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Hallucinogen persisting perception disorder
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Hallucinogen Persisting Perception Disorder or HPPD is a disorder characterized by a continual presence of visual disturbances that are reminiscent of those generated by the ingestion of hallucinogenic substances. Previous use of hallucinogens is needed, though not sufficient, for diagnosing someone with the disorder. For an individual to be diagnosed with HPPD, the symptoms cannot be due to another medical condition.
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Hallucinogen Persisting Perception Disorder or HPPD is a disorder characterized by a continual presence of visual disturbances that are reminiscent of those generated by the ingestion of hallucinogenic substances. Previous use of hallucinogens is needed, though not sufficient, for diagnosing someone with the disorder. For an individual to be diagnosed with HPPD, the symptoms cannot be due to another medical condition. HPPD is distinct from flashbacks by reason of its relative permanence; while flashbacks are transient, HPPD is persistent. HPPD is a DSM-IV diagnosis with diagnostic code 292.89.
Symptoms
There are a number of perceptual changes that can accompany HPPD. Typical symptoms of the disorder include: halos surrounding objects, trails following objects in motion, difficulty distinguishing between colors, apparent shifts in the hue of a given item, the illusion of movement in a static setting, air assuming a grainy or textured quality (visual snow or static, by popular description), distortions in the dimensions of a perceived object, and a heightened awareness of floaters. The visual alterations experienced by those with HPPD are not homogeneous and there appear to be individual differences in both the number and intensity of symptoms.
Visual aberrations can occur periodically in healthy individuals – e.g. afterimages after staring at a light, noticing floaters inside the eye, or seeing specks of light in a darkened room. However, in people with HPPD, symptoms are typically so severe that the individual cannot ignore them and HPPD is associated with new visual disturbances. It does not appear to merely increase those already in existence.
It also should be noted that the visuals do not constitute true hallucinations in the clinical sense of the word; people with HPPD recognize the visuals to be illusory, or pseudohallucinations, and thus demonstrate no inability to determine what is real (in contrast to, e.g., Schizophrenia).
Prevalence of HPPD
It is not known how frequently people develop HPPD. In their review article, John Halpern and Harrison Pope write that "the data do not permit us to estimate, even crudely, the prevalence of ‘strict’ HPPD." These authors noted that they had not encountered it in their evaluation of 500 Native American Church members who had taken the hallucinogenic cactus peyote on at least 100 occasions. In a presentation of preliminary results from ongoing research, 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 people reported visual problems after drug use that were serious enough that they considered seeking professional help. This number may over-estimate the prevalence of HPPD since people with visual problems may have been more interested in completing the researchers' questionnaire. The authors reported that 16,192 people viewed the study information but did not complete the questionnaire. If all these people had used hallucinogens without developing visual problems, then the prevalence of serious visual problems in this larger group would be 0.66%. Since these people were not formally diagnosed in person (and may have had visual problems caused by other disorders), this number may provide a reasonable upper limit on the prevalence of HPPD.
It is possible the prevalence of HPPD has been underestimated by authorities because many people with visual problems relating to drug use either do not seek treatment or, when they do seek treatment, do not admit to having used illicit drugs. In the sample of Baggott, only 16 of the 107 people with possible HPPD had sought help and two of these people had been diagnosed with HPPD. Thus, it may be that HPPD occurs more often than is detected by the health care system.
Causes
The cause(s) of HPPD are not yet known. It is very clear that most hallucinogen users do not develop HPPD . This suggests there may be unknown factors that make a small subset of individuals vulnerable. It is possible that HPPD may have both neurological and psychological components with the contributions of both aspects varying from case to case. The most current reseach indicates that HPPD symptoms are caused by abnormalities in CNS function and have no retinal origin.
Some people have suggested that HPPD may be similar to posttraumatic stress disorder and involve vivid reliving of intensely unpleasant experiences. However, many (if not most) published cases of HPPD do not appear to involve a severe 'bad trip' before the onset of symptoms. In addition, a number of psychiatric medications have been noted to cause visual changes similar to HPPD. This seems to be evidence that the symptoms are not related to a bad trip but have an underlying pharmacological or neurological mechanism.
Another theory is that HPPD induces a hyper-sensitivity to ordinary visual phenomena that exist in normal people but are typically ignored. Under this interpretation, the disorder transforms mundane perceptual effects into a source of distress. For this reason, some have argued that HPPD should be considered a “disinhibition of visual processing” (Psychedelic Drugs, Abraham, et al, pg. 1548). However, this theory does not appear to explain the symptoms that are uncommon in healthy people (e.g., trails behind moving objects). Many people with HPPD report that they had not experienced the particular visual phenomena of HPPD prior to its onset.
In some cases, HPPD appears to have a sudden onset after a single drug experience, strongly suggesting the drug played a direct role in triggering symptoms. But in other cases, people report gradual worsening of symptoms with ongoing drug use.
Drugs that have been associated with HPPD include LSD, 2C-I, 5-MeO-DIPT , MDMA, Psilocybin, Mescaline, deliriants (such as Diphenhydramine or Scopolamine) and high-dose usage of dextromethorphan.
Co-existing problems
The visual problems of HPPD can occur along with other mental ailments. Of these, the most prominent are anxiety, panic attacks, depersonalization disorder, and depression. In the sample of Baggott and colleagues, hallucinogen users with persisting and severe visual problems were significantly more likely to report anxiety and depression diagnoses than hallucinogen users without serious visual problems. For example, 25.9% of hallucinogen users with visual problems reported current or past diagnosis of depression. While it is difficult, if not impossible, to establish a clear relationship between the visual and mental symptoms, those with HPPD often testify that a connection indeed exists. For example, anxiety can cause the visuals to become more prominent and vice-versa. Anecdotal wisdom thus maintains that there is a synergistic link between the two. However, there appear to be people with 'pure' cases of HPPD in which no other disorders co-exist.
Treatment
As of yet, there is no cure available for HPPD. The principal treatments seek to reduce symptoms and distress without treating underlying causes. Benzodiazepines including clonazepam (Klonopin),
diazepam (Valium) and alprazolam (Xanax) are prescribed with a fair amount of success. Some medications have been contraindicated on the basis of their effects on HPPD or the concurrent mental issues. The atypical antipsychotic Risperidone is reported to worsen symptoms of HPPD during the drug's duration in some people.
Those with HPPD are often advised to discontinue all drug use, many of which are thought to increase visuals in the short-term. There are also less concrete factors that may be generally detrimental to those with HPPD. For example, sleep deprivation and stress are thought to increase HPPD symptoms. However, no published studies have investigated whether any of these recommendations are helpful.
There is no universal time course of HPPD recovery. The adverse psychological effects of HPPD (assuming these effects appeared at all) appear to lessen more rapidly than the visuals; quality of life often returns as a person adjusts. Recovery may be facilitated by a psychological habituation to the visuals, which, in effect, reduces the victim’s inclination to attend to and react negatively to them. The deleterious consequences of the visuals can therefore be reduced even if the HPPD does not disappear.
There is currently little reliable information on how often people fully recover from HPPD. There have been reports of HPPD victims having normal perception totally return. The small number of cases of HPPD that have been studied in depth make it difficult to determine how often and under what conditions the visual symptoms of HPPD resolve.
Other disorders with similar symptoms
It must be emphasized that individuals without HPPD will sometimes notice visual abnormalities. These include floaters (material floating in the eye fluid that appears as black/dark objects floating in front of the eyes and are particularly visible when looking at the bright sky or on a white wall). Likewise, bright lights in an otherwise dark environment may generate trails and halos. Most people don't notice these effects, because they are so used to them. A person fearful of having acquired HPPD may be much more conscious about any visual disturbance, including those that are normal. In addition, visual problems can be caused by brain infections or lesions, epilepsy, and a number of mental disorders (e.g., delirium, dementia, schizophrenia, Parkinson's disease). For an individual to be diagnosed with HPPD, these other potential causes must be ruled out.
See also
External links
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