Trails behind moving objects, halos around lights, a kind of fine snow over everything you look at. Sometimes, weeks or months after a psychedelic experience, visual perception does not quite return to where it was. When that persists and causes distress, it is called hallucinogen persisting perception disorder, or HPPD.
It is a subject surrounded by myths, both from those who deny it and from those who present it as a guaranteed life sentence. The available evidence is limited, but it does allow a few things to be said on solid ground. This article is informational and does not replace a medical assessment.
Key takeaways
- Mild, passing visual changes after taking psychedelics are relatively common. HPPD as a disorder that causes distress is uncommon.
- The movie-style flashback, suddenly reliving the entire trip, is rare. What usually happens is specific visual disturbances.
- It is not known for certain why it happens or who it will happen to. It has been described even after a single use.
- There is no treatment backed by solid evidence. The advice most often repeated in the literature is to stop all substances, cannabis in particular, and to reduce anxiety.
- If you have persistent visual symptoms, the first step is a medical checkup to rule out other causes.
What HPPD is
The DSM-5 diagnostic manual defines it with three criteria: re-experiencing, after having stopped using, perceptual symptoms that were experienced during intoxication; that this causes significant distress or impairment; and that it is not better explained by a medical condition or by another mental disorder.
The symptoms are almost always visual:
- Visual snow: fine dots across the entire field of vision, like a badly tuned television.
- Trails behind moving objects and afterimages that are slow to disappear.
- Halos around lights and objects.
- More intense colors or flashes of color.
- Geometric shapes with your eyes closed or on smooth surfaces.
- Objects that look larger or smaller than they are.
- A sense of movement in peripheral vision.
People who have it know that what they are seeing is not real. That intact awareness is what distinguishes it from a psychotic episode.
Flashbacks and HPPD: they are not the same thing
A systematic review published in Frontiers in Psychiatry sets out the most widely used distinction between two types:
- Type I: brief, occasional episodes, often mild, that appear in the days or months that follow. Many people do not experience them as distressing. This is what is popularly called a flashback.
- Type II: persistent or highly recurrent disturbances that cannot be controlled and are usually accompanied by anxiety, low mood or depersonalization. This is the presentation that most worries those who live with it.
The image of someone who, years later, suddenly finds themselves in the middle of a trip again has little to do with what the studies describe.
How often it occurs
It is not known precisely, and that is the honest answer. Well-designed population studies are lacking.
The most frequently cited figure comes from an online survey of 2,455 people with a history of hallucinogen use. More than half had at some point noticed visual experiences of this kind while not under the influence of any substance, but only 4.2% considered them bothersome enough to think about seeking treatment. Since these were volunteers recruited on a website about drugs, the figure cannot simply be applied to people who use these substances as a whole.
What is known about the causes
Little. LSD is the substance most often associated with it, but it has also been described with psilocybin, MDMA, mescaline, cannabis and new synthetic substances. The review cited above notes that no clear relationship has been demonstrated with age at first use, frequency or quantity.
The hypotheses point to changes in the way the brain filters visual information, but none has been confirmed. What is known are factors that intensify the symptoms in people who already have them:
- Cannabis, one of the triggers most often repeated in the literature.
- Other substances, including alcohol and stimulants.
- Stress, anxiety and tiredness.
- Dark environments and the abrupt shift from light to darkness.
Anxiety deserves a separate mention. Many mild disturbances would go unnoticed if it were not for the constant attention paid to them. Monitoring your vision makes them more present, and that increases the anxiety.
How long it lasts
It varies widely. Some cases fade within weeks or months and others have been described as lasting five years or more. The literature records complete remissions without treatment, as well as persistent cases. Many people report that, with time and without using, the symptoms ease or stop bothering them even if they do not disappear entirely.
What the evidence says about treatment
Here it is important to be especially clear: there is no approved treatment and there are no high-quality controlled trials. Almost everything that is known comes from case reports and small case series.
- Benzodiazepines such as clonazepam: these have the most favorable reports, although they carry a risk of dependence and should only be used under medical supervision.
- Lamotrigine: there are several published cases with a good response.
- Antipsychotics such as risperidone: in most of the reports reviewed, they made the symptoms worse.
- SSRI antidepressants: contradictory results, with initial worsening described.
None of these medications should be taken on your own initiative. The decision belongs to a doctor who knows the case.
Medication aside, the most frequently repeated recommendations are the simplest ones: stopping all substances, treating anxiety and insomnia, and receiving a reassuring explanation of what is happening.
What to do if you have symptoms
- Stop using psychedelics, cannabis and other substances.
- Ask for a medical checkup. Similar symptoms can be due to migraine with aura or to eye or neurological problems, and there is a visual snow syndrome that appears with no connection to any substance.
- Tell the doctor what you took and when.
- Look after your sleep and cut down on caffeine.
- Avoid checking your vision at every moment.
- If there is anxiety or a sense of unreality, read anxiety or depersonalization after a trip: when to seek help.
Prevention: what can and cannot be done
No one can guarantee that it will not happen. The reasonable approach is to reduce exposure: cautious doses, plenty of time between experiences, not mixing with cannabis and, above all, not using again if you have already noticed persistent visual disturbances. Having had them is a strong reason to rethink your use, just like those we set out in who should not take psychedelics.
Support with your feet on the ground
At RILOFU we do not sell or supply substances, and we do not diagnose or treat HPPD: that is a matter for health professionals. What we can do is support the emotional side of a difficult experience and the anxiety it sometimes leaves behind.
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Sources
- The “Endless Trip” among the NPS Users: Psychopathology and Psychopharmacology in the Hallucinogen-Persisting Perception Disorder. A Systematic Review. Frontiers in Psychiatry, 2017.
- Abnormal visual experiences in individuals with histories of hallucinogen use: A web-based questionnaire. Drug and Alcohol Dependence, 2011.
- Hallucinogen Persisting Perception Disorder: Etiology, Clinical Features, and Therapeutic Perspectives. Brain Sciences, 2018.