By Lauren Smith
Last updated: 16 September 2023 & medically reviewed by Dr. Kimberly Langdon
Hallucinogen persisting perception disorder (HPPD) is a rare but potentially long-term set of visual disturbances occurring following the use of psychedelic and or hallucinogenic drugs and causing impairment and distress. Treatment includes medication, talk therapy, and reducing anxiety and stress, which can exacerbate symptoms and may be implicated in the origin of HPPD in some users of psychedelic drugs.
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What is HPPD?
Hallucinogenic persisting perception disorder (HPPD) is the recurrence of visual hallucinations and perceptual distortions that first occurred during intoxication with hallucinogenic drugs, sometimes known as flashbacks, for months or years following the cessation of drug use. These visual disturbances, sometimes known as flashbacks, include halos around lights, trails following moving objects, afterimages, visual snow, flashes of color, geometric patterns, and misperceiving objects as too big or small.
According to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V), for a diagnosis of HPPD to be made, these visual distortions must cause clinically significant distress or impairment in important areas of functioning (social, work, etc.). They also can’t be caused by any other medical or mental health condition, such as schizophrenia.
Some literature defines two subtypes of HPPD, largely distinguished by the individual’s reaction to the flashbacks:
HPPD type I: a benign, transient, reversible experiencing of visual effects that doesn’t cause distress or impairment and may be regarded positively by hallucinogen users as a “free trip.”
HPPD type II: a chronic, irreversible, or only slowly reversible visually pervasive condition, regarded by the individual as highly distressing. It’s often comorbid with mental illness and may be caused by a combination of mental illness and psychedelic exposure. Type II most closely matches the condition as described in the DMS-V.
Some type of HPPD is estimated to affect between 4% and 4.5% of people who have used hallucinogenic drugs.
Symptoms of HPPD
Hallucinogenic persisting perception disorder is characterized by the recurrence of visual phenomena caused by psychedelic drugs for days, months, or even years after the trip. In mild forms of the disorder (HPPD Type I), these visual disturbances are transient while in more severe cases (Type II), they’re pervasive and seemingly irreversible and cause impairment and distress. Sometimes these visual disturbances are triggered by stress or anxiety.
Visual hallucinations: often of geometric figures
Altered motion perception: the illusion of movement, often in the peripheral vision
Flashes of color
Trails following objects in motion
Palinopsia: afterimages of objects no longer in sight
Halos surrounding objects
Microsopia and macrosopia: misperceiving objects as too small or too large
Floaters: specks that seem to drift in front of the eye
Visual snow: grainy, pixelated vision, like television static
Fractals: geometric figures commonly seen during trips
Acquired dyslexia and difficulty reading
These disturbances are often accompanied by other symptoms, including: 
Derealization: a sensation of being disconnected from the surrounding world
Depersonalization: a feeling of being estranged from yourself and your thoughts, of being outside your body
Causes of HPPD
LSD - the most common cause, perhaps simply because it was traditionally the most available psychedelic drug
Psilocybin (magic mushrooms)
It’s still unknown how or why these substances—which have various effects on the brain—trigger HPPD in some users. Further complicating the situation, some people develop HPPD after a single exposure to these substances, while others can use psychoactive substances for years before developing ongoing visual disturbances or never do.
The primary hypothesis about HPPD’s neurological origins is that psychoactive substances, especially LSD, can cause chronic disinhibition of visual processors in the brain.
Other researchers have suggested that psychoactive substances may cause a temporary or permanent impairment in the Lateral Geniculate Nucleus (LGN), a part of the brain, located in the thalamus, associated with visual perception pathways.
However, visual disturbances defined as HPPD also occur in people who have never used psychedelics or other drugs, especially those with anxiety disorders. HPPD symptoms can also manifest months or years after psychedelic use, throwing into question the causal link between the drug and the visual disturbances.
Another hypothesis holds that HPPD is less a drug-induced condition than a somatic symptom disorder. In somatic symptom disorders, individuals excessively focus on physical symptoms, often benign and ordinary, to the point of distress and impairment. According to this hypothesis, individuals with HPPD have simply become uncomfortably aware of normal visual phenomena and, believing they’re a result of drug use—a fear informed by popular myths of never-ending psychedelic trips—catastrophize and thus maintain their awareness of this visual noise. 
What does HPPD feel like?
Some people experience the visual phenomena of HPPD as benign. They may even regard it positively as a “free trip.” In one self-selecting survey, 60.6% of hallucinogen users reported some lingering visual effects, but 93% largely weren’t bothered by them. 
However, those with Type II find it deeply distressing and disruptive to their lives. One study found that 65% of patients with HPPD experience panic attacks and half experience major depression. Breakdowns and suicidal thoughts are common. 
In one first-hand account, a patient identified only as Greg W. describes falling “into a black hole of panic, crushing depression, terror, horror, and hell” two weeks after a bad LSD trip. He says he remains “indelibly stamped with HPPD” although, after decades, it no longer controls his life. 
In another account, YouTuber Grayson Guice described feeling like he was in a "weird dream" the morning after a bad trip on psilocybin. “I looked in the mirror and it felt like I wasn’t even in my body … I was completely depersonalized, completely derealized," he said, describing the non-visual symptoms that often accompany HPPD. 
Getting diagnosed with HPPD
HPPD has been included in the DSM, the bible of psychological diagnoses, since 1987. However, it likely remains underdiagnosed, both because patients are reluctant to seek treatment and clinicians are uninformed about it.
To be diagnosed with HPPD, you need to find a mental health professional, such as a psychiatrist or psychologist, familiar with the condition. You also need to meet the diagnostic criteria, which, as of the DSM-V, is: 
Reexperiencing one or more of the perceptual symptoms that were experienced while intoxicated with hallucinogens.
The symptoms in criteria A cause clinically significant distress or impairment in important areas of functioning such as social and occupational environments.
The symptoms cannot be attributed to an underlying medical condition and are not accounted for by another mental disorder or hypnopompic hallucinations.
Other conditions that must be ruled out for a diagnosis of HPPD to be made include: 
Brain infections (encephalitis)
Treatment for HPPD
Benzodiazepines: especially clonazepam (Klonopin); recommended only for a short period of time due to the risk of abuse and addiction
Lamotrigine: mood stabiliser
Anticonvulsants: such as gabapentin
Antipsychotics: especially risperidone. However, they may make symptoms worse in some patients.
SSRIs: may cause an initial increase in symptoms before reducing them
Calcium channel blockers
Talk therapy is also recommended, especially when HPPD is co-morbid with anxiety and depression. Therapy, especially cognitive behavioural therapy (CBT) can help patients reduce the anxiety that can make HPPD symptoms worse, redirect their attention, and improve their mood.
In one review of research, among patients who participate in treatment programs, including medication and therapy, around two in three (63.2%) had a positive outcome, with around a third of the total patients treated (29.8%) experiencing remission and another third (33.3%) attaining partial remission. 
Coping methods for HPPD
Treatment may not lead to complete recovery, and patients, especially those with Type II, must learn to cope with the visual disturbances. In many accounts, accepting the visual phenomena helps patients learn to ignore them.
Recommended coping mechanisms for living with HPPD include:
Abstinence from any drugs
Relaxation techniques: including breathing exercises, grounding, yoga, meditation
Healthy daily routine: including eating well and exercising