What is HPPD? (Hallucinogen Persisting Perception Disorder)

Hallucinogen Persisting Perception Disorder (HPPD) – A Neglected Consequence of Using Mushrooms Acid, and other Psychedelics

Imagine what it would be like getting stuck inside a trip that lasts forever? This may sound like scary propaganda, but there are people who report feeling just like that, in a condition known as Hallucinogen persisting perception disorder (HPPD). It is one of the most poorly understood conditions, wherein people who have used psychedelics report lasting changes in their visual perception. The condition is little known even among psychiatrists and psychedelic experts, who often misdiagnose HPPD as drug-induced psychosis. But how likely is it to get HPPD? Which psychedelics cause it? Can it be avoided or mitigated? We explore these topics below.

What is Hallucinogen Persisting Perception Disorder (HPPD)?

What is Hallucinogen Persisting Perception Disorder (HPPD)?

HPPD is a condition where people have experienced distressing visual disturbances after taking a psychedelic, which remains permanent after the effects have worn off. Visual disturbances can last for many years, sometimes people get used to them or do not find them disturbing, to begin with, but for some people, it can last for years and years without knowing whether vision or their sense of reality will ever be normal again.

How Common Is HPPD?

Permanent changes in vision following a psychedelic may be more common than we think, some estimates say that 60% of psychedelic users report having abnormal visual experiences in a sober state. But many of these experiences are not distressing or very mild, so people do not seek out medical diagnoses. In the same survey, it is estimated that about 4% of psychedelic users develop HPPD, finding the symptoms so distressing that they need medical help. Similar estimates were reported by a 2010 survey from Imperial College, of 626 psychedelic users: 34% reported moderate lasting visual changes, and 6% reported extreme lasting visual changes.

Is HPPD Like Psychosis?

Superficially, HPPD symptoms may resemble psychosis because they may both include the presence of hallucinations. But unlike with most forms of psychosis, people suffering from HPPD experience visual changes as a stable feature that is embedded in their perception and can differentiate hallucinations from reality.

Psychosis is, by comparison, a more transient condition that can come and go in waves, and people often suffer from delusional thought patterns which make it difficult for them to tell the difference between mental fiction and reality.

HPPD should not be confused with psychosis, since these conditions require very different treatments!

HPPD Symptoms

Some people who encounter small visual changes may not necessarily become distressed by it, so this condition only describes mostly the severe outcomes. These include:

  • Visual hallucinations
  • Vibrant geometric shapes
  • Movement trails

Let’s take a closer look at what these symptoms look like and how they manifest.

Types of HPPD

Types of HPPD

There are many symptoms of HPPD that are based on the psychiatric dictionary called the Diagnostic and Statistical Manual of Mental Disorders (DSM). Other information comes from Reddit forums and online communities of people suffering from the condition.

Type 1 HPPD (“Flashback”)

Type 1 consists of recurrent periodic episodes, wherein people relive past psychedelic experiences. Often referred to as ‘flashbacks’ a term that was first coined by Mardi J. Horrowitz in 1969. Since then, it has often been falsely claimed that psychedelics are permanently stored within the spinal column and become spontaneously released and induce psychedelic experiences unexpectedly. This has been debunked, and flashbacks are actually extremely rare! Different estimates place the frequency of flashbacks between 1 in 20 people or even 1 in 50 000 people who experience flashbacks after taking a psychedelic. One important exception is the drug 5-Meo-DMT, where even up to 69% of users experience flashbacks. By comparison, N, N-DMT does not seem to occasion such reports.

Type 2 HPPD (“Endless Trip”)

Type 2 HPPD is a chronic condition, whereby people experience lasting hallucinations in their day-to-day lives. In fact, Jean-Paul Sartre developed Type 2 HPPD after being injected with mescaline in a Hospital.

This type was classified by Dr. Henry Abraham in 1983 after working with patients since the 70s, and still working with them up to this date. According to Abraham, HPPD is essentially a type of visual tinnitus, where visual noise filtering becomes disinhibited. This can cause lasting hallucinations in the form of afterimages, halos, trails, or visual snow.

Let’s explore these in greater detail:

What Does HPPD Look Like?

What Does HPPD Look Like?

There is no universal symptom profile for HPPD. The condition is so rare that it can be difficult to diagnose because there is barely any information available about it. The condition is characterized by visual disturbances that are usually mild in nature. Some people experience more severe symptoms.

Visual Snow

Your field of vision is covered with TV static, which looks like suspended particles in the air.

Halos and Auras

Objects in your surrounding are illuminated with light.

Trails and Tracers

Moving objects have a faint trail of a replicated image following behind.

After Images

The silhouette of objects remains seen after looking away, in the same way as when people look at bright objects.

Intensified Floaters

Floaters are usually seen when people look at bright objects or the sky. They look like threads or squiggly lines. Typically, these are short-lived images, but they are much more intense and long-lasting for some people suffering from HPPD.

Tunnel Vision

The borders of vision become blurred out, start melting or become fuzzy.

Complex imagery

This may include more full-blown psychedelic phenomena like geometric patterns, melting walls, swirling shapes.

Auditory Changes

Some people report getting tinnitus as part of their HPPD symptoms.

Dream and Sleep

Psychedelics have important effects on sleep, and some people report having much more intense hypnagogic visual hallucinations while they are falling asleep.

What Does HPPD Feel Like?

HPPD is most often linked to visual changes, but there are also some important emotional, bodily, and cognitive changes worth considering.

Somatic Changes

Some people report feeling increased head pressure or unexpected tactile vibrations on different parts of the body.

Cognitive Disruptions

Some people develop thought loopsdyslexia, or stammer.

Depersonalization/Derealization Disorder Following Psychedelics

Over 90% of HPPD sufferers also report suffering from Depersonalization/Derealization Disorder. They describe it as a state of being trapped inside their own body while being disconnected from what they are doing, they report that they feel as they are interacting with the world like a robot.

Everything feels dream-like, unreal, and alien. This may be a consequence of dissociating from visual intrusions.

Emotional Disturbances

For some people, these perceptual changes can be so intense that they are acutely impaired in daily life and also suffer from panic, depression, and anxiety. The lasting nature of these symptoms has even prompted suicidal ideation and completed suicides.

Which Drugs Cause Hallucinogen Persisting Perception Disorder (HPPD)?

Which Drugs Cause Hallucinogen Persisting Perception Disorder (HPPD)?

HPPD is caused by a number of different drugs. It is not clear whether HPPD is caused by the drug itself, or by some other factor such as the person's underlying mental health status. Individual differences between these drugs are not well known, but synthetic drugs like LSD, MDMA, or 2-CB carry an additional risk of contamination with Novel Psychoactive Substances.

Let’s review these different drugs:


LSD chemical structure
LSD chemical structure

LSD is classified as the leading cause of HPPD, but this is because it is the most commonly used psychedelic drug. It is not known whether it is particularly risky compared to other psychedelics, such as 2-CB, magic mushrooms, ayahuasca, or mescaline.


5 MeO DMT(5-Methoxy-N, N-Dimethyltryptamine) chemical structure
5-MeO DMT(5-Methoxy-N, N-Dimethyltryptamine) chemical structure

5-Meo-DMT is a very powerful psychedelic substance, its effects are in fact so intense, that people often report “flashbacks” or spontaneous “reactivations” where they vividly re-experience its effects. Researchers believe this is because the subjective effects are so intense, not all of it is processed during the acute experience. A study found that up to 69% of people who use vaporized 5-Meo-DMT encounter “flashbacks”, however, this is about 50% lower among people who use intramuscular injection to administer 5-Meo-DMT. Similar anecdotal reports have not been raised in relation to N, N-DMT, but as of yet, they have not been systematically compared within a scientific study.


THC chemical structure
THC chemical structure

Although it is unlikely to get HPPD from weed, it can intensify the symptoms of an already existing HPPD. There is a subgroup of Reddit users who report their cannabis trips became (more) psychedelic after they had used DMT previously on a different occasion. Cannabis in turn can also make psychedelics trippier when used in combination. Cannabis is therefore considered to be a psychedelic-enhancer, and according to some reports, cannabis can also act as an HPPD-trigger or make existing HPPD symptoms permanently worse.


MDMA chemical structure
MDMA chemical structure

MDMA is one of the synthetic drugs that is often contaminated with other Novel Psychoactive substances, such as 2-CB or 4-FA. Many of these substances have only recently been synthesized, so long-term risks, such as HPPD, are not yet known. MDMA is frequently contaminated with its byproduct MDA, which is reported to cause HPPD.


Ketamine chemical structure
Ketamine chemical structure

HPPD has also been reported following therapeutic ketamine, but risk assessment is again difficult. Since the drug is also synthetic, contamination is more easily possible.

Non-Psychedelic or Psychoactive Drugs and HPPD

HPPD-like symptoms have also been observed in relation to non-psychedelic drugs like antibioticsSSRI antidepressantsnootropics, and antipsychotics.

Given that even non-psychedelic drugs can cause HPPD-like symptoms, there may be other internal or external factors causing this condition.

Why Do Psychedelic Drugs Cause HPPD?

Why Do Psychedelic Drugs Cause HPPD?

There is not a single case of HPPD that has been documented in the clinical context. This may change in the future, but it is also likely that the condition is caused by a mix of internal and external factors

Internal Factors: Neuroplasticity

Psychedelics such as LSD, psilocybin, and ketamine induce neuroplasticity, the ability of the brain to rewire and form new connections, which lasts up to one week after exposure to these drugs. There are many theories that explain how increasing neuroplasticity is beneficial for treating depression, but there has been very little research about the risk of having too much neuroplasticity. For instance, it is not known how dormant trauma interacts with neuroplasticity, leading to the brain rewiring itself in distressing ways, leading to HPPD. This is just a hypothesis, but children for example already have a lot of natural neuroplasticity, so they may be at greater risk of developing HPPD if they use psychedelics at an early age (more research is needed to confirm this).

External Factors: Environmental Triggers and Setting

People suffering from HPPD report that their condition is triggered or intensified by tiredness, stimulation, anxiety, and distress. Psychedelics are often used recreationally in the context of loud parties, a lack of sleep, and lots of audiovisual stimulation. It is possible that these environments contribute to the over-stimulation of the psyche, or reduce people’s capacity to integrate challenging experiences.

HPPD Prevention

HPPD Prevention

Let us review some best practices for avoiding HPPD. These are not fail-safe ways of avoiding all risks, but some common sense suggestions for minimizing risks and harm reduction.

Avoid Mixing Drugs

It is not clear what kind of effects the mix of different drugs can have. Since people frequently report that cannabis intensifies and worsens their HPPD symptoms, it may be wise to not use cannabis while tripping on other psychedelics. It is not well-known whether mixing the two poses a serious risk, but many people like to mix MDMA and LSD in a practice known as candyflipping. Some people report getting HPPD from the sensory overload of taking two drugs at once. More research on this is still necessary.

Optimize Set & Setting

Make sure you go in with a clear mind before taking a psychedelic, set the right intentions, and think about why you are taking the psychedelic. It is better to assume that ‘bad trips’ are always possible, in order to be prepared for distressing experiences. The setting is equally important, and it is worth choosing something that is not overstimulated (e.g. nature) and contains social support.


Make use of drug-testing services or products to make sure the psychedelic substance is not contaminated with Novel Psychoactive Substances (NPS).

Self-Care in the Post-Drug Phase

As mentioned earlier, neuroplasticity is heightened for one week after using psychedelics. It may be that this is an important contributing factor to developing HPPD. To avoid the risk, try to maintain a healthy lifestyle in this period. Sleep well, avoid stressors, limit your screen time, and take time to process the psychedelic experience.

Current Treatments for HPPD

The History of Ketamine

Treatments for HPPD are currently underdeveloped, but some medications can even be harmful, whereas others can make the symptoms milder. More detailed information can be found via the Perception Restoration Foundation, the Neurosensory Research Foundation, and online community support groups, such as the HPPD awareness movement.

While we do not provide medical advice, we review some of the available treatments. Please consult a medical professional before attempting any of these to treat HPPD.

Effective Medication

People are most often prescribed benzodiazepines for the treatment of HPPD. Unfortunately, benzodiazepines are highly addictive, and withdrawal symptoms include similar effects as HPPD. Therefore, these medications should be used with extreme caution. Nonetheless, people report improvements in HPPD symptoms in response to using drugs like:

Please do not take this information as medical advice! If you need treatment or have questions, consult with your doctor.

Ineffective Medication

Many drugs can make the symptoms of HPPD even worse. Let's review some of them.

Prescribed Mis-Medication

Doctors often do not know what HPPD is, and because they do not know what the symptoms are, they can often misdiagnose patients with depression or psychosis. If they prescribe SSRI antidepressants or antipsychotics (e.g. risperidone), these drugs can make HPPD worse! Beware of doctors who are not familiar with HPPD when taking prescribed medications.


Many people suffering from HPPD worsen their symptoms via self-medication and develop additional problems like alcoholism. Let’s review some of these strategies to learn how to avoid such practices.

HPPD and Alcohol

Alcohol can temporarily reduce visual hallucinations, and people with HPPD often indulge in binge-drinking to temporarily reduce their symptoms, but they tend to become worse the next day. This can typically lead to comorbid alcoholism.

HPPD and Cannabis

Cannabis can frequently worsen HPPD symptoms in a permanent manner. We do not recommend using cannabis to treat HPPD.

HPPD and Psychedelics

People who develop HPPD after using psychedelics likely have a genetic predisposition to developing such symptoms. For that reason, we strongly advise against using psychedelics if you are suffering from HPPD.

Nonetheless, some people report that they resolved HPPD symptoms by re-using psychedelics. For instance, there are Reddit reports of people who overcame their HPPD by using psilocybinketamineLSD, and ayahuasca. But caution is advised against relying on individual Reddit reports, as the majority of people report that re-using psychedelics only worsens existing HPPD symptoms. Individual reports do not represent the majority of people’s experiences, so we strongly advise against using psychedelics in this type of context. Please consult a medical professional if you require treatment.


HPPD is a condition that is often underdiagnosed or just not taken seriously. But for people who suffer from it, it is a very serious condition. Up to one-third of people using psychedelics may report some kind of lasting change in their visual experiences, but only a subset of these find them to be seriously distressing. The risk may be small, but the treatments are highly inadequate, so it is worth exercising some caution in terms of mitigating risks before taking any drugs. We do not encourage drug use, but for harm reduction purposes it may be more advisable to use plant-based versions (e.g. magic mushrooms) to avoid contamination with harmful synthetic substances. If you think you might have HPPD, we encourage you to seek help from a medical professional and seek support from online communities.

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