Addiction: Hallucinogens


In brief, hallucinogens cause people to experience hallucinations, imagined experiences that seem real. Some hallucinogens can be found in plants. Mescaline comes from a cactus called peyote. And certain mushrooms, also known as magic mushrooms, are hallucinogens. But many hallucinogens are chemicals that don’t occur in nature. Some examples are:

  • LSD, also called acid  
  • MDA, an amphetamine  
  • MDMA, an amphetamine, called ecstasy  
  • PCP (phencyclidine), often called angel dust

What follows is a more detailed definition. Hallucinogens are drugs that cause hallucinations - profound distortions in a person’s perceptions of reality. Under the influence of hallucinogens, people see images, hear sounds, and feel sensations that seem real but do not exist. Some hallucinogens also produce rapid, intense emotional swings.

Hallucinogens cause their effects by disrupting the interaction of nerve cells and the neurotransmitter serotonin. Distributed throughout the brain and spinal cord, the serotonin system is involved in the control of behavioral, perceptual, and regulatory systems, including mood, hunger, body temperature, sexual behavior, muscle control, and sensory perception.

LSD (an abbreviation of the German words for “lysergic acid diethylamide”) is the drug most commonly identified with the term “hallucinogen” and the most widely used in this class of drugs. It is considered the typical hallucinogen, and the characteristics of its action and effects described in this Research Report apply to the other hallucinogens, including mescaline, psilocybin, and ibogaine.

Physical characteristics of LSD

LSD is a clear or white, odorless, water-soluble material synthesized from lysergic acid, a compound derived from a rye fungus. LSD is the most potent mood- and perception-altering drug known: oral doses as small as 30 micrograms can produce effects that last 6 to 12 hours.

LSD is initially produced in crystalline form. The pure crystal can be crushed to powder and mixed with binding agents to produce tablets known as “microdots” or thin squares of gelatin called “window panes”; more commonly, it is dissolved, diluted, and applied to paper or other materials. The most common form of LSD is called “blotter acid” - sheets of paper soaked in LSD and perforated into 1/4-inch square dosage units. Variations in manufacturing and the presence of contaminants can produce LSD in colors ranging from clear or white, in its purest form, to tan or even black. Even uncontaminated LSD begins to degrade and discolor soon after it is manufactured, and drug distributors often apply LSD to colored paper, making it difficult for a buyer to determine the drug’s purity or age.

What are dissociative drugs?

PCP, developed in the 1950s as an intravenous surgical anesthetic, is classified as a dissociative anesthetic: Its sedative and anesthetic effects are trance-like, and patients experience a feeling of being “out of body” and detached from their environment. PCP was used in veterinary medicine but was never approved for human use because of problems that arose during clinical studies, including delirium and extreme agitation experienced by patients emerging from anesthesia.

During the 1960s, PCP in pill form became widely abused, but the surge in illicit use receded rapidly as users became dissatisfied with the long delay between taking the drug and feeling its effects, and with the unpredictable and often violent behavior associated with its use. Powdered PCP - known as “ozone,” “rocket fuel,” “love boat,” “hog,” “embalming fluid,” or “superweed” - appeared in the 1970s. In powdered form, the drug is sprinkled on marijuana, tobacco, or parsley, and then smoked, and the onset of effects is rapid. Users sometimes ingest PCP by snorting the powder or by swallowing it in tablet form. Normally a white crystalline powder, PCP is sometimes colored with water-soluble or alcohol-soluble dyes.

When snorted or smoked, PCP rapidly passes to the brain to disrupt the functioning of sites known as NMDA (N-methyl-D-aspartate) receptor complexes, which are receptors for the neurotransmitter glutamate. Glutamate receptors play a major role in the perception of pain, in cognition - including learning and memory - and in emotion. In the brain, PCP also alters the actions of dopamine, a neurotransmitter responsible for the euphoria and “rush” associated with many abused drugs.

At low PCP doses (5 mg or less), physical effects include shallow, rapid breathing, increased blood pressure and heart rate, and elevated temperature. Doses of 10 mg or more cause dangerous changes in blood pressure, heart rate, and respiration, often accompanied by nausea, blurred vision, dizziness, and decreased awareness of pain. Muscle contractions may cause uncoordinated movements and bizarre postures. When severe, the muscle contractions can result in bone fracture or in kidney damage or failure as a consequence of muscle cells breaking down. Very high doses of PCP can cause convulsions, coma, hyperthermia, and death.

PCP’s effects are unpredictable. Typically, they are felt within minutes of ingestion and last for several hours. Some users report feeling the drug’s effects for days. One drug-taking episode may produce feelings of detachment from reality, including distortions of space, time, and body image; another may produce hallucinations, panic, and fear. Some users report feelings of invulnerability and exaggerated strength. PCP users may become severely disoriented, violent, or suicidal.

Repeated use of PCP can result in addiction, and recent research suggests that repeated or prolonged use of PCP can cause withdrawal syndrome when drug use is stopped. Symptoms such as memory loss and depression may persist for as long as a year after a chronic user stops taking PCP.

Nature and effects of ketamine

Ketamine (“K,” “Special K,” “cat Valium”) is a dissociative anesthetic developed in 1963 to replace PCP and currently used in human anesthesia and veterinary medicine. Much of the ketamine sold on the street has been diverted from veterinarians’ offices. Although it is manufactured as an injectable liquid, in illicit use ketamine is generally evaporated to form a powder that is snorted or compressed into pills.

Ketamine’s chemical structure and mechanism of action are similar to those of PCP, and its effects are similar, but ketamine is much less potent than PCP with effects of much shorter duration. Users report sensations ranging from a pleasant feeling of floating to being separated from their bodies. Some ketamine experiences involve a terrifying feeling of almost complete sensory detachment that is likened to a near-death experience. These experiences, similar to a “bad trip” on LSD, are called the “K-hole.” Ketamine is odorless and tasteless, so it can be added to beverages without being detected, and it induces amnesia. Because of these properties, the drug is sometimes given to unsuspecting victims and used in the commission of sexual assaults referred to as “drug rape.”

Nature and effects of dextromethorphan

Dextromethorphan (sometimes called “DXM” or “robo”) is a cough-suppressing ingredient in a variety of over-the-counter cold and cough medications. Like PCP and ketamine, dextromethorphan acts as an NMDA receptor antagonist. The most common source of abused dextromethorphan is “extra-strength” cough syrup, which typically contains 3 milligrams of the drug per milliliter of syrup. At the doses recommended for treating coughs (1/6 to 1/3 ounce of medication, containing 15 mg to 30 mg dextromethorphan), the drug is safe and effective. At much higher doses (4 or more ounces), dextromethorphan produces dissociative effects similar to those of PCP and ketamine.

The effects vary with dose, and dextromethorphan users describe a set of distinct dose-dependent “plateaus” ranging from a mild stimulant effect with distorted visual perceptions at low (approximately 2-ounce) doses to a sense of complete dissociation from one’s body at doses of 10 ounces or more. The effects typically last for 6 hours. Over-the-counter medications that contain dextromethorphan often contain antihistamine and decongestant ingredients as well, and high doses of these mixtures can seriously increase risks of dextromethorphan abuse. Extra-Strength cough syrup is the most common source of abused dextromethorphan.

Side Effects

Hallucinogens powerfully affect the brain, distorting the way the senses work and changing impressions of time and space. People who use these drugs can have:

  • A hard time concentrating, communicating, or distinguishing between reality and illusion  
  • Panic attacks at the height of the drug experience  
  • Unsolicited repetitions of the drug experience, without further ingestion of the drug  
  • Body wide anesthetic with enhanced sensations and impaired perceptions, which may result in panic reactions and violent defensive behaviors  
  • Paranoia, auditory hallucinations, psychosis similar to schizophrenia  
  • Cardiac arrhythmias, seizures, muscle rigidity, acute renal failure, and death  
  • No pain response to injury during use

Health Hazards

MDMA and MDA cause neurons to release a neurotransmitter called serotonin, over-activating serotonin receptors. In animals, MDMA and MDA have been shown to damage and destroy nerve fibers of neurons that contain serotonin. This can affect mood, sleep, and control of heart rate. Changing growth patterns of serotonin neurons may cause changes in learning and memory.

LSD use can have many effects including sleeplessness, trembling, and raised heart rate, and blood pressure. LSD users may feel several emotions at once (including extreme terror), and their senses may seem to get crossed - giving the feeling of hearing colors and seeing sounds.


LSD’s effects

The precise mechanism by which LSD alters perceptions is still unclear. Evidence from laboratory studies suggests that LSD, like hallucinogenic plants, acts on certain groups of serotonin receptors designated the 5-HT2 receptors, and that its effects are most prominent in two brain regions: One is the cerebral cortex, an area involved in mood, cognition, and perception; the other is the locus ceruleus, which receives sensory signals from all areas of the body and has been described as the brain’s “novelty detector” for important external stimuli.

LSD’s effects typically begin within 30 to 90 minutes of ingestion and may last as long as 12 hours. Users refer to LSD and other hallucinogenic experiences as “trips” and to the acute adverse experiences as “bad trips.” Although most LSD trips include both pleasant and unpleasant aspects, the drug’s effects are unpredictable and may vary with the amount ingested and the user’s personality, mood, expectations, and surroundings.

Users of LSD may experience some physiological effects, such as increased blood pressure and heart rate, dizziness, loss of appetite, dry mouth, sweating, nausea, numbness, and tremors; but the drug’s major effects are emotional and sensory. The user’s emotions may shift rapidly through a range from fear to euphoria, with transitions so rapid that the user may seem to experience several emotions simultaneously.

LSD also has dramatic effects on the senses. Colors, smells, sounds, and other sensations seem highly intensified. In some cases, sensory perceptions may blend in a phenomenon known as synesthesia, in which a person seems to hear or feel colors and see sounds.

Hallucinations distort or transform shapes and movements, and they may give rise to a perception that time is moving very slowly or that the user’s body is changing shape. On some trips, users experience sensations that are enjoyable and mentally stimulating and that produce a sense of heightened understanding. Bad trips, however, include terrifying thoughts and nightmarish feelings of anxiety and despair that include fears of insanity, death, or losing control.

LSD users quickly develop a high degree of tolerance for the drug’s effects: After repeated use, they need increasingly larger doses to produce similar effects. LSD use also produces tolerance for other hallucinogenic drugs such as psilocybin and mescaline, but not to drugs such as marijuana, amphetamines, and PCP, which do not act directly on the serotonin receptors affected by LSD. Tolerance for LSD is short-lived it is lost if the user stops taking the drug for several days. There is no evidence that LSD produces physical withdrawal symptoms when chronic use is stopped.

Two long-term effects are persistent psychosis and hallucinogen persisting perception disorder (HPPD), more commonly referred to as “flashbacks”-have been associated with use of LSD. The causes of these effects, which in some users occur after a single experience with the drug, are not known.

Psychosis. The effects of LSD can be described as drug-induced psychosis-distortion or disorganization of a person’s capacity to recognize reality, think rationally, or communicate with others. Some LSD users experience devastating psychological effects that persist after the trip has ended, producing a long-lasting psychotic-like state. LSD-induced persistent psychosis may include dramatic mood swings from mania to profound depression, vivid visual disturbances, and hallucinations. These effects may last for years and can affect people who have no history or other symptoms of psychological disorder.

Hallucinogen Persisting Perception Disorder

Some former LSD users report experiences known colloquially as “flashbacks” and called “HPPD” by physicians. These episodes are spontaneous, repeated, sometimes continuous recurrences of some of the sensory distortions originally produced by LSD. The experience may include hallucinations, but it most commonly consists of visual disturbances such as seeing false motion on the edges of the field of vision, bright or colored flashes, and halos or trails attached to moving objects. This condition is typically persistent and in some cases remains unchanged for years after individuals have stopped using the drug.

Because HPPD symptoms may be mistaken for those of other neurological disorders such as stroke or brain tumors, sufferers may consult a variety of clinicians before the disorder is accurately diagnosed. There is no established treatment for HPPD, although some antidepressant drugs may reduce the symptoms. Psychotherapy may help patients adjust to the confusion associated with visual distraction and to minimize the fear, expressed by some, that they are suffering brain damage or psychiatric disorder.


Why do people take hallucinogens?

Chemist Albert Hofmann, working at the Sandoz Corporation pharmaceutical laboratory in Switzerland, first synthesized LSD in 1938. He was conducting research on possible medical applications of various lysergic acid compounds derived from ergot, a fungus that develops on rye grass. Searching for compounds with therapeutic value, Hofmann created more than two dozen ergot-derived synthetic molecules. The 25th was called, in German, Lyserg-Sa"ure-Dia"thylamid 25, or LSD-25. Five years after he first created the drug, Hofmann accidentally ingested a small amount and experienced a series of frightening sensory effects:

“My surroundings . . . transformed themselves in more terrifying ways. Everything in the room spun around, and the familiar objects and pieces of furniture assumed grotesque, threatening forms. They were in continuous motion, animated, as if driven by an inner restlessness . . . . Even worse than these demonic transformations of the outer world were the alterations that I perceived in myself, in my inner being. Every exertion of my will, every attempt to put an end to the disintegration of the outer world and the dissolution of my ego, seemed to be wasted effort. A demon had invaded me, had taken possession of my body, mind, and soul.”

Hallucinogenic drugs have played a role in human life for thousands of years. Cultures from the tropics to the arctic have used plants to induce states of detachment from reality and to precipitate “visions” thought to provide mystical insight. These plants contain chemical compounds, such as mescaline, psilocybin, and ibogaine, that are structurally similar to serotonin, and they produce their effects by disrupting normal functioning of the serotonin system. Historically, hallucinogenic plants were used largely for social and religious ritual, and their availability was limited by the climate and soil conditions they require. After the development of LSD, a synthetic compound that can be manufactured anywhere, abuse of hallucinogens became more widespread, and from the 1960s it increased dramatically. All LSD manufactured in this country is intended for illegal use, since LSD has no accepted medical use in the United States.


Success in becoming “drug free” is best achieved through formal programs in conjunction with community-based support programs. Comprehensive residential treatment programs monitor and address potential withdrawal symptoms/behaviors; incorporate behavior recognition and modification programs; include psychotherapeutic treatments both for the person (and perhaps family) and in-group settings; have a prolonged after-care component; and facilitate peer support. Drug addiction is a serious and complicated health condition that requires both physiological and psychological treatment and support.

Drug addiction is a treatable disorder. Through treatment that is tailored to individual needs, patients can learn to control their condition and live normal, productive lives. Like people with diabetes or heart disease, people in treatment for drug addictions learn behavioral changes and often take medications as part of their treatment regimen.

Behavioral therapies can include counseling, psychotherapy, support groups, or family therapy. Treatment medications offer help in suppressing the withdrawal syndrome and drug craving and in blocking the effects of drugs. In addition, studies show that treatment for heroin addiction using methadone at an adequate dosage level combined with behavioral therapy reduces death rates and many health problems associated with heroin abuse.

In general, the more treatments that are given, the better the results. Many patients require other services as well, such as medical and mental health services and HIV prevention services. Patients who stay in treatment longer than 3 months usually have better outcomes than those who stay less time. Patients who go through medically assisted withdrawal to minimize discomfort but do not receive any further treatment, perform about the same in terms of their drug use as those who were never treated. Over the last 25 years, studies have shown that treatment works to reduce drug intake and crimes committed by drug-dependent people. Researchers also have found that drug abusers who have been through treatment are more likely to have jobs.

Types of Treatment Programs

The ultimate goal of all drug abuse treatment is to enable the patient to achieve lasting abstinence, but the immediate goals are to reduce drug use, improve the patient’s ability to function, and minimize the medical and social complications of drug abuse.

There are several types of drug abuse treatment programs. Short-term methods last less than 6 months and include residential therapy, medication therapy, and drug-free outpatient therapy. Longer-term treatment may include, for example, methadone maintenance outpatient treatment for opiate addicts and residential therapeutic community treatment.

In maintenance treatment for heroin addicts, people in treatment are given an oral dose of a synthetic opiate, usually methadone hydrochloride or levo-alpha-acetyl methadol (LAAM), administered at a dosage sufficient to block the effects of heroin and yield a stable, noneuphoric state free from physiological craving for opiates. In this stable state, the patient is able to disengage from drug-seeking and related criminal behavior and, with appropriate counseling and social services, become a productive member of his or her community.

Outpatient drug-free treatment does not include medications and encompasses a wide variety of programs for patients who visit a clinic at regular intervals. Most of the programs involve individual or group counseling. Patients entering these programs are abusers of drugs other than opiates or are opiate abusers for whom maintenance therapy is not recommended, such as those who have stable, well-integrated lives and only brief histories of drug dependence.

Therapeutic communities (TCs) are highly structured programs in which patients stay at a residence, typically for 6 to 12 months. Patients in TCs include those with relatively long histories of drug dependence, involvement in serious criminal activities, and seriously impaired social functioning. The focus of the TC is on the resocialization of the patient to a drug-free, crime-free lifestyle.

Short-term residential programs, often referred to as chemical dependency units, are often based on the “Minnesota Model” of treatment for alcoholism. These programs involve a 3- to 6-week inpatient treatment phase followed by extended outpatient therapy or participation in 12-step self-help groups, such as Narcotics Anonymous or Cocaine Anonymous. Chemical dependency programs for drug abuse arose in the private sector in the mid-1980s with insured alcohol/cocaine abusers as their primary patients. Today, as private provider benefits decline, more programs are extending their services to publicly funded patients.

Drug treatment programs in prisons can succeed in preventing patients’ return to criminal behavior, particularly if they are linked to community-based programs that continue treatment when the client leaves prison. Some of the more successful programs have reduced the rearrest rate by one-fourth to one-half. For example, the “Delaware Model,” an ongoing study of comprehensive treatment of drug- addicted prison inmates, shows that prison-based treatment including a therapeutic community setting, a work release therapeutic community, and community-based aftercare reduces the probability of rearrest by 57 percent and reduces the likelihood of returning to drug use by 37 percent.

Drug abuse has a great economic impact on society-an estimated $67 billion per year. This figure includes costs related to crime, medical care, drug abuse treatment, social welfare programs, and time lost from work. Treatment of drug abuse can reduce those costs. Studies have shown that from $4 to $7 are saved for every dollar spent on treatment. It costs approximately $3,600 per month to leave a drug abuser untreated in the community, and incarceration costs approximately $3,300 per month. In contrast, methadone maintenance therapy costs about $290 per month.

For information on hotlines or counseling services, please call the Center for Substance Abuse Treatment’s National Drug and Alcohol Treatment Service at 1-800-662-4357.

Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

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