Hallucinogen Persisting Perception Disorder (HPPD)
Hallucinogen Persisting Perception Disorder (HPPD) is a cognitive disorder in which individuals continuously re-experience visual and other sensory hallucinations that they first experienced while intoxicated. The persistent nature of the hallucinations and the fact that they occur while the individual is sober are indications of the presence of HPPD.
HPPD is divided into two types, according to the kinds of hallucinations the person experiences. In Type 1, an individual experiences brief, random flashbacks. In Type 2, the experience is more disturbing and persistent, and an individual may experience consistent changes in vision.
It is important to note that HPPD hallucinations are always obvious as hallucinations to the individual experiencing them and don’t override their reality. Despite that, HPPD can still cause significant distress and interfere with one’s work and social life.
The effects of taking larger doses of hallucinogens should wear off over the course of six to 15 hours. HPPD symptoms, however, persist long after the normal active life of the drug and can be either episodic or mostly continuous. These symptoms can last for weeks, months, and sometimes even years. In some cases, the condition becomes chronic, while in other instances, people can suppress the feelings and function normally.
People with Hallucinogen Persisting Perception Disorder re-experience the same hallucinations they had on a past psychedelic “trip.” Oftentimes, these hallucinations are visual but they can affect the other senses as well. For example, someone with HPPD may see colors more intensely or notice halos of different-colored light around objects. Objects might also appear either too big (macropsia) or too small (micropsia). They might even see someone who isn’t there or hear voices. Auditory experiences, like loud music at a concert, may be more intense than normal.
Hallucinogen Persisting Perception Disorder, as defined by the DSM-5, is specifically caused by hallucinogenic drugs, primarily but not exclusively by LSD (lysergic acid diethylamide). The disorder occurs in about 4.2 percent of people who take hallucinogens.
Hallucinogens, or psychedelics, are a group of drugs, synthetic or natural, that in small doses can cause slight mood and thought changes. LSD affects serotonin and dopamine receptors—“the pleasure pathways” in the brain. In larger doses, hallucinogens can cause transient visual, auditory, and other sensory disturbances colloquially known as “trips.”
Since disturbing hallucinations may also be caused by other disorders, such as neurodegenerative disease, brain lesions, seizure disorders, and others, these causes should be ruled out before a person is diagnosed with HPPD.
There is little evidence that an individual's chances of developing HPPD increase with their frequency of drug use; the disorder can also occur in people who have had little experience with hallucinogens.
Some hallucinogens appear in nature, such as psilocybin (magic mushrooms) and mescaline (peyote), and have been used throughout history to generate visions or mystical insights. Chemically synthesized hallucinogens include ketamine, PCP (phencyclidine or angel dust), dizocilpine, LSD (lysergic acid diethylamide), and MDMA (also known as ecstasy or Molly).
The psychedelic trip is likely caused by the way psychotropic compounds bind with 5-HT2A serotonin receptors. However, more research is needed to understand exactly how hallucinogens work.
HPPD can occur in combination with other mental disorders, such as panic disorder, alcohol use disorder, and depression, according to the DSM-5. Some types of therapy used to treat those conditions may be helpful in managing HPPD symptoms as well.
HPPD is also treated with several types of medication, through regimens that should be tailored to each individual. Some types of drugs that have delivered positive results include antipsychotics, some drugs used for treating PTSD, and naltrexone, which is used to treat opioid and alcohol dependency.
It has been suggested that brain stimulation treatments, such as Repetitive Transcranial Magnetic Stimulation (rTMS), may be effective in treating HPPD, but there has been little evidence as of yet to establish their efficacy.
While there is no cure for Hallucinogen Persisting Perception Disorder, those individuals who suffer from it can find some relief from their symptoms by reducing stress and avoiding substance use. HPPD may also go away on its own over time.