Short answer
Hallucinogen persisting perception disorder, or HPPD, is when visual effects like trails, halos, visual snow, or color flashes continue or come back after a psychedelic has worn off. Brief, harmless flashbacks are fairly common among hallucinogen users. Persistent, distressing HPPD is much rarer, is most often linked to LSD, and appears less common in supervised clinical settings than in recreational use. Some cases improve with treatment.
Key takeaways
- HPPD comes in two flavors: brief, benign flashbacks and a persistent, distressing form.
- The DSM-5 figure often quoted is about 4.2% of hallucinogen users, but researchers say real prevalence is unknown.
- LSD is linked to far more reported cases than psilocybin.
- Clonazepam has the most consistent treatment signal so far, but the evidence is thin.
What HPPD is
Hallucinogen persisting perception disorder is a diagnosis in the DSM-5, psychiatry's official manual. It describes visual disturbances similar to those experienced during a trip that keep happening after the drug is gone, and that cause distress or get in the way of daily life.1 Common symptoms include:
- Trails or afterimages behind moving objects
- Visual snow, a static-like grain over everything
- Halos around lights
- Intensified colors or flashes of color
- Objects looking bigger or smaller than they are
- Geometric patterns, especially on plain surfaces
People with HPPD know these aren't real. That separates it from psychosis.
The two types
| Type I | Type II | |
|---|---|---|
| What it is | Brief, benign flashbacks | Persistent, pervasive disturbances |
| Course | Short-term and reversible | Long-term, slowly reversible or ongoing |
| Impact | Mild; some people find them pleasant | Can be distressing and impairing |
| Estimated frequency | Common among hallucinogen users | Uncommon |
Source: Martinotti and colleagues, 2018, and Doyle and colleagues, 2022.12
How common is HPPD with psilocybin?
Here's the honest answer: nobody knows precisely. The DSM-5 cites an estimate of about 4.2% of hallucinogen users, but reviewers point out that real prevalence is unknown and the condition is often unrecognized.1 Short-lived flashbacks are much more common than the persistent form.2
A few patterns stand out. LSD accounts for the large majority of documented cases, with psilocybin, MDMA, cannabis, and synthetic cannabinoids appearing less often.12 And HPPD appears less likely in controlled research or therapy settings than in recreational use, which reviewers attribute to screening, consistent doses, and supervision.2 In a pooled analysis of 110 volunteers given psilocybin in research studies, no lasting perceptual problems were reported.3
What might raise the risk
No risk factor has been firmly established. Limited evidence points toward unusually strong doses, frightening or dysphoric experiences, and continued use of the drug that preceded symptoms.2 Some people notice symptoms worsen with stress, fatigue, caffeine, or cannabis.
Treatment
There's no FDA-approved treatment for HPPD, and the research consists mostly of case reports and small studies. Among those, clonazepam, a benzodiazepine, has shown the most consistent benefit. Clonidine, certain anticonvulsants like lamotrigine and levetiracetam, and some other medications have shown promise in individual cases.12 Practical steps clinicians often suggest include avoiding hallucinogens and cannabis, managing stress and sleep, and getting an eye and neurological exam to rule out other causes.
If you're dealing with persistent visual changes, see a doctor and tell them about past substance use. It changes what they look for.
Common questions
Can HPPD go away?
Often, yes. Many cases, especially the milder flashback type, fade over weeks to months. The persistent form can last longer and may need treatment. Avoiding further hallucinogen and cannabis use is commonly recommended.
Is visual snow the same as HPPD?
Not exactly. Visual snow syndrome can happen in people who have never used drugs. When visual snow starts after hallucinogen use and persists, it can be part of an HPPD diagnosis. A neurologist or ophthalmologist can help sort it out.
Did clinical psilocybin trials report HPPD?
It has rarely been reported in controlled research. A 2022 scoping review concluded HPPD appears less likely in therapeutic and research settings, possibly because of careful screening, known doses, and supervision.
Sources
- Martinotti G, et al. Hallucinogen persisting perception disorder: etiology, clinical features, and therapeutic perspectives. Brain Sciences. 2018. doi.org/10.3390/brainsci8030047
- Doyle MA, et al. Hallucinogen persisting perceptual disorder: a scoping review covering frequency, risk factors, prevention and treatment. Expert Opinion on Drug Safety. 2022. doi.org/10.1080/14740338.2022.2063273
- Studerus E, et al. Acute, subacute and long-term subjective effects of psilocybin in healthy humans: a pooled analysis of experimental studies. Journal of Psychopharmacology. 2011. doi.org/10.1177/0269881110382466
This article is for education only and is not medical or legal advice. Psilocybin is a Schedule I substance under U.S. federal law. Talk with a licensed clinician before making decisions about your health. In a crisis, call or text 988.