For at least two decades, thousands of Americans have been going to Peru, Ecuador, Colombia and Brazil to look for ayahuasca, a psychoactive brew traditionally used in sacred ceremonies in South America. Ayahuasca contains the psychedelic compound DMT, N-Dimethyltryptamine, and researchers are studying its effects on several conditions, including depression and addiction.

However, another sacred plant is quietly drawing Western seekers as well: huachuma, the Andean cactus better known as San Pedro. The plant contains mescaline, a psychoactive compound that alters perception and mood, sharpening the senses and amplifying feelings of empathy and connection.

Ceremonies and retreats are spreading across the U.S., Latin America and Europe into the thousands, as researchers take a fresh look at mescaline’s effects on depression, anxiety and addiction.

The Conversation asked Pardis Mahdavi, a medical anthropologist who conducts research on psychedelics, to explain what huachuma is, why seekers are turning to it, and what ethical questions come with its growing popularity.

Huachuma, whose Latin name is Echinopsis pachanoi, is a tall cactus that grows along the spine of the Andes, the mountain range on South America’s western side. Chemists know it as a natural source of mescaline, the same psychoactive compound found in peyote. While the chemistry of the two cacti is nearly identical, the experiences they offer, how they are served and why they are consumed are different.

People in the Andes have used huachuma to heal physical illnesses and treat mental health conditions such as depression and anxiety for a long time. Cactus remains found in a Peruvian cave suggest use stretching back perhaps 8,000 years. At some point before roughly 1300 B.C.E. the plant was carved in stone at Chavín de Huántar, a 3,000-year-old ceremonial complex in the northern highlands of Peru, cradled in the hands of a fanged deity.

In the healing traditions of northern Peru, curanderos, or traditional healers, usually train through years of apprenticeship,........

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