Hallucinogen persisting perception disorder (HPPD) is a rare medical condition that can cause visual disturbances (sometimes called flashbacks) if you’ve taken hallucinogenic drugs in the past. With HPPD, you re-experience the visual aspects of a drug trip, even though you haven’t taken any kind of substance in months or even years.
How rare is it?
Among those who’ve taken hallucinogenic drugs, only 4% to 4.5% get HPPD. Getting an accurate count of HPPD cases is difficult because there haven't been many population studies about it.
Another thing that complicates estimating the number of cases is that HPPD often looks like other conditions, including:
Migraine aura without headache, an uncommon type of migraine without head pain that can make you see spots, zigzags, or flashes. It can even cause sight loss for a short time.
Focal epilepsy, a condition that affects the nervous system, causing seizures on one half of your brain that lead to hallucinations, flashing bright lights, or other visual changes.
Visual snow syndrome (VSS), a disorder that makes you see static or flickering dots in your vision.
Narcolepsy-cataplexy syndrome, a rare type of sleep disorder that can cause hallucinations just before you fall asleep or when you wake up.
Hallucinogen Persisting Perception Disorder Types
HPPD has two types. Both involve visual disturbances that can last from minutes to years. Both tend to come with an anxious feeling with each episode. But the types are different in the way they come about, how long they last, and how severe they are.
HPPD type 1
HPPD type 1, also called “benign flashback type,” involves shorter, random “flashbacks.”
With HPPD type 1, you’re more likely to have a “warning aura” before your episode. This is a feeling of self-detachment (numbness to your emotions) or confused state that happens before you start having symptoms.
The episodes are usually milder than type 2 episodes. You may feel a vague sense of unpleasantness, but the episode doesn’t typically make you lose control or function. The symptoms that happen are reversible. Episodes of type 1 HPPD don’t come back as often as type 2 episodes typically do.
HPPD type 2
HPPD type 2 is more chronic, long-term, and severe. It can cause ongoing problems with your vision, and come back again and again. The hallucinations are typically long, and can come and go over the course of months or years. You may have a mix of mild and more intense episodes.
HPPD type 2 doesn’t usually come with a warning aura. Instead, episodes happen suddenly, without a sign that they’re coming. During an episode, you may feel like you’ve lost some or all control. HPPD type 2 can greatly affect your ability to function and take part in daily activities.
Hallucinogen Persisting Perception Disorder Symptoms
Some people report episodes of HPPD (type 1) as pleasant, like a “free trip” where they get the good feelings of a hallucinogen without taking a drug. But more commonly, episodes of both types cause feelings of distress and anxiety.
Flashbacks are one common symptom of HPPD. When you have one, the vision or experience of a past event springs into your mind suddenly. Often, these are negative events that feel intrusive, unwanted, and unpleasant.
Many other vision changes can happen during HPPD. These include:
Visual hallucinations, or seeing things that aren’t real. These can be shapes, animals, people, or simply lights.
Altered motion perception, which changes how you are able to judge things in motion. They may seem to move in slow motion or speed up. Objects may seem to move when they’re actually still.
Flashes of color in your vision.
Intensified colors, or making colors seem enhanced. You may also see colors as different shades than they actually are.
Trails or tracers, or when the image of objects seem to linger even after they move, creating a repeated “trail” of the object as it moves. Or you may continue to see an object even after it’s gone from your vision (an “after image”).
Halos, or rings of light around objects. You may see a glow around streetlights, for example.
Size distortion, where you see objects as bigger or smaller than they actually are.
Metamorphopsia, which distorts your view of objects, especially straight lines. (You see them as wavy.)
Visual snow, or a grainy film over your vision that looks like a TV screen with no signal.
Floaters, which arespots that drift in front of your vision.
Some non-vision symptoms can happen, too. These include:
- Head pressure or tingling throughout your body
- Tinnitus (ringing in your ear)
- Confusion or unclear thoughts
- Depersonalization/derealization (DP/DR), a state in which you feel detached from your body and the world stops feeling real
HPPD is different from other psychotic disorders because while you’re having an episode, you’re aware of it, and you know that what you’re seeing isn’t real.
Hallucinogen Persisting Perception Disorder Causes
Although researchers don’t know why some people get HPPD and others don’t, they know HPPD happens because you’ve used hallucinogenic drugs in the past. According to studies, the amount of a substance you took doesn’t seem to make a difference in your risk of getting HPPD. But some substances are more likely to cause it than others.
The substances most commonly linked to HPPD include:
LSD (lysergic acid diethylamide). Studies show LSD (also called acid) is the most common hallucinogenic drug that can cause HPPD. LSD is a lab-made chemical that is in a class of drugs called psychedelics. In its pure state, it’s a white crystalline substance, but you only need a very small amount to feel the effects. People typically take the drug in sugar cubes or on small gelatin sheets that dissolve on the tongue.
DMT (dimethyltryptamine). This psychedelic is the active ingredient in the drug ayahuasca. People take it by smoking it or drinking it as a brew.
MDMA (3,4-methylenedioxymethamphetamine). This stimulant and psychedelic, also called molly or ecstasy, typically comes in tablet form, but it can also be crushed and snorted or smoked.
Psilocybin. Also called “magic mushrooms,” these psychedelic drugs look just like ordinary mushrooms. You can take them in dried form in a capsule.
Mescaline(peyote). This psychedelic drug comes from the Mexican peyote cactus. You chew it or take it in dried form as a capsule.
Cannabis (marijuana). Studies show marijuana – specifically THC, the chemical in marijuana responsible for its mind-altering effects – is the most commonly reported drug people with HPPD used in the past.
Ketamine. This drug is approved for use as an injectable, short-acting anesthetic and a nasal spray for depression. When abused, it causes hallucinations and disconnection from reality.
In very rare cases, people have had HPPD without ever having taken a hallucinogenic drug.
You may be at a higher risk of getting HPPD if you live with:
- A personal or family history of anxiety
- Tinnitus
- Eye floaters
- Problems with concentration
Hallucinogen Persisting Perception Disorder Diagnosis
Typically, doctors look for three things when diagnosing someone with HPPD:
- You’re having visual symptoms you’ve had before when you were under the influence of drugs.
- These symptoms are making you feel a lot of distress and disrupting your social and work life.
- There isn’t another cause for the symptoms.
HPPD is usually a diagnosis that happens after your doctor rules out other causes, such as:
- PTSD
- Epilepsy
- Schizophrenia
- Anxiety disorder
- Brain lesions
- A brain infection (encephalitis)
- Sleep-related hallucinations, which can happen as you’re waking up or falling asleep, which can be related to a sleep disorder
- Delirium from illness or lack of sleep
Your doctor may give you an electroencephalogram (EEG) test, to look at your brain’s electrical activity.
Hallucinogen Persisting Perception Disorder Treatment
There’s no definitive treatment for HPPD. But once your doctor diagnoses you with HPPD, they may want to try certain medications to help ease your symptoms. The main choices for HPPD treatment include:
- Clonidine. This drug is typically used to lower blood pressure. It works in your brain to alter certain nerve impulses. You take it as a tablet.
- Benzodiazepines. These drugs (Klonopin, Xanax) are sometimes called “benzos.” They slow down activity in your brain and nervous system. These drugs may work well for people with HPPD type 2.
Other second-line drugs your doctor may try include:
- Naltrexone, a drug that helps block the effects of narcotics
- Calcium channel blockers or beta-blockers, drugs typically used to lower blood pressure
Researchers are looking into whether brain stimulation may work as a way to relieve HPPD symptoms, but studies are still ongoing.
Research shows that if you live with depression (with or without anxiety), HPPD symptoms may last longer for you and treatment may not work as well.
Living With Hallucinogen Persisting Perception Disorder
Because HPPD involves feelings of anxiety, you may find certain lifestyle practices helpful in easing stress and soothing mental symptoms. To improve overall mental and physical health:
- Get regular exercise.
- Eat a well-rounded diet with nutritious foods.
- Drink plenty of water.
- Prioritize quality sleep – not too much and not too little.
- Practice relaxation techniques such as deep breathing exercises, mindfulness, and meditation.
- Treat other medical conditions, especially any mental health issues that could make the risk of HPPD worse.
Takeaways
- HPPD is a condition that causes hallucinations and visual disturbances without the recent influence of any substance.
- You get HPPD days, months, or years after taking hallucinogenic drugs.
- You may have mild symptoms, or HPPD may disrupt your quality of life.
- Treatment for HPPD may include medication and anxiety-reducing lifestyle changes.
Hallucinogen Persisting Perception Disorder FAQs
What’s the occurrence rate of HPPD? HPPD is rare. Although data is limited, research shows only 4% to 4.5% of people who take hallucinogenic drugs get it.
Does HPPD cause headaches? Typically, HPPD only affects vision and doesn’t cause head pain.
Is HPPD a dissociative disorder? HPPD can cause dissociation from reality, but it isn’t considered a dissociative disorder. Depersonalization/derealization disorder – a dissociative disorder that makes you feel unattached from your mind, body, and surroundings – is something your doctor will rule out before diagnosing you with HPPD.
What is the prognosis for HPPD? How HPPD affects you long-term can depend on the type you have. HPPD type 1 is usually short-lived and causes very little distress. HPPD type 2 lasts longer and causes more intense symptoms. It can be harder to get symptoms to go away for type 2, and it may mean you need to treat it for the rest of your life.
How do you determine HPPD? Doctors look for three things: Your episodes happen after you took drugs, especially psychedelic ones; your symptoms cause distress and interrupt your daily life; and you don’t have other conditions causing your symptoms, such as schizophrenia, a head injury, or a brain infection. Your doctor may perform tests to rule out other disorders or give you an EEG to monitor your brain activity.
What is the difference between HPPD and flashbacks? Flashbacks are common in people with posttraumatic stress disorder (PTSD). In PTSD, the flashbacks take over many of your senses at once and enhance your feeling of being in the past. HPPD flashbacks tend to be milder and only affect your vision.
