The World Heath Organization reports that worldwide, an estimated 350 million people of all ages suffer from depression. According to the WHO, depression is the leading cause of disability around the globe and is a major contributor to the overall global burden of disease.

Ayahuasca, a psychotropic brew of two plants, the vine Banisteriopsis caapi and the leaves of the shrub Psychotria viridis, has been used for centuries in healing ceremonies in the Amazon. In the last few years ayahuasca has gained prominence on a global scale, with thousands traveling across the world to participate in indigenous ceremonies in South America, most notably in Peru. Concomitant with the growing popularity of ayahuasca as a tool for spiritual and physical healing is an increased scientific interest in understanding the biomedical underpinnings and treatment ramifications of this powerful medicine.

Recently, one of the most prestigious scientific journals, Nature, highlighted research conducted by a team of Brazilian from the University of São Paulo on the antidepressant effects of a single dose of ayahuasca on a group of six individuals suffering from major depression. In that study, researchers demonstrated that ayahuasca was able to alleviate symptoms of depression within hours of intake and that the antidepressant effects persisted for weeks afterward.

While that study was the first ever to clinically assess the effects of ayahuasca on patients with depression and had very promising results, the small number of volunteers (six people) only hinted at the incredible potential of the plant medicine as a treatment for depression and anxiety.

Now, new research by the same team has sought to address some of the limitations of the previous study by increasing the number of participants and including neuroimaging techniques to assess blood flow in the brain after exposure to ayahuasca.

Seventeen volunteers with recurrent major depression, who did not experience any therapeutic relief from their current antidepressant medications, were included in this latest study. Volunteers spent two weeks in an inpatient psychiatric clinic prior to the study without taking any medications or recreational drugs. None of the volunteers had ever used ayahuasca before nor had any experience with illicit drugs. At the time of the study, three volunteers were experiencing a mild depressive episode, thirteen a moderate episode, and one a severe episode.

Patients were given ayahuasca in individual sessions in a dimly lit room with a comfortable reclining chair. Importantly, as the researchers wanted to assess the pharmacological aspects of ayahuasca and not the ceremonial/ritual aspect of an ayahuasca experience, no ceremonial music or singing was included in the sessions. Vomiting was the only adverse effect recorded, with almost half the participants having vomited. However, none of the participants considered vomiting to be uncomfortable and deemed their overall ayahuasca experience as pleasant.

Various standard clinical questionnaires were used to assess depressive symptoms in the patients 10 minutes before the ayahuasca session, multiple times during the session, and up to three weeks after the experience. As previously reported, the antidepressant effects of ayahuasca were rapid, significantly reducing depressive symptoms in all patients within the first few hours of intake and were sustained over three weeks, which marked the end of the study.

Neuroimaging of the brains of the participants eight hours after ingesting ayahuasca revealed increased blood flow in areas of the brain whose diminished activation is usually associated with depression and increased activation is commonly associated with antidepressant effects.

The researchers attribute the antidepressant effects of ayahuasca to DMT, the principal psychoactive ingredient in ayahuasca, as it is an activator of serotonin receptors in the central and peripheral nervous systems. In other studies, DMT, psilocybin and LSD have been associated with increases in positive mood in healthy volunteers and in reducing anxiety and stress related to life-threatening diseases.

One of the key characteristics of depression is being stuck in negative thought patterns and constant overthinking of situations and life events. A special set of brain regions, known as the default mode network, exhibits increased activity in depressed patients and is associated with these negative thought patterns. Ayahuasca has been shown to reduce the activity of the default mode network and this reduced activity could also explain the antidepressant effects of ayahuasca observed in the present study. The researchers note that ayahuasca and other psychedelics change one’s self-perception, which “may reduce excessive attention to repetitive and pathological thoughts.”

Because the current study was not randomized or double-blind and lacked a control group, the authors could not conclude that the observed antidepressant effects were unequivocally due to ayahuasca intake. Furthermore, the authors state, “The controlled clinical setting in which the experiments took place is different from the typical ritual context of ayahuasca consumption, which may impact the generalizability of our findings.”

However, we may not have to wait much longer for an updated and more rigorous study on ayahuasca and depression. In a comment to the journal Nature, Draulio de Araujo, neuroscientist and co-author of the current study noted that he and his team hope to finish a randomized, double-blind, placebo-controlled study of ayahuasca and depression of a planned 80 patients by the end of this year.

Nevertheless, the results we have thus far are promising and suggestive of ayahuasca being a viable, well tolerated, fast-acting and long-lasting treatment for major depression and anxiety.