Hallucinogens carry risks that range from intense psychological distress during a single use to rare but serious physical emergencies, and some dangers have nothing to do with the drug itself. The specific risks depend heavily on the substance, the dose, the person’s mental health history, and whether what they took is actually what they think it is.
Bad Trips and Acute Psychological Crisis
The most common danger of hallucinogens is a severely distressing experience during intoxication. A “bad trip” can involve overwhelming panic, paranoia, a feeling of losing one’s mind, or terrifying visual distortions that feel completely real. These episodes are not just unpleasant. They can last hours, with substances like LSD producing effects for 8 to 12 hours and the user unable to stop or control the experience once it begins.
During this state, judgment and perception are deeply impaired. People may not recognize familiar surroundings, may misinterpret distances or heights, or may act on delusional beliefs. Falls, drowning, and traffic accidents have all been documented in people under the influence of psychoactive drugs, with falls and road traffic accidents accounting for the majority of unintentional fatal injuries in intoxicated individuals.
Triggering Lasting Psychiatric Episodes
For people with a genetic predisposition to schizophrenia or bipolar disorder, hallucinogens can act as a trigger for a full psychiatric episode. A 2024 study published in JAMA Psychiatry found significant interactions between psychedelic use and genetic vulnerability: adolescents with high genetic susceptibility to schizophrenia or bipolar I disorder experienced more psychotic or manic symptoms after using psychedelics compared to those with low genetic risk. The concern is that these episodes aren’t limited to the duration of the drug. They can persist and require ongoing psychiatric treatment.
One proposed mechanism is that psychedelics may activate a manic episode in a way similar to how some antidepressants can flip a person with bipolar disorder into mania. A family history of psychotic or mood disorders is the clearest known risk factor, but many people don’t know their full family psychiatric history, which makes this an unpredictable danger.
Hallucinogen Persisting Perception Disorder
Some people continue to experience visual disturbances long after a hallucinogen has left their system. This condition, known as HPPD, involves recurring perceptual distortions that first appeared during intoxication: trailing images behind moving objects, halos around lights, flashes of color, objects appearing too small or too large, or afterimages that linger after looking away. The DSM-5 estimates a prevalence of about 4.2% among hallucinogen users, though actual numbers are uncertain because the condition is frequently unrecognized.
HPPD can be brief and mild, or it can be chronic and distressing enough to interfere with daily life. Researchers distinguish between two types: one involving short, benign flashbacks, and another involving persistent, anxiety-provoking visual disturbances that match the formal diagnostic criteria. There is no established cure, and the condition remains poorly understood precisely because it is rare enough that large-scale studies are difficult to conduct.
Dangerous Drug Interactions
Combining hallucinogens with certain medications can cause serotonin toxicity, a potentially life-threatening condition where excess serotonin floods the nervous system. The highest risk comes from combining a psychedelic with a monoamine oxidase inhibitor (MAOI), a class of antidepressant. This combination is especially relevant for ayahuasca, which naturally contains an MAOI as one of its active components, meaning it carries inherent serotonin toxicity risk when combined with common antidepressants.
Symptoms of severe serotonin toxicity include muscle rigidity, dangerous fluctuations in heart rate and blood pressure, high fever, seizures, and altered consciousness ranging from agitation to coma. Notably, combining psychedelics with SSRIs (the most commonly prescribed antidepressants) without an MAOI present appears to carry lower risk, though it can still blunt or unpredictably alter the psychedelic experience.
Heart Risks With Specific Substances
Not all hallucinogens carry the same physical risks, and some pose direct threats to the heart. Ibogaine, a psychoactive substance derived from a West African plant and used in some addiction treatment settings, can cause dangerous disruptions to heart rhythm. It prolongs the electrical cycle of the heartbeat, creating a window where the heart is vulnerable to chaotic, potentially fatal rhythms.
In one documented case, a 61-year-old man’s heart rate spiked to 270 beats per minute after taking ibogaine, requiring emergency defibrillation. His heart’s electrical recovery took a full seven days to normalize. Sudden death after ibogaine ingestion has been reported in multiple cases and is thought to result from this same mechanism. People with pre-existing heart conditions or electrolyte imbalances face the highest risk, but cardiac events have occurred in otherwise healthy individuals as well.
Synthetic Imitations That Can Kill
One of the most serious and underappreciated dangers is taking a substance that isn’t what it’s sold as. NBOMe compounds, sometimes called “synthetic LSD,” are sold on blotter paper and can be visually indistinguishable from actual LSD. But their toxicity profile is dramatically different.
NBOMe substances cause seizures at a much higher rate than classical psychedelics. Severe cases can progress to a cascade of organ failure: muscle tissue breaks down, the blood becomes dangerously acidic, the kidneys shut down, and body temperature spikes to life-threatening levels. Uncontrollable violent behavior and extreme agitation are also more common. Unlike LSD, which has an extremely high threshold for a physically lethal dose, NBOMe compounds have a narrow margin between an active dose and a toxic one. Multiple deaths have been attributed to these substances when users believed they were taking LSD.
Poisonous Mushroom Lookalikes
People who forage for psilocybin mushrooms face a risk that has nothing to do with the psychoactive compound itself: deadly misidentification. Several species of small brown mushrooms in the genus Galerina look similar to psilocybin-containing species but contain amatoxins, the same lethal compounds found in the death cap mushroom. The lethal dose of amatoxins is remarkably small. As few as 10 Galerina mushrooms could poison a 44-pound child.
Amatoxin poisoning is deceptive. Initial symptoms of nausea and diarrhea may appear within hours, but the real damage is happening silently. Liver failure can set in around 72 hours after ingestion. In documented cases, victims have required extended hospitalization for liver and kidney damage, and fatalities have been reported. A family in Japan, a woman in Sweden who mistook Galerina for honey mushrooms, and a group of 13 coworkers in China who were accidentally served a contaminated dish all ended up hospitalized with organ damage.
Rising Emergency Room Visits
Hallucinogen-related emergency department and hospital admissions have been climbing. An analysis of U.S. insurance claims data from 2016 to 2023 found that hallucinogen-related admissions increased steadily from 2016 through April 2020, rising about 0.62% per month. While rates declined during the early pandemic period, they remained elevated compared to pre-2016 levels. Hallucinogens still account for a small share of all substance-related admissions (roughly 0.6% to 1.2%), but the upward trend reflects growing use and, likely, growing encounters with the risks described above.
The relatively low absolute numbers can create a false sense of safety. Many hallucinogen-related emergencies involve psychological crises, not overdoses, and some may be coded under other categories like anxiety or psychosis rather than substance use. The true burden on emergency services is likely higher than the data suggest.