Deep in the Amazon basin, shaman prepare a natural tea called ayahuasca to bring its drinkers to hallucinogenic states of revelation. People come to the region from all over the world to take ayahuasca in order to make better contact with their emotions within or the spirits beyond--or simply to try the drug recreationally. But more recently scientists have been investigating ayahuasca as a treatment for psychological conditions such as PTSD and anxiety. Now a team of Brazilian researchers is testing the potion to treat depression, with promising preliminary results. They published their work recently in the journal Revista Brasileira de Psiquiatria (translation: Brazilian Review Of Psychiatry).

Ayahuasca is made from a jungle vine and shrub leaves and contains the chemical dimethyltryptamine, which makes it illegal in most countries (though many allow its consumption for religious purposes). Consuming the brew is notoriously hard on the system, resulting in excessive vomiting, disorientation, and occasionally death, but that doesn’t stop thousands of “ayahuasca tourists” from seeking it out every year. Though ayahuasca and the rituals surrounding it have been studied by social scientists and anthropologists, study of its medicinal properties has been limited to animal studies and a few with healthy volunteers. But researchers suspected that some of the compounds in ayahuasca change the concentration of mood-altering serotonin in the brain, as do commercial antidepressants.

In the study, the researchers gave doses of ayahuasca to six participants with depression for whom commercial antidepressants hadn’t been effective. As they sat in a dimly lit room, the researchers asked them questions from clinical questionnaires to track their symptoms. They found that the symptoms of depression decreased three hours after taking the ayahusaca (a typical trip lasts five hours) and they felt the positive effects for up to three weeks.

It’s important to note that there was no control group for this study, and there were very few participants, so the results should be taken with a grain of salt. However, the researchers are currently working on a study of similar design with many more participants that will track the symptoms for much longer after the participants take the ayahuasca.