Hallucinogens are used in four broad ways: in traditional indigenous ceremonies, in supervised therapeutic settings, as recreational substances, and in sub-perceptual “microdoses.” Each context carries different intentions, doses, and risks, and the line between them is shifting as clinical research advances and legal frameworks evolve.
Traditional and Indigenous Ceremonial Use
Long before Western science took interest, indigenous peoples across the Americas used hallucinogenic plants as sacraments, medicines, and tools for spiritual communication. Peyote, a small cactus containing mescaline, was already in widespread ceremonial use at the time of Spanish rule in the Aztec Empire around 1520. The Spanish missionary Bernardino de Sahagún documented its religious and medicinal roles among the indigenous peoples of Mexico in 1569. During the American Civil War era, Native American groups continued using peyote for both ceremony and healing. The Kiowa people used it to treat flu, scarlet fever, tuberculosis, and venereal diseases. The Navajo have long used peyote rituals as powerful healing ceremonies for trauma and social disruption, viewing them as more effective than Western psychiatric approaches.
Ayahuasca, a brew containing DMT along with plant-based compounds that prevent the body from breaking down DMT before it reaches the brain, has been central to Amazonian spiritual traditions for centuries. Psilocybin mushrooms have similarly deep roots in Mesoamerican cultures. In all these traditions, the substance is not taken casually. Ceremonies typically involve a guide or shaman, structured rituals, dietary preparation, and a clear spiritual or healing intention. Indigenous communities also applied these plants topically or ingested them for physical ailments like burns, wounds, fever, rheumatism, and snakebites.
Supervised Therapeutic Use
The most rapidly growing use of hallucinogens today is in clinical therapy, where substances like psilocybin are administered under professional supervision to treat depression, anxiety, addiction, and PTSD. These sessions look nothing like recreational use. A patient typically takes a single measured dose in a calm, controlled room while one or two trained therapists sit nearby. The experience lasts several hours, and follow-up “integration” sessions help the patient process what they felt and experienced.
Clinical results have been striking. In a JAMA-published trial of single-dose psilocybin for major depressive disorder, 42% of participants who received psilocybin showed a sustained response in their depressive symptoms, compared to just 11% in the placebo group. About 25% achieved full remission, versus 9% on placebo. These results come from a single dose, not months of daily medication, which is part of what makes the approach so compelling to researchers.
The biological explanation centers on how these substances interact with serotonin signaling in the brain. Classical hallucinogens activate a specific type of serotonin receptor, which triggers signaling cascades that strengthen and grow new synaptic connections between brain cells. This process, called neuroplasticity, is thought to be the key mechanism behind lasting therapeutic benefits. Recent research published in Molecular Psychiatry has shown that psychedelics can even boost synaptic connectivity in neurons that don’t carry this receptor themselves, by activating it on neighboring input neurons. In other words, the brain-rewiring effects may be broader than initially understood.
MDMA, while technically not a classical hallucinogen, has been tested in a similar supervised model for PTSD. The FDA granted it breakthrough therapy status in 2017 after promising early trials, but in 2024 the agency voted against approval, citing concerns about trial design, blinding failures, and allegations of potential misconduct. The FDA has since issued updated guidance for future psychedelic trials, and research continues.
Microdosing
Microdosing involves taking a fraction of a full hallucinogenic dose, too small to produce any noticeable perceptual changes, on a regular schedule. The goal is not to “trip” but to subtly improve mood, focus, or creativity over time. For psilocybin mushrooms, a microdose typically falls between 0.1 and 0.5 grams of dried material, roughly equivalent to about 5 micrograms of LSD at the low end.
The most popular schedule, proposed by researcher James Fadiman, follows a simple pattern: one dosing day, then two days off, repeated over weeks or months. Some people follow other schedules or dose for periods ranging from a single week to several years. It’s worth noting that microdosing originated as an underground practice and still lacks standardized, widely accepted protocols. A double-blind placebo-controlled study published in Translational Psychiatry highlighted this lack of standardization as a significant limitation in evaluating whether microdosing truly works beyond placebo effects.
Recreational Use
Outside clinical and ceremonial settings, hallucinogens are used recreationally for the altered states of consciousness they produce: vivid visual distortions, shifts in time perception, intensified emotions, and feelings of connection or insight. LSD, psilocybin mushrooms, and DMT are among the most common. Doses in recreational contexts are typically much higher than microdoses but vary widely depending on the substance and the user’s experience.
The concept of “set and setting” applies across all contexts but is especially relevant here. “Set” refers to your mindset going in, including your mood, expectations, and mental health history. “Setting” refers to the physical and social environment. Researchers have identified four basic modalities: therapeutic, clinical trial, ritualistic, and recreational, each with different parameters for safety and outcomes. In recreational use, where professional support is absent, attention to set and setting becomes one of the most important harm reduction strategies.
Risks and Drug Interactions
Hallucinogens carry real risks, particularly when combined with other substances. One of the most dangerous interactions involves ayahuasca and common antidepressants. Ayahuasca contains natural compounds that block an enzyme responsible for breaking down serotonin. If you’re also taking an SSRI or SNRI (medications like fluoxetine, sertraline, citalopram, or paroxetine), serotonin can accumulate to dangerous levels in the brain. This condition, serotonin toxicity, can be life-threatening. Case reports have documented symptoms resembling serotonin toxicity after someone took ayahuasca while on fluoxetine.
Lithium, commonly prescribed for bipolar disorder, poses another serious risk. There are multiple reported cases of seizures occurring when lithium was combined with LSD or psilocybin. On the other end of the spectrum, certain medications can simply cancel out a hallucinogen’s effects entirely. Antipsychotics and some antidepressants that block serotonin receptors, including mirtazapine and risperidone, are expected to significantly diminish or eliminate the psychedelic experience.
A longer-term risk is hallucinogen persisting perception disorder, or HPPD, where visual disturbances that first appeared during a trip continue recurring afterward. Symptoms are primarily visual: trailing images, halos, geometric patterns, or flickering in the visual field. The DSM-5 estimates a prevalence of about 4.2% among hallucinogen users, though researchers acknowledge that reliable numbers are hard to pin down. HPPD comes in two forms: a mild, brief type with short flashbacks, and a more persistent type involving ongoing visual disturbances that cause significant distress.
Legal Status in the United States
Most hallucinogens remain Schedule I controlled substances under federal law, meaning they are illegal to manufacture, possess, or distribute. But the legal landscape is changing at the state and city level. Oregon became the first state to create a regulated framework for psilocybin therapy. Colorado followed in 2022, when voters passed Proposition 122 to establish its own regulated access model. Several California cities, including Oakland, Santa Cruz, Arcata, Berkeley, and San Francisco, have unanimously passed resolutions making personal use and possession of certain psychedelics the lowest priority for law enforcement. These local measures do not legalize the substances but effectively signal that police and prosecutors should focus resources elsewhere.
The gap between federal prohibition and state-level reform creates a complicated patchwork. Therapeutic use in clinical trials remains legal under FDA oversight regardless of a substance’s schedule status, which is how psilocybin and MDMA trials have proceeded. But outside of approved research or the handful of state programs, possession still carries legal consequences in most of the country.