Hallucinations are sensory experiences that feel real but are not caused by anything in the outside world. A range of drugs can produce them, including classic psychedelics like LSD and psilocybin, dissociatives like ketamine and PCP, stimulants like methamphetamine and cocaine at high doses, and certain prescription medications. Alcohol withdrawal and some over-the-counter drugs can also trigger hallucinations.
What makes a drug hallucinogenic comes down to how it disrupts the brain’s normal processing of sensory information. Different classes of drugs do this in different ways, which is why the experience of a hallucination on LSD looks very different from one caused by ketamine or by alcohol withdrawal.
What Drugs Make You Hallucinate?
The drugs most reliably associated with hallucinations fall into several categories. Each produces a distinct type of experience because each affects the brain differently.
Classic psychedelics include LSD, psilocybin (found in magic mushrooms), mescaline (found in peyote and some cacti), and DMT. These primarily affect serotonin receptors, particularly the 5-HT2A receptor. Hallucinations from this group tend to involve vivid visual distortions, geometric patterns, and altered perception of time and space.
Dissociatives include ketamine, PCP, and dextromethorphan at high doses. These work mainly on NMDA receptors. The hallucinations they produce often involve feelings of detachment from the body, out-of-body experiences, and a sense of unreality rather than the colorful visual patterns of classic psychedelics.
Stimulants like methamphetamine and cocaine can cause hallucinations, especially with heavy or prolonged use. These are typically auditory and tactile rather than visual. A person may hear voices or feel things crawling on their skin.
Cannabis at high doses, particularly edible forms, can produce mild visual distortions and, in some people, frank hallucinations. This is more common in inexperienced users or with very high doses.
Prescription medications that can cause hallucinations include certain sleep aids, some antidepressants, antiparkinsonian drugs, and certain pain medications. This is not a complete list, and anyone concerned about a medication should speak with their prescriber.
How Do Hallucinogenic Drugs Affect the Brain?
Hallucinogens disrupt the brain’s normal filtering and integration of sensory information. The brain constantly receives signals from the eyes, ears, skin, and internal organs. Under normal conditions, it sorts these signals into a coherent picture of reality.
Classic psychedelics like LSD and psilocybin activate serotonin 5-HT2A receptors in the cortex. This appears to increase communication between brain regions that do not normally talk to each other. Brain imaging studies have shown that this can disrupt the default mode network, a set of brain regions active during rest and self-reflection. The result is a blending of senses and thoughts that the brain interprets as hallucinations.
Dissociatives like ketamine block NMDA receptors, which are involved in learning, memory, and pain perception. This blockade can cause the brain to lose its normal sense of where the body ends and the world begins, leading to feelings of detachment and, at higher doses, full hallucinations.
Stimulants work differently. They flood the brain with dopamine and norepinephrine. With repeated high-dose use, the brain may start to misinterpret internal signals as external voices or sensations. This is why stimulant-induced hallucinations are often auditory or tactile.
One important clarification: hallucinations are not the same as delusions. A hallucination is a false sensory experience. A delusion is a false belief. Some drugs cause both, but they are distinct phenomena.
What Is the Difference Between Hallucinations and Other Sensory Distortions?
Not every unusual sensory experience is a hallucination. The distinction matters for understanding what a drug is doing and for getting appropriate help.
A hallucination is a sensory experience that occurs without an external stimulus. Hearing a voice when no one is speaking is an auditory hallucination. Seeing a pattern on a blank wall is a visual hallucination.
An illusion is a misinterpretation of a real stimulus. Seeing a shadow and thinking it is a person is an illusion. The shadow is real; the interpretation is wrong.
A distortion is a change in how a real stimulus appears. Colors looking brighter or sounds seeming louder are distortions. The stimulus is present but perceived differently.
Classic psychedelics often produce more distortions and illusions than true hallucinations. A person on LSD may see walls breathing or colors shifting, but they usually know these experiences are drug-induced. Dissociatives and stimulants are more likely to produce true hallucinations where the person believes the experience is real.
Can Prescription Medications Cause Hallucinations?
Yes. Several classes of prescription drugs can cause hallucinations as a side effect. This is more common in older adults, people taking multiple medications, and those with underlying medical conditions.
Medications that have been associated with hallucinations include:
- Certain sleep medications, including some benzodiazepine receptor agonists
- Some antidepressants, particularly at high doses or in combination with other drugs
- Antiparkinsonian drugs that affect dopamine
- Certain opioids and anesthetic agents
- Some corticosteroids at high doses
- Certain antibiotics and antivirals
This list is not exhaustive. Any medication that affects neurotransmitters can potentially cause hallucinations in susceptible individuals. The risk is higher with polypharmacy, meaning the use of multiple medications at the same time.
Anyone who experiences hallucinations while taking a prescription medication should contact their prescriber. Do not stop a medication suddenly without medical guidance, as some drugs can cause dangerous withdrawal effects.
Can Alcohol Cause Hallucinations?
Alcohol can cause hallucinations in two distinct situations: during severe intoxication and during withdrawal.
During heavy drinking, some people experience brief hallucinations, often auditory or visual. These are more common in people who have been drinking heavily for years.
Alcohol withdrawal is a more serious cause. When a person who is dependent on alcohol suddenly stops or significantly reduces their intake, the brain’s chemistry is thrown off balance. This can lead to a condition called delirium tremens, which includes confusion, agitation, fever, and vivid hallucinations. Delirium tremens is a medical emergency and can be fatal without treatment.
Hallucinations during alcohol withdrawal typically begin within 12 to 48 hours after the last drink and can last for several days. Anyone experiencing these symptoms needs immediate medical attention.
What Should You Do If Someone Is Hallucinating?
If someone is hallucinating, the first step is to assess whether it is a medical emergency. Signs that require immediate help include confusion, fever, rapid heart rate, seizures, or a sudden change in consciousness.
If the person is not in immediate danger, stay calm and keep the environment quiet and safe. Do not argue with them about what they are seeing or hearing. Instead, acknowledge their experience without confirming it. You might say, “I understand you are seeing something that is frightening to you. I am here with you.”
Do not try to restrain someone who is hallucinating unless they are in immediate danger of harming themselves or others. Restraint can increase agitation and the risk of injury.
If the hallucinations are caused by a known drug use, keep the person hydrated and monitor their breathing. If they become unresponsive or have trouble breathing, call emergency services.
For hallucinations that are not a medical emergency, a medical evaluation is still important. A doctor can help determine whether the cause is a drug, a medication side effect, a mental health condition, or another medical issue.
Are Hallucinations Always a Sign of a Serious Problem?
Not always, but they should never be ignored. Hallucinations can be a normal part of certain drug experiences, a side effect of medication, a symptom of a mental health condition, or a sign of a medical emergency.
The context matters. A person who knowingly took a psychedelic and is having visual distortions is in a different situation from someone who suddenly starts hearing voices with no obvious cause. The first is expected; the second requires medical evaluation.
Recurrent hallucinations, especially auditory ones, can be a symptom of schizophrenia or another psychotic disorder. They can also occur in severe depression, bipolar disorder, and post-traumatic stress disorder. Medical conditions like epilepsy, migraines, brain tumors, and infections can also cause hallucinations.
If you or someone you know is experiencing hallucinations that are not explained by a known drug effect, seek medical evaluation. Early assessment can rule out serious causes and connect you with appropriate care.
Frequently Asked Questions
What drugs are most likely to make you hallucinate?
Classic psychedelics like LSD and psilocybin, dissociatives like ketamine and PCP, and stimulants like methamphetamine are the drugs most commonly associated with hallucinations. Prescription medications and alcohol withdrawal can also cause them.
Can you hallucinate from marijuana?
High doses of cannabis, especially edible forms, can cause mild visual distortions and, in some people, true hallucinations. This is more common in inexperienced users or with very large doses.
How long do drug-induced hallucinations last?
The duration depends on the drug. LSD effects typically last 8 to 12 hours, psilocybin 4 to 6 hours, and ketamine 1 to 2 hours. Stimulant-induced hallucinations can persist for days or longer with heavy use.
Are hallucinations dangerous?
Hallucinations themselves are not physically dangerous, but they can lead to accidents, injuries, or risky behavior if the person cannot tell what is real. Some causes, like alcohol withdrawal, are medical emergencies.
