with a high affinity. How activating the 5-HT receptor leads to psychedelia is still unknown, but it is likely that somehow it involves excitation of neurons in the prefrontal cortex. Mescaline is also known to bind to and activate the serotonin 5-HT receptor. Difluoromescaline and trifluoromescaline are more potent than mescaline, as is its amphetamine homologue trimethoxyamphetamine. In the United States, mescaline was made illegal in 1970 by the Comprehensive Drug Abuse Prevention and Control Act, categorized as a Schedule I hallucinogen. The drug was prohibited internationally by the 1971 Convention on Psychotropic Substances.