Hallucinogens affect the brain by disrupting the chemical signals that shape perception, mood and thought. Classic psychedelics like LSD, psilocybin and mescaline mostly act on serotonin receptors, especially in the prefrontal cortex. Other hallucinogens work through entirely different systems. The result can be distorted senses, a warped sense of time and self, and intense emotion. For some people, the effects linger long after the drug is gone.
A man sits with his head in his hands, thinking about hallucinogen effects on the brain.
Heart rate, temperature and other physical effects are covered in our companion post on how hallucinogens affect the body. Here, the focus is the mind, in the short term and the long term.
The Main Types of Hallucinogens and How They Work
“Hallucinogen” is a broad label. Different drugs get to similar effects through different doors in the brain.
Psychedelics: serotonin
LSD, psilocybin (“magic mushrooms”), mescaline and DMT activate a type of serotonin receptor called 5-HT2A. Those receptors are packed into the prefrontal cortex, the part of the brain involved in perception, mood, planning and making sense of experience. Overstimulate them and the way sensory information gets filtered and interpreted is scrambled. Colors may seem to breathe. Sounds may seem to have shape, and familiar thoughts can feel strange or profound. Our post on mescaline side effects walks through one example.
Dissociatives: glutamate
PCP, ketamine and DXM block NMDA receptors, which respond to glutamate, one of the brain’s main signaling chemicals. What people feel is detachment from their body and surroundings, numbness, gaps in memory and a sense that the world isn’t real.
Salvia: kappa opioid receptors
Salvinorin A, the active compound in salvia divinorum, acts on kappa opioid receptors instead of serotonin. That may be why salvia’s effects are so unusual: fast, short and often deeply disorienting. There’s more in salvia divinorum effects.
Deliriants: acetylcholine
Plants such as datura (jimsonweed) block acetylcholine receptors. You don’t get visual patterns. You get true delirium, with extreme confusion, no ability to tell what’s real and no control over what you’re doing. Deliriants are among the most dangerous hallucinogens there are.
What Happens in the Brain During a Trip
In the short term, hallucinogens can change:
- Perception, with visual distortions, senses blending together, and altered sounds and body sensations
- Time: minutes can feel like hours, or time can seem to stop
- Sense of self, such as feeling detached from your body or like the line between you and your surroundings has dissolved
- Emotion. The National Institute on Drug Abuse notes these drugs can produce strong emotions ranging from bliss to fear.
- Thinking, including racing thoughts, confusion, poor judgment and trouble telling what’s real
Why a Trip Can’t Be Controlled
People talk about “set and setting,” the idea that mood, expectations and surroundings shape a trip. Those things matter. They don’t put anyone in control. The same drug from the same source can bring a peaceful experience one time and terror the next. Street hallucinogens are often mislabeled or mixed with other substances, too, so the person may not even be taking what they think. Once a trip starts, it has to run its course, and with some drugs that means many hours.
Long-Term Effects of Hallucinogens on the Brain
Hallucinogen persisting perception disorder (HPPD)
HPPD is a recognized diagnosis in the DSM-5. People who have it keep seeing visual disturbances after the drug has worn off: visual “snow,” trails behind moving objects, halos around lights, intensified colors or afterimages. For some it comes as brief flashbacks. For others it’s close to constant. HPPD has been reported after a single use, most notably of LSD, and it can be distressing and hard to treat.
Persistent psychosis
Hallucinogens can trigger psychotic symptoms like paranoia, disorganized thinking and hallucinations that don’t fade when the drug does. It’s uncommon. The risk is higher, though, for people with a personal or family history of schizophrenia, bipolar disorder or other serious mental illness, and many don’t know they carry that risk until it’s too late.
Tolerance
With repeated use, the brain quickly becomes less responsive to psychedelics, and tolerance to one carries over to others, say from LSD to psilocybin or mescaline. People chasing the original intensity may use more, use more often or move on to other drugs.
Mood and anxiety
A frightening trip can leave behind lasting anxiety, panic attacks or depression. Repeated dissociative use is linked with memory and thinking problems. And for anyone using hallucinogens to escape, whatever they were escaping is still waiting when the drug wears off.
What About Psychedelic Research?
NIDA notes growing research interest in whether psychedelic and dissociative drugs could treat certain mental health conditions. That research uses carefully measured, tested substances. It screens out people at high risk and provides close clinical support. Taking street hallucinogens on your own is a very different situation, with none of those protections.
Christian-Based Treatment for Hallucinogen Use at Covenant Hills
At Covenant Hills in Orange County, we treat hallucinogen addiction alongside the anxiety, depression, trauma and other conditions that so often come with it, through our co-occurring disorders treatment. Clients can choose our faith-based track or a traditional track, and both are rooted in evidence-based care.
If hallucinogens are affecting your mind, your mood or your relationships, call 800-662-2873 for a free, confidential assessment.
Frequently Asked Questions
How do hallucinogens affect the brain?
Most psychedelics act on serotonin 5-HT2A receptors, especially in the prefrontal cortex, which alters perception, mood and thinking. Dissociatives block glutamate signaling. Salvia acts on kappa opioid receptors, and deliriants block acetylcholine.
Can hallucinogens cause permanent brain changes?
Some people develop lasting problems, including hallucinogen persisting perception disorder (ongoing visual disturbances) or persistent psychosis. They aren’t common, but they can follow even one use.
What is HPPD?
Hallucinogen persisting perception disorder is a condition where visual disturbances like trails, halos or visual snow keep happening long after someone has stopped using hallucinogens.
Are hallucinogens addictive?
Classic psychedelics are less likely to cause compulsive use than many drugs, but tolerance builds fast and psychological reliance is common. Some dissociatives, like PCP, carry a higher risk of problematic use.
