DISCLAIMER

Very little is known about HPPD. The information in this FAQ is a combination of medical studies, information from HPPD support sites, email interviews with HPPD subjects and researchers, and speculation by the authors. All speculation is clearly identified as such. Although every attempt has been made to be accurate, some of this information will no doubt need to be corrected. If you are aware of any studies or have any information that would help make this FAQ more accurate please contact hppd@erowid.org. The authors of this FAQ are not medical doctors and no part of this FAQ should be considered medical advice.

CONTENTS

1. What is HPPD?
2. How is HPPD different from flashbacks?
3. What are the symptoms of HPPD?
4. What causes HPPD?
5. Do bad trips have anything to do with HPPD?
6. How common is HPPD?
7. How many times can I take hallucinogens before I am at risk?
8. I've taken lots of hallucinogens without problems. Am I immune?
9. Can hallucinogens cause visual problems even if I don't have HPPD?
10. Are there any warning signs I am at risk?
11. What is the medical explanation for HPPD?
12. How long does HPPD last?
13. What aggravates it?
14. Are there any support groups?
15. What are the medical treatments?
16. What are the non-medical treatments?
17. Can I still do other drugs if I have HPPD?
18. What is Palinopsia?
19. Notes & References
20. Revision History

APPENDIX A: DSM IV Entry on HPPD
APPENDIX B: References and Links

1. What is HPPD?

Hallucinogen Persisting Perception Disorder is a long-term visual disorder caused by taking hallucinogens. While sometimes referred to as "Flashbacks", it is generally agreed that this term is inappropriate for the visual disturbances most commonly experienced after psychedelic use. It is a recognised condition described in DSM IV (Diagnostic and Statistical Manual of Mental Disorders) under Diagnostic Code: 292.89. The DSM is the standard manual for mental disorders used by psychologists and psychiatrists in the United States. In the DSM III, HPPD was referred to as Post Hallucinogen Perception Disorder (PHPD) and this phrase is often still used. In the 1960s and 1970s, HPPD was often included under the umbrella term "flashbacks". Although flashbacks and persisting perceptual disorders are distinct problems, the two may be associated. Unlike flashbacks, HPPD is most often characterized by continual visual interference rather than a series of acute attacks.

In mild cases, subjects occasionally experience minor visual distortions. In its most severe forms, subjects have a full range of LSD-like visual effects such as tracers, color trails, and distorted object sizes on an ongoing basis. A more complete list of symptoms can be found in the Symptoms section of this FAQ. Severe HPPD is very debilitating and subjects often seek psychiatric help.

Medically, there are three conditions which define HPPD:

1. Subjects experience drug-like sensory disturbances while not under the influence of any drugs.
2. The disturbances interfere with work, school, social settings, or other areas.
3. There are no other physical or mental conditions that account for the disturbances (lesions, visual epilepsy, schizophrenia, dementia, etc.)

The complete DSM IV criteria can be found in Appendix A of this FAQ. HPPD is a psychiatric diagnosis (the DSM IV is a manual for psychiatry) and is different from the more neutral medical term "palinopsia". Palinopsia is a technical term used in opthamology to describe abnormally prolonged visual afterimages, especially on moving targets or high contrast objects, or 'trails'. For more information see the section on palinopsia.

2. How is HPPD different from flashbacks?

Flashbacks are normally thought of as occasional reoccurences of a drug-like state. HPPD differs in two ways:

1. HPPD is recurrent or ongoing.
2. HPPD is purely visual. HPPD subjects have full reality testing, meaning that they are aware that what they are seeing is not real.

Flashbacks consist of acute events where the individual experiences significant alterations in their thoughts, feelings, and/or perceptions which are reminiscent of earlier experiences. Other characteristics of flashbacks can include resurfaced memories, depersonalization or extreme detachment, altered sense of reality, re-experiencing thought-loops similar to a previous experience, visions of former experiences or traumatic events, anxiety or panic, and the like.

Flashbacks are associated with traumatic experiences and are generally considered a symptom of Post Traumatic Stress Disorder. Flashbacks are also known to be caused by non-psychoactive drug related experiences. Any type of powerful experience can potentially lead to memories and feelings from that experience intruding into one's thinking. HPPD is not necessarily associated with any traumatic event and does not usually elicit acute panic attacks, but may accompany them.

3. What are the symptoms of HPPD?

HPPD subjects experience a wide range of visual disturbances. These disturbances are the result of changes in the way that the brain processes visual information.

It is important to realize that many of these visual disturbances are present to some degree in healthy people. For example, most people will see points of light, "floaters", and other visual effects if they stare at a blue sky or brightly lit white surface for several minutes. Everybody sees shapes in clouds or see halos around lights at night. These things are normal.

What differentiates the medical condition of HPPD from normal visual 'noise' is the severity of these effects. HPPD subjects have these effects with sufficient frequency and severity that it interferes with their ability to function in their daily lives.

HPPD symptoms vary widely in severity and frequency. In mild cases, HPPD is little more then an occasional annoyance. In severe cases subjects report a wide range of the symptoms listed below on an ongoing basis.

Partial List of HPPD Symptoms

Afterimages	After looking at an object for a while and then looking away, a positive or negative image of the object remains visible.
Color Confusion	It is difficult to tell colors apart. Colors may appear to change over time. Example: a red sweater may turn yellow, or black text in a book may turn bright green.
Reduced Color Discrimination	Some subjects report a reduction in the brightness or fidelity of colors, sometimes making it harder to tell similar colors apart.
Difficulty Reading	Text may sway back and forth. Letters leave positive and negative after-images. Letters may vanish into an "alphabet soup".
Flashes of color	Subjects may see bright lights, flashes, or sheets of color that appear and disappear.
Geometric Patterns	Subjects see geometric patterns and shapes. Example: leaves in a tree may form patterns.
Halos around objects	Objects appear to have halos that extend for some distance around their edges.
Images within Images	Subjects see faces or other complex images where none exist. Example: a hardwood floor may appear to be made out of faces.
Movement	Stationary objects appear to sway back and forth or slide across the floor. This is most common in the peripheral vision.
Size Distortions	Objects temporarily seem to be smaller or larger then they actually are and then return to their normal sizes.
Static	Subjects see static over monochrome surfaces. This is especially noticeable at night. Example: in a totally dark room it may look like there is a TV set turned on broadcasting static.

4. What causes HPPD?

HPPD is defined to be caused by taking 'hallucinogenic' drugs, but its root cause is poorly understood. Dr. Henry Abraham ( a leading researcher in this area) believes that HPPD may be partially genetic though he says that he knows of no published evidence [personal communication - tacovan]. It seems to be most commonly related to LSD use, perhaps because LSD is the most common hallucinogen, but there are also reports of HPPD being caused by other psychedelics such as mushrooms, MDMA, MDA, 2CT7, 5-MEO-DiPT, etc. There are a few people who have HPPD-like symptoms who have never taken any drugs, but the definition of Hallucinogen Persisting Perceptual Disorder does not include these individuals.

Based on anecdotal evidence HPPD subjects fall into two broad categories. A large percentage (probably the majority) got HPPD fairly early in their experimentation with hallucinogens. They also seem to get fairly severe cases of it. Dr. Abraham also confirms that this appears to be the case and says this is one of the reasons he believes HPPD to have genetic origins. For further information see (Abraham HD. Visual phenomenology of the LSD flashback. Arch Gen Psychiatry; 40: 884-889, 1983)

The second set of users are long-term drug users who got HPPD well into their experimentation with drugs. These people report that they get HPPD from a wide variety of drugs. Since most long-term users of multiple drugs also use LSD, it is hard to really distinguish what drugs are responsible for HPPD in these cases. However, there are a numerous reports of long-term drug users who had strong trips on non-LSD drugs which led immediately into HPPD symptoms.

Erowid has received over a dozen reports from ecstasy users who have reported significant visual disruptions after taking ecstasy that lasted for six or more weeks. (See MDMA Aftereffects)

5. Do bad trips have anything to do with HPPD?

A large percentage of HPPD subjects experienced bad trips. However, some subjects have had nothing but positive experiences and still got HPPD. Bad trips are far more likely to lead to Post Traumatic Stress Disorder, which is associated with an increase in negative aftereffects from psychoactive experiences. Since the mechanism for what causes HPPD is not yet known, it is difficult to know what factors might increase or decrease the chance of experiencing long term visual changes.

Speculation: Many people have had bad trips and not developed HPPD. However, most people who have HPPD have had bad trips. Bad trips may be a warning sign of increased HPPD risk, but they do not directly cause HPPD.

Since part of the medical definition of HPPD is how the visual changes affect one's life, the definition necessarily involves how the subject feels about the changes. It seems likely that those who had a severe traumatic experience while under the influence of ecstasy, LSD, or other psychoactive may find the experience of lasting visual changes more emotionally troubling.

6. How common is HPPD?

No large-scale studies have been done, and so there is no definitive answer to this. Also, even the small amount of lab research which has been done has not been reproduced and verified by unrelated labs. It is likely that HPPD is under-reported because so few people in the medical community know what it is. Severe HPPD seems to be very rare although Dr. Abraham estimates the number may be as high as 1-5% of LSD users. This is his best guess based on his research experiences and the small studies which have been done, but the epedemiological studies to verify this have not been attempted.

In ongoing research in collaboration with Erowid, Matthew Baggott and colleagues from University of California Berkeley found that HPPD-like symptoms occurred in 4.1% of participants (107 of 2,679) in a web-based survey of hallucinogen users. These 107 people reported psychedelic-related visual problems serious enough that they considered seeking professional help. Sixteen of the 107 had actually sought help and two had been diagnosed with HPPD. These numbers may overestimate how common HPPD-like visuals are, since people with visual problems may have been more interested than other people in completing the questionnaire. 2,679 people filled out the questionnaire out of 16,192 who viewed the study information. Depending on one's assumptions, these numbers can be used to make higher and lower estimates of how common HPPD is. The higher estimate is 4.1%, as detailed above. The lower estimate would be 0.12% (two confirmed cases out of 16,192 people looking at the questionnaire). Both of these estimates are uncertain and require assumptions that might be incorrect. What is more certain is that many people have drug-free visual experiences that they believe relate to past drug use.

Outside of that survey, anecdotal reports to Erowid suggest it is unlikely that there are as many as 5% of those who have ever used LSD would have clinically-significant symptoms reaching the level of HPPD, meaning people for whom visual disturbances create problems in their lives. While it is very likely Erowid's sample is biased, the 1-5% number cited by Abraham likely include sub-clinical (meaning not life-disrupting) levels of lasting visual effects.

Other guesses about the prevelance of all sub-clinical (non life disrupting) visual disturbances in psychedelic users are much higher. Unfortunately because there have been no large-scale studies, these estimates should not be considered reliable. Numbers vary widely and range from 5% all the way to 75% of all psychedelic users. Dr. Abraham estimates this number at 40%. Some references suggest that as many as "30 to 60% of heavy users experience [visual changes] in some form or another." (Buzzed first edition, pg 78. Kuhn, Swartzwelder, Wilson 1998)

In 2016, Halpern et al. re-summarized what we said here and cited Erowid's survey. They describe the prevalence of HPPD with:

Data do not permit us to estimate, even crudely, HPPD's prevalence according to DSM-V or ICD-10 criteria. Although millions of doses of hallucinogens were consumed by millions of individuals since the 1960s (SAMHSA 2011), few large HPPD case series were reported. Horowitz (1969), Cohen (1960, 1977) estimate the incidence of Type 1 HPPD in a population of regular hallucinogen users in the 1960-1970s as 1:20. Type 2 HPPD, if it exists as a reliable and distinct entity, appears to be very rare (Hermle et al. 2008, 2015; Holland and Passie 2011). Grinspoon and Bakalar (1997) estimate that Type 2 HPPD occurs in 1 of 50,000 hallucinogen users. Baggott et al. (2011) collected data online in a Web-based questionnaire from 2455 individuals reporting visual experiences while drug-free that resembled a past hallucinogen intoxication. Most of these experiences were simple, non-disturbing "flashbacks", while 4.2 % found these visual phenomena significant enough to at least contemplate seeking treatment. [Halpern et al. 2016]

Other studies have shown that some HPPD-free LSD users may experience measurable ongoing visual disturbances, yet be unaware of these changes. See here for more information.

7. How many times can I take hallucinogens before I am at risk?

Although many users of hallucinogens may experience minor visual changes, the huge majority will never develop HPPD. Many people have taken hallucinogens hundreds of times and report no ill effects.

However, some people with severe HPPD got it after their first trip. From the evidence so far, it appears that if you are prone to HPPD, then you have a good chance of getting it after only a few experiences. This is based on informal surveys of people on HPPD discussion forums and a handful of published case reports. Some of the published papers suggest that there is evidence that some people are genetically more likely to get HPPD, but we have been unable to find the references which describe this.

Dr. Abraham (the creator of the term HPPD and leading researcher into this phenomenon) dramatically describes his negative view of LSD use: "using LSD is like playing Russian roulette, but using a chemical instead of bullets".

8. I've taken lots of hallucinogens without problems. Am I immune?

Long term drug users are not immune to HPPD. There are people who have taken LSD and other hallucinogens hundreds of times without any problems. However, a fair number of HPPD subjects got HPPD after extensive use of hallucinogenic drugs.

There is some anecdotal evidence that long term hallucinogen users are more likely to experience some of the warning signs of HPPD, even if they never experience full blown HPPD.

As with many types of toxicity, the negative outcomes are related most to peak dose-exposure and the specifics of the drug(s). It might be, for instance, that one's risk of HPPD could be increased by later age, combination with other drugs, changed liver enzyme production, etc. There is nothing but speculation at this point. Most LSD users do not experience effects they consider problematic, but there are individuals who have reported unpleasant lasting visual effects after having previously taken LSD dozens of times.

9. Can hallucinogens cause visual problems even if I don't have HPPD?

There is evidence that LSD, MDMA, and other hallucinogens can produce visual problems even in people who do not have HPPD. So far, experiments have not been conducted with drugs other than LSD. Dr. Henry Abraham, the leading researcher on the topic of HPPD (and the originator of the term), did two experiments on LSD-related visual disorders. In both experiments, he used three groups of subjects. The comparison or 'control' group had never taken LSD. The second group consisted of former LSD users who had never experienced visual problems and who said they hadn't taken LSD in a long time. The final group consisted of LSD users who reported HPPD symptoms.

The first test measured the ability of the groups to distinguish colors. The control group scored the best, the former LSD users fell in the middle, and the HPPD group scored the worst. The results were statistically significant with a P < 0.001, which theoretically means that there was less than 1 in 1000 chance that the measured differences were caused by random chance. [Abstract]

The second test measured the ability of each group to distinguish light flicker. A light was rapidly strobed on and off. Above a certain frequency subjects perceived the flashing light to be on continuously. Again, the control group performed best, the former LSD users fell in the middle, and the HPPD subjects scored the worst. The results were again statistically significant (P<0.001). [Abstract]

These experiments seem to show that even HPPD-free LSD users may be experiencing long-term changes in their vision. It is not known why these changes are so distracting to people with HPPD while not being bothersome to other LSD users. It is very important to note, however, that not much research has been done in this area and these results have not been confirmed by other research.

Speculation: These results are difficult to explain. They would seem to point to a slow degradation in perception caused by LSD. HPPD seems to have very rapid onset in many cases, often after very few LSD experiences. It would be interesting to see if the strength of distortions could be correlated to total LSD experiences. It would also be interesting to do longitudinal studies of current LSD users to see how their perceptions change. There is a PhD thesis in the making for somebody!

10. Are there any warning signs that I am at risk?

Many of the symptoms of HPPD are also present in normal people. Just as HPPD can be made worse by dwelling or obsessing on the symptoms, perfectly healthy people who worry too much about HPPD risk may become annoyed by visual symtoms which are actually fairly normal. Monitoring yourself for HPPD warning signs may cause a lot of unnecessary stress and worry.

Many HPPD subjects got HPPD after an early hallucinogen experience. It may even have been their first. They had no warning signs.

Longer term drug users are more likely to have slower onset. Many of these people report that they ignored minor symptoms such as visual disturbances at night, mild "flashbacks", reduced color sensitivity, mild tracers when they were tired, etc., yet continued to use the problem drugs until the symptoms became too distracting.

Speculation: Given the high number of HPPD subjects who got HPPD early on, any hallucinogen experimentation carries some risk. Clearly there is no way to eliminate the risk, though limiting dosage on early trips and stopping at early signs of trouble are reasonable precautions.

11. What is the medical explanation for HPPD?

A high proportion of HPPD subjects got HPPD very early in their experimentation with LSD (or other hallucinogens). This supports the theory that some people have a genetic predisposition to HPPD.

Genetic or not, HPPD is a measurable physical problem with the brain. Brain scans of HPPD subjects show that there are regions of significantly elevated activity. HPPD subjects also perform worse on a few visual tests (see here):

1. Reduced sensitivity (HPPD subjects perceive a strobing light as being a continuous light at much lower frequencies then control subjects).
2. Reduced ability to discriminate between colors.

There is an excellent paper on LSD visual effects which includes a possible explanation for HPPD in the Rhodium archive.

According to this paper, the visual system in the brain has six different layers which detect different types of visual stimulus (horizontal bars excite one layer, vertical bars excite a different layer, for example). These different layers work together to process information from your eyes and pick out important details for your attention.

The amount of attention your brain pays to the signals from the various layers is based on the strength of the signal from those neurons. One theory of HPPD is that the neurons in some of these layers start overreacting to stimuli. The result is that HPPD subjects become very sensitive to things that they would normally not notice. The layers fail to filter out some of the 'noise' in the lower visual systems and the higher, more meaning- and pattern- oriented layers in the visual system interpret the incoming signals as useful data and send the signals on further into the brain and conscious mind.

For example, the edge detection systems may find too many edges resulting in halos around objects. Coordination problems between layers result in processing happening out of sync or time-delayed, resulting in tracers. Motion detection systems may cause things to look like they are moving when they are not. Face and pattern recognition area may see shapes that do not exist in complex backgrounds.

11. How long does HPPD last?

Many subjects report that their HPPD eventually gets better or completely disappears over the course of weeks, months, or years. Other subjects have had it for 10 years or longer. Generally, medically diagnosed HPPD seems to last at least a couple of years.

HPPD is a serious long-term illness and there is a chance it may not ever go away. Many subjects have no choice but to learn to live with it. If you have HPPD you should seriously consider joining an online community to discuss the medical issues and talk to others about their experiences in dealing with it. You may also want to consider medical help although results are mixed.

12. What aggravates HPPD?

Most subjects find that their symptoms vary. Generally distortions are made worse by:

1. Obsessing about HPPD symptoms (by looking at blank walls for example)
2. Fatigue
3. Alcohol, Cannabis, Psychedelics, or other drugs
4. Sudden entry into dark or light environments
5. Stress
6. Some antidepressants and other psychiatric medications (such as Risperidone)

13. Are there any support groups?

There is an excellent HPPD group at HPPD Online and a nearly inactive one at http://www.stormloader.com/hppd. For those suffering from unwanted visual symptoms, wondering if they might have HPPD, or just wanting to discuss it, these discussion groups are an excellent source of information. These forums often discuss information on treatments and advice on how to cope.

14. What are the medical treatments?

It is beyond the scope of this FAQ to provide specific medical advice. There are medical treatments available that seem to have helped some subjects.

HPPD is very difficult to treat. Most doctors and psychiatrists know nothing about it. Because of the relationship to illegal drugs, many patients receive very little sympathy from medical professionals. Some 'doctors' even go so far as to believe that HPPD and other long term problems are appropriate punishment for experimenting with proscribed drugs.¹ If you have HPPD you should try to find a qualified physicician or psychiatrist with whom you are comfortable, who has experience with HPPD.

There are a number of drugs that are used to treat HPPD. Unfortunately they need many months to work, are often not very effective, and may have serious side effects. One of the more common prescriptions is for benzodiazepines such as Clonazepam (Klonopin) or Alprazolam. Other medications have been used, including clonidine, but there is no consensus on best treatments and some medications worsen the symptoms.

Anti-psychotics such as Risperidone are sometimes given but should be avoided since they can make HPPD much worse.^{2, 3} If you are prescribed medication for your HPPD you may want to ask online to see what other people have experienced with them.

Some herbs and supplements are used by some HPPD sufferers to help alleviate the symptoms, with varying degrees of success. Some people report success with herbal remedies such as St. Johns Wort or Bach Flower Remedies.

The lack of effective medical treatments means that many people simply have to learn how to cope with HPPD. Some users find that counselling or therapy can be useful in reducing the impact of the visual effects on their life.

15. What are the non-medical treatments?

There are excellent online support groups that will give you advice and help you cope. Some report that meditation helps reduce the severity of the symptoms and associated emotional distress. Wearing sunglasses during bright days helps some people avoid sudden changes in brightness. Other suggestions, like those from the experienced writers at HPPD Online, include avoiding caffeine, relaxing, taking a warm bath, and trying not to dwell or worry about the symptoms.

16. Can I still do other drugs if I have HPPD?

Most HPPD subjects swear off recreational drugs entirely. A minority of HPPD-sufferers being able to continue using cannabis and other psychoactive drugs without a strong visual element (pain-killers for example). There is currently very little reliable information about this and it is likely that every individual's reaction is different. Many HPPD sufferers report they are able to consume alcohol weeks or months after their HPPD events without making their HPDD situation worse.

Especially with severe HPPD cases, every new drug or strong mind-altering experience needs to be approached carefully. Many with moderate to mild HPPD report that, over time, they are able to include cannabis, MDMA, and even psychedelics in their lives without triggering long lastingt anxiety or other negative symptoms of HPPD. The closer in time to the initial triggering event, the more likely people are to report that the cannabis/psychedelics make their HPPD worse.

Benzodiazepines and Abilify-type anti-psychotics are said to reduce HPPD symptoms across the board for most (but not all) HPPD sufferers.

If you have any information, feel free to share it with us at hppd@erowid.org or submit an experience to Erowid's Experience Vaults.

17. What is Palinopsia?

Palinopsia, occasionally spelled palinopia, is a common symptom of HPPD. It is a medical term used by opthamologists (eye doctors) to describe abnormally prolonged visual afterimages, especially on moving targets or high contrast objects. The effects are often called 'trails'. It is a perceptual distortion where a visual image persists after removal of the stimulus. Where HPPD diagnosis requires previous use of hallucinogens, palinopsia is not tied to a particular cause and has been reportedly caused by a variety of medications, such as clomid, risperidone, nefazodone, mirtazapine, and others. It is also sometimes caused by psychedelics and is also known to be caused by physical brain trauma or disease.

It is different from HPPD because HPPD is a psychiatric diagnosis with historical and medical ties to the much more cognitive (mind) focused concept of 'flashback'. HPPD can also encompass a very wide range of visual symptoms and its diagnosis requires that the visual problems interfere significantly with the sufferer's lifestyle. Palinopsia is much more simply the symptom of seeing after images or trails. Cases are also reported where there is no direct cause known: "Palinopsia and related visual symptoms can occur in otherwise healthy individuals and in patients with disease apparently confined to the eye or the optic nerve." (Pomeranz HD 200)

An article in a newsletter (International Drug Therapy) by a Dr. Frank J. Ayd Jr. (Sept. 2000) says "the underlying cause of palinopsia is a structural lesion of the posterior portions of the cerebral hemispheres" but it appears too early to positively identify the mechanistic cause for all types of palinopsia. What Dr Ayd's findings tell us about lesions is not exactly clear.

Palinopsia has been treated successfully with some medications, but this is an area that is not well studied or understood. For more information about palinopsia, try searching at Google or Pub Med.

Notes & References

1. Medical Disdain: Erowid has received several reports from people who have been treated badly by nurses and doctors in emergency rooms and in clinics because of the moral disapproval of experimentation with psychedelics. Although the medical oath should preclude doctors from giving worse care to individuals on the basis of disdain for their life choices, this is a reality that users seeking treatment for problems may need to face when choosing a doctor or clinic.
2. Risperidone 1: LSD-like panic from risperidone in post-LSD visual disorder. Abraham HD, Mamen A J Clin Psychopharmacol, 1996; 16(3):238-41. (Abstract)
3. Risperidone 2: Posthallucinogen-like visual illusions (palinopsia) with risperidone in a patient without previous hallucinogen exposure: possible relation to serotonin 5HT2a receptor blockade. Lauterbach EC, Abdelhamid A, Annandale JB Pharmacopsychiatry, 2000; 33(1):38-41. (Abstract)
   
4. A chronic impairment of colour vision in users of LSD. Abraham HD Br J Psychiatry, 1982; 140:518-20. (Abstract)


5. LSD-induced Hallucinogen Persisting Perception Disorder treated with clonazepam: two case reports. Lerner AG, Skladman I, Kodesh A, Sigal M, Shufman E, Isr J Psychiatry Relat Sci, 2001; 38(2):133-6. (Abstract)


6. Post-LSD Hallucinosis Is Associated With Decrease In Flicker-Fusion Sensitivities. Van Toi V, Abraham H, Bursac N, Investigative Ophthalmology and Visual Science (supp), 1996; 37(3):3300. (Abstract)

Revision History

• 1.2 Sep 1 2018 - erowid : Updated "How Common is HPPD?" section, adding quote from Halpern et al 2016.
• 1.1 Apr 18, 2008 - erowid : Updated "How Common is HPPD?" section based on M. Baggott survey results.
• 1.01 November 20, 2001 - erowid : Changes suggested by erowid reviewers.
• 1.0 November 2001 - tacovan & erowid
• 0.5 October 2001 - tacovan primary author

[ Back to HPPD Vault ] * [ Back to Psychoactives & Health Vault ]

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APPENDIX A: DSM IV ENTRY FOR HPPD

Hallucinogen Persisting Perception Disorder

Diagnostic Code: 292.89

The essential feature of Hallucinogen Persisting Perception Disorder (Flashbacks) is the transient recurrence of disturbances in perception that are reminiscent of those experienced during one or more earlier Hallucinogen Intoxications. The person must have had no recent Hallucinogen Intoxication and must show no current drug toxicity (Criterion A). This re-experiencing of perceptual symptoms causes clinically significant distress or impairment in social, occupational, or other important areas of functioning (Criterion B). The symptoms are not due to a general medical condition (e.g., anatomical lesions and infections of the brain or visual epilepsies) and are not better accounted for by another mental disorder (e.g., delirium, dementia, or Schizophrenia) or by hypnopompic hallucinations (Criterion C). The perceptual disturbances may include geometric forms, peripheral field images, flashes of color, intensified colors, trailing images (images left suspended in the path of a moving object as seen in stroboscopic photography), perceptions of entire objects, afterimages (a same-colored or complementary-colored "shadow" of an object remaining after the removal of the object), halos around objects, macropsia, and micropsia. The abnormal perceptions that are associated with Hallucinogen Persisting Perception Disorder occur episodically and may be self-induced (e.g., by thinking about them) or triggered by entry into a dark environment, various drugs, anxiety or fatigue or other stressors. The episodes may abate after several months, but many persons report persisting episodes for 5 years or longer. Reality testing remains intact (i.e., the person realizes that the perception is a drug effect and does not represent external reality). In contrast, if the person has a delusional interpretation concerning the etiology of the perceptual disturbance, the appropriate diagnosis would be Psychotic Disorder Not Otherwise Specified.

Diagnostic criteria for Hallucinogen Persisting Perception Disorder

1. The re-experiencing, following cessation of use of a hallucinogen, of one or more of the perceptual symptoms that were experienced while intoxicated with the hallucinogen (e.g., geometric hallucinations, false perceptions of movement in the peripheral visual fields, flashes of colors, intensified colors, trails of images of moving objects, positive afterimages, halos around objects, macropsia, and micropsia.
2. The symptoms in Criterion A cause clinically significant distress or impairment in social, occupational, or other important areas of functioning.
3. The symptoms are not due to a general medical condition (e.g., anatomical lesions and infections of the brain, visual epilepsies) and are not better accounted for another mental disorder (e.g., delirium, dementia, Schizophrenia) or hypnopompic hallucinations.

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APPENDIX B. HPPD Links

• Stormloader HPPD Site (excellent discussion groups)
• HPPD Forum - Another good HPPD web site
• Erowid HPPD Vault
• A Hypothesis of the Mechanisms Underlying Visual Distortions Caused by Psychedelic Drugs (author unknown)

Revision History #

• v1.12 - Mar 12, 2019 - Erowid - Updated #OtherDrugs section based on visitor comments.
• v1.11 - Nov 26, 2009 - Erowid - Updated support paragraph, added hppdonline.
• v1.1 - Apr 18, 2008 - Erowid - Corrected minor errors.
• v1.0 - Nov 20, 2001 - Erowid - Initial publication by Tacovan and Erowid.