Hallucinogen Persisting Perception Disorder Research Articles

Association of Hallucinogen Persisting Perception Disorder with Trait Neuroticism and Mental Health Symptoms

ABSTRACT Hallucinogen Persisting Perception Disorder (HPPD) is considered rare in hallucinogen users although there are conflicting reports about its incidence and prevalence. HPPD may be more common in those with trait neuroticism. In this study, we invited hallucinogen and other drug users to complete an online questionnaire about their use of hallucinogens, their experience of HPPD symptoms, and their trait neuroticism and mental health symptoms. We received 802 responses with 415 of these containing adequate data for further analysis. 39.7% of responders reported symptoms corresponding to Type I HPPD, and 4.3% reported symptoms corresponding to Type II HPPD. We found no significant difference between neuroticism scores for participants with or without HPPD. Individuals with Type II HPPD were more likely to report mental health symptoms including anxiety, obsessional thoughts, paranoia, hypochondria and panic attacks (p < .05). We also found that individuals with Type II HPPD were more likely to report the use of 25I-NBOMe, dextromethorphan, nitrous oxide and benzodiazepines (p < .05). 47.3% of participants had never tested their drugs, making the attribution of HPPD severity to specific drugs difficult. Further work into the development of HPPD is required, particularly with the rise of hallucinogens as potential treatments for depression and other mental illnesses.

The Tolerability and Safety of Psilocybin in Psychiatric and Substance-Dependence Conditions: A Systematic Review.

The objective of this systematic review is to determine the tolerability and safety of psilocybin in a variety of psychiatric and substance-dependence conditions. A systematic review was conducted using Embase, PubMed, Cochrane Central, and Web of Science through September 2023 using the following terminology: "psilocybin" AND "mental-disease" OR "substance-dependence" AND "disease-therapy," in addition to other synonymous key words. Literature reporting acute effects and safety data following the use of psilocybin as the pharmacologic intervention in a clinical trial in adult patients with a psychiatric or substance-dependence condition were included. Following the application of inclusion and exclusion criteria, 16 studies were ultimately included in this review. The most common treatment-emergent adverse effects reported were transient nausea and headache. Transient anxiety was reported as a frequent psychiatric effect, and 3 participants received a benzodiazepine for refractory anxiety during the psilocybin session. Psilocybin demonstrated modest increases in blood pressure and heart rate, and 1 participant received an antihypertensive for sustained hypertension during the psilocybin session. No cases of psilocybin-induced psychosis or Hallucinogen Persisting Perception Disorder were reported. Treatment resistance remains a concern for psychiatric patients and novel therapies are needed to help alleviate the burden of morbidity and mortality. Psilocybin demonstrates promising acute and long-term safety that may allow for its use in psychiatric or substance-dependence conditions as an alternative to standards of care or in treatment-resistant patients. Psilocybin has demonstrated tolerability and safety in recent literature that has investigated its therapeutic potential in a variety of psychiatric or substance-dependence conditions.

Psychedelic use and psychiatric risks.

Research on psychedelics has recently shown promising results in the treatment of various psychiatric disorders, but relatively little remains known about the psychiatric risks associated with naturalistic use of psychedelics. The objective of the current study was to investigate associations between naturalistic psychedelic use and psychiatric risks. Using a sample representative of the US adult population with regard to sex, age, and ethnicity (N=2822), this study investigated associations between lifetime naturalistic psychedelic use, lifetime unusual visual experiences, and past 2-week psychotic symptoms. Among respondents who reported lifetime psychedelic use (n=613), 1.3% reported having been told by a doctor or other medical professional that they had hallucinogen persisting perception disorder. In covariate-adjusted linear regression models, lifetime psychedelic use was associated with more unusual visual experiences at any point across the lifetime, but no association was observed between lifetime psychedelic use and past 2-week psychotic symptoms. There was an interaction between lifetime psychedelic use and family (but not personal) history of psychotic or bipolar disorders on past 2-week psychotic symptoms such that psychotic symptoms were highest among respondents who reported lifetime psychedelic use and a family history of psychotic or bipolar disorders and lowest among those who reported lifetime psychedelic use and no family history of psychotic or bipolar disorders. Although the results in this study should be interpreted with caution, the findings suggest that lifetime naturalistic use of psychedelics might be associated with more unusual visual experiences across the lifetime, as well as more psychotic symptoms in the past 2 weeks for individuals with a family history of psychotic or bipolar disorders and the reverse for those without such a family history. Future research should distinguish between different psychotic and bipolar disorders and should also utilize other research designs (e.g., longitudinal) and variables (e.g., polygenic risk scores) to better understand potential cause-and-effect relationships.

To treat or not to treat? High-potency benzodiazepine use in a case of comorbid hallucinogen persisting perception disorder and alcohol use disorder.

Hallucinogen persisting perception disorder (HPPD) is characterized by visual disturbances that resemble psychedelic intoxication and linger after use has ceased. The most common substances precipitating HPPD, lysergic acid diethylamide (LSD) and psilocybin, are posited to do so via damage to serotonergic neurons involved in vision. Mr. N is a 37-year-old with a history of alcohol, cannabis, LSD, cocaine, and nicotine use disorders who described visual distortions that resolved when he drank heavily or received benzodiazepines for withdrawal. He did not appear psychotic. Over 20 years after his last LSD use, he continued to experience illusions of halos around objects, moving walls, and figures appearing cartoonish. He understood that his perceptual disturbances were not reality based. During hospitalization for suicidal ideation, laboratory tests, head computed tomography (CT), and electroencephalogram (EEG) studies offered no explanation for his visual disturbances other than HPPD. The visual distortions remitted with scheduled clonazepam treatment, although chemical dependency treatment programs were hesitant to accept him while on a benzodiazepine. This case emphasizes the importance of diagnostic clarification when patients present with perceptual disturbances that do not fit typical psychotic presentations. Our discussion will distinguish misperceptions from hallucinations and review the pathophysiology of HPPD. Last, we will discuss management strategies for patients with co-occurring HPPD and substance use disorders. It is necessary to discern the correct cause of visual disturbances in order to provide proper treatment. The risks and benefits of long-term benzodiazepine use must be weighed when deciding whether to prescribe them for patients with comorbid HPPD and alcohol use disorder. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Temporary and persistent visual phenomena in neurology

Temporary and persistent visual phenomena are afrequent reason for aneurological presentation. The diagnosis can usually be made with the help of astructured anamnesis with determination of the time of onset, the course and symptoms as well as the monocular vs. binocular manifestation. The visual aura in migraine is certainly the most frequent entity to be differentiated. In particular, persistent visual phenomena such as visual snow syndrome, hallucinogen persisting perception disorder and the Charles Bonnet syndrome (CBS) seem to be underdiagnosed in clinical practice for various reasons and are probably not that rare. Instrumental diagnostics are mostly used for exclusion diagnostics and are acomponent of acomplete patient education, but can be indicative for certain questions (CBS, epilepsy). This article presents the most frequent visual phenomena from the neurological practice and their differential diagnoses, guided by acase history.

Hallucinogenic Persisting Perception Disorder: A Case Series and Review of the Literature.

BackgroundHallucinogen persisting perception disorder (HPPD) is characterized by the re-emergence of perceptual symptoms experienced during acute hallucinogen intoxication following drug cessation. The underlying pathophysiology is poorly understood. We report the clinical characteristics and investigation findings of a series of HPPD cases with a literature review of previous case reports. We draw parallels between the features of HPPD and Visual Snow Syndrome (VSS).MethodsRetrospective case series of 13 patients referred from neuro-ophthalmologists. Literature review with 24 HPPD case reports were identified through database search using the terms “hallucinogenic persisting perception disorder” OR “hallucinogen persisting perception disorder.”ResultsLysergic acid diethylamide (LSD), 3,4-Methyl enedioxy methamphetamine (MDMA) and cannabinoid use was common. Cannabinoids and MDMA were mostly used in association with classical hallucinogens. The most frequent symptoms in our patients were visual snow, floaters, palinopsia, photophobia and nyctalopia. In the literature other symptoms included visual hallucinations altered motion perception, palinopsia, tracers and color enhancement. Ophthalmic and neurologic investigations were mostly normal. The majority of patients had ongoing symptoms. Two of our patients fully recovered—one after treatment with benzodiazepine and one without treatment. Twenty-five percent of cases from the literature fully recovered.ConclusionsHPPD presents with heterogeneous visual phenomena on a background of previous classic and non-classic hallucinogen use. Ophthalmic investigations are typically normal. The symptoms of HPPD in our case series overlap with the typical features of Visual Snow Syndrome (VSS). Patients presenting with VSS should be screened for past recreational drug use. The DSM-5 description of HPPD does not include visual snow, nyctalopia, photophobia or floaters. A revision of the diagnostic criteria to include these symptoms may better reflect the typical clinical phenotype. Increased awareness of HPPD as a secondary cause of VSS can avoid extensive investigations. Controlled trials comparing primary and secondary VSS patients are needed to understand the pathophysiology better and optimize treatment for HPPD.

(PO-046) To Treat or not to Treat? High-potency Benzodiazepine Use in a Case of Comorbid Hallucinogen Persisting Perception Disorder and Alcohol Use Disorder

(PO-046) To Treat or not to Treat? High-potency Benzodiazepine Use in a Case of Comorbid Hallucinogen Persisting Perception Disorder and Alcohol Use Disorder

Neuroimaging in Visual Snow - A Review of the Literature

Since the first description of visual snow syndrome (VSS) in 1995, there has been increasing interest particularly within the past 5-10 years in phenotyping the condition and differentiating it from conditions such as migraine with aura and hallucinogen persisting perception disorder. Structural and functional neuroimaging has provided valuable insights in this regard, yielding functional networks and anatomical regions of interest, of which the right lingual gyrus is of particular note. Various modalities, including functional magnetic resonance imaging (fMRI), positron emission tomography (PET), and single photon emission computed tomography (SPECT), have all been studied in patients with visual snow. In this article, we conduct a comprehensive literature review of neuroimaging in VSS.

Flashback phenomena after administration of LSD and psilocybin in controlled studies with healthy participants

BackgroundLSD and psilocybin are increasingly used in phase I trials and evaluated as therapeutic agents for mental disorders. The phenomenon of reoccurring drug-like experiences after the acute substance effects have worn off was described for both substances and especially attributed to LSD. According to the DSM-V, the persisting and distressing manifestation of these experiences is called hallucinogen-persisting perception disorder (HPPD). Data on both conditions is very limited.ObjectiveThis study aims to provide descriptive data on reoccurring drug-like experiences after the administration of LSD and psilocybin in controlled studies with healthy participants.Methods and materialsData from 142 healthy subjects enrolled in six double-blinded, placebo-controlled, randomized cross-over studies were analyzed. In total, 60 subjects received LSD; 27 subjects received LSD, MDMA, and d-amphetamine; 31 subjects received LSD and psilocybin; and 25 subjects received psilocybin and escitalopram. At the end-of-study visit (mean 39.8 days after last study session, SD 37.2), subjects were asked for any reoccurring drug effects since the initial substance effects had worn off. Those reporting reoccurring perception changes more than 24 h after administration were contacted for follow-up (mean follow-up duration: 31.2 months, SD 28.6).ResultsThirteen out of 142 subjects reported reoccurring drug-like experiences (LSD: seven, psilocybin: two, both: four). The reported phenomena were predominantly mild and perceived as neutral to pleasant. Flashbacks were mostly of visual nature, lasted for seconds to minutes, and occurred within a week after the last drug administration. Two subjects reported distressing experiences that subsided spontaneously. One subject reported brief and pleasant visual perception changes which reoccurred for 7 months. None of the subjects reported impairment in their daily lives. None of the cases met DSM-V criteria for HPPD.ConclusionReoccurring drug-like experiences after the administration of LSD and psilocybin are a common phenomenon occurring in up to 9.2% of healthy subjects (7.8% for LSD, 8.3% for psilocybin and 14.3% if both substances are administered). Additionally, our work suggests that flashback phenomena are not a clinically relevant problem in controlled studies with healthy participants.

A retrospective analysis of the “Neverending Trip” after administration of a potent full agonist of 5-HT2A receptor – 25I-NBOMe

Background5-HT2A receptor (e.g. 25I-NBOMe) agonists not only pose risks of acute intoxication but also long-term effects and significant adverse reactions, e.g. hallucinogen persisting perception disorder (HPPD), derealization, and depersonalization. AimsWe evaluated the risk associated with single and repeated use of 25I-NBOMe. We aimed to identify factors that may increase the risk of HPPD, increase its severity and determine the time when the first symptoms appear. Herein, we report the first extensive evaluation of 25I-NBOMe-induced HPPD. MethodWe assessed all reports (58) collected by The Pomeranian Pharmacovigilance Centre (PPC) from 2013 to 2020. ResultsThe study included a total of 58 reports of adverse reactions caused by 25I-NBOMe. In the case of 15 reports (in patients aged 19–26 years), symptoms persisted many months after the discontinuation of 25I-NBOMe. The most common were: pseudohallucinations, bizarre delusions, derealizations and in some cases development or worsening of depression has been diagnosed. HPPD-like symptoms were most common in patients who took the drug regularly (i.e., several times a month). The risk of HPPD-like symptoms is higher in patients who have severe visual pseudohallucinations, severe bizarre delusions, derealization and/or depersonalization onset immediately after taking the drug. Recurrence of HPPD symptoms may be provoked by many factors, however, there is some cases there is no apparent reason. HPPD after 25I-NBOMe use can last from 2 months up to 2 years. In some patients, pharmacological treatment was necessary due to 25I-NBOMe-induced HPPD and depression. ConclusionsThe study showed long-lasting effects after 25I-NBOMe administration and allowed for the determination of HPPD risk factors.

Visual Phenomena Associated With Migraine and Their Differential Diagnosis.

Visual phenomena are of many different kinds; their differential diagnosis is usually possible with directed history-taking. In this review, we describe common visual phenomena that must be distinguished from a migraine aura. This review is based on publications retrieved by a selective search in PubMed and the Web of Knowledge/Science, with special attention to the current classification of the International Headache Society and the recommendations of the German Migraine and Headache Society. The following search terms were used: "visual phenomena/phenomenon," "migraine aura," and "persistent/complication/ long-lasting/ongoing." The most helpful questions for differential diagnosis are whether the symptoms are present in one eye only or in both, whether their onset was sudden or over minutes or days, and whether the phenomenon has occurred only once or repeatedly, or is persistently present. A visual aura associated with migraine must be distinguished, in rare cases, from an isolated epileptic aura, from cerebral/retinal ischemia, or from visual snow. Further differential diagnoses include a persisting perceptual disturbance after hallucinogen use (HPPD, "hallucinogen persisting perception disorder") and the Charles Bonnet syndrome (CBS); the latter arises as a consequence of severely impaired vision. Posterior reversible encephalopathy syndrome (PRES) is rare and generally reveals itself over its further course through the appearance of additional clinical manifestations. Primary ophthalmological causes can usually be readily identified and classified by ophthalmological examination. Patients with visual phenomena typically consult physicians from various medical specialties. A correct differential diagnosis can be made based on the history if the physician views the symptoms in their overall context to determine the particular disease entity that is responsible.

Hallucinogen Persisting Perception Disorder Following Recreational Dextromethorphan Use

Hallucinogen Persisting Perception Disorder Following Recreational Dextromethorphan Use

Migraine prevalence in visual snow with prior illicit drug use (hallucinogen persisting perception disorder) versus without

Background and purposeThis study was undertaken to investigate migraine prevalence in persons with hallucinogen persisting perception disorder (HPPD) presenting as visual snow syndrome (VSS).MethodsPersons with visual snow as a persisting symptom after illicit drug use (HPPD) were recruited via a Dutch consulting clinic for recreational drug use. A structured interview on (visual) perceptual symptomatology, details of drugs use, and medical and headache history was taken. As a control group, persons with visual snow who had never used illicit drugs prior to onset were included. The primary outcome was lifetime prevalence of migraine. Symptom severity was evaluated by the Visual Snow Handicap Inventory (VHI), a 25‐item questionnaire.ResultsNone of the 24 HPPD participants had migraine, whereas 20 of 37 (54.1%) controls had migraine (p < 0.001). VHI scores did not differ significantly between the two groups; in both groups, the median score was 38 of 100. In most HPPD cases (17/24, 70.9%), visual snow had started after intake of ecstasy; other psychedelic drugs reported included cannabis, psilocybin mushrooms, amphetamine, 4‐fluoroamphetamine, 3‐methylmethcathinone, 4‐Bromo‐2,5‐dimethoxypenethylamine, and nitrous oxide.ConclusionsWhereas none of the HPPD participants had migraine, more than half of the visual snow controls without prior use of illicit drugs had migraine. This suggests that at least partly different pathophysiological factors play a role in these disorders. Users of ecstasy and other hallucinogens should be warned of the risk of visual snow. Further studies are needed to enhance understanding of the underlying neurobiology of HPPD and VSS to enable better management of these conditions.

Two hundred and forty-eight cases of visual snow: A review of potential inciting events and contributing comorbidities.

To review characteristics and outcomes of all cases of visual snow seen at our institution, with attention to possible triggering events or comorbidities. This is a retrospective case series of patients seen at our tertiary care center from January 1994 to January 2020. Charts were reviewed if they contained the term "visual snow". Of the 449 charts reviewed, 248 patients described seeing visual snow in part or all of their vision. Thirty-eight reported transient visual snow as their typical migraine aura. Of the remaining 210 patients, 89 were reported to have either an inciting event or contributing comorbidity for their visual snow symptoms, including: Post-concussion (n = 15), dramatic change in migraine or aura (n = 14), post-infection (n = 13), hallucinogen persisting perception disorder (n = 10), ocular abnormalities (n = 7), idiopathic intracranial hypertension (n = 4), neoplastic (n = 1), and posterior cortical atrophy (n = 1). Some patients had partial improvement with benzodiazepines (n = 6), lamotrigine (n = 5), topiramate (n = 3) and acetazolamide (n = 3). Presenting characteristics were similar, but patients with visual snow attributed to an inciting event or contributing comorbidity were more likely to have some improvement in their symptoms by last follow-up compared to spontaneous visual snow (p < .001). Though most cases of visual snow are spontaneous, potential secondary causes should be recognized by clinicians. Patients who develop visual snow after an inciting event or related to an underlying comorbidity may have a better prognosis than those in whom it develops spontaneously. In select cases, treatment of the suspected underlying cause may significantly alleviate the otherwise typical intractable visual disturbances associated with visual snow.

Who takes the trip? Personality and hallucinogen use among college students and adolescents

Research examining hallucinogen use has identified potential benefits, as well as potential harms, associated with use. The acute effects of hallucinogen use can be intense, disorienting, cognitively impairing, and may result in perceptual changes mimicking aspects of temporary psychosis. Hallucinogen use may also lead to the onset of more chronic issues, such as Hallucinogen Persisting Perception Disorder, which impairs daily functioning even when sober. However, research on factors that predict who will misuse hallucinogens is an understudied area. In particular, while sensation seeking, impulsivity, and emotion dysregulation have all been shown to be predictive of problematic substance misuse, there is almost no research on how these personality variables predict hallucinogen use. The present study assessed how these personality traits predicted hallucinogen use in a sample of college undergraduates (N = 10,251) and a sample of adolescents in an inpatient residential psychiatric hospital (N = 200). Results indicated that facets of sensation seeking, impulsivity, and emotion dysregulation positively predicted ever having used hallucinogens, earlier initiation of use, and lifetime use among college students. Findings also indicated that facets of sensation seeking, impulsivity, and emotion dysregulation positively predicted having ever used hallucinogens in the adolescent inpatient sample. Results highlight the need for more research on who is likely to misuse hallucinogens. If confirmed in future research, the findings presented herein indicate viable personality variables as predictors. This is especially important as there has been a recent explosion of research on the positive benefits of therapeutic hallucinogen use.

Psychotic and Still Tripping—Hallucinogen Persisting Perception Disorder and First Break Psychosis in an Adolescent

Psychotic and Still Tripping—Hallucinogen Persisting Perception Disorder and First Break Psychosis in an Adolescent

Visual snow syndrome: A clinical and phenotypical description of 1,100 cases.

ObjectiveTo validate the current criteria of visual snow and to describe its common phenotype using a substantial clinical database.MethodsWe performed a web-based survey of patients with self-assessed visual snow (n = 1,104), with either the complete visual snow syndrome (n = 1,061) or visual snow without the syndrome (n = 43). We also describe a population of patients (n = 70) with possible hallucinogen persisting perception disorder who presented clinically with visual snow syndrome.ResultsThe visual snow population had an average age of 29 years and had no sex prevalence. The disorder usually started in early life, and ≈40% of patients had symptoms for as long as they could remember. The most commonly experienced static was black and white. Floaters, afterimages, and photophobia were the most reported additional visual symptoms. A latent class analysis showed that visual snow does not present with specific clinical endophenotypes. Severity can be classified by the amount of visual symptoms experienced. Migraine and tinnitus had a very high prevalence and were independently associated with a more severe presentation of the syndrome.ConclusionsClinical characteristics of visual snow did not differ from the previous cohort in the literature, supporting validity of the current criteria. Visual snow likely represents a clinical continuum, with different degrees of severity. On the severe end of the spectrum, it is more likely to present with its common comorbid conditions, migraine and tinnitus. Visual snow does not depend on the effect of psychotropic substances on the brain.

Faces of HPPD: Hallucinogen Persisting Perception Disorder Patient Survey Results and a Descriptive Analysis of Patient Demographics, Medical Background, Drug Use History, Symptoms, and Treatments

Objective: The purpose of the present study was to obtain patient information across a wide geography about medical history, drug use, symptoms, and treatments of individuals diagnosed with hallucinogen persisting perception disorder (HPPD). Methods: The study was an internet survey that yielded 26 HPPD patients from North America (81%), Europe (12%), and South America (almost 8%), predominantly male (73%), white (92%), with a median age of 24.5 (range, 18 to 63) years, who have been living with HPPD from a period of <1 year to well over 10 years. Results: History of preexisting mood disorders was reported (100%). Previous hallucinogen drugs used include lysergic acid diethylamide, psilocybin, 3,4-methylenedioxymethamphetamine, and mescaline in highest frequencies. There is a high percentage of current use of benzodiazepines (34.6%) and dependency (78% of those using). Current marijuana use is present for 19%, of which all claim dependency. All patients reported experiencing long-term and ongoing symptoms such as depersonalization (92.3%), visual snow, floaters, trailing afterimages and anxiety (96.2% for each factor). Suicide ideation was pronounced (over 69%). HPPD treatments included benzodiazepines (50%), neuroleptics (23%), anticonvulsants (35%), and receiving counseling (62%). Conclusions: HPPD is an understudied mental disorder that has a complex and unpredictable nature with overlapping psychiatric, psychological, and neurological symptoms. Controlled, evidence-based clinical studies are needed for improvements in diagnosing and treating HPPD. There is concern for patients’ well-being, particularly concerning high reported suicide ideation and dependency on drugs currently used (even if they are prescribed). Improved education for health care professionals and patients is also needed.

Hallucinogen persisting perception disorder: A literature review and three case reports

The paper describes diagnostic criteria, clinical presentation and types of hallucinogen persisting perception disorder (HPPD), as well as current approaches to the treatment of this phenomenon using available scientific sources. Three case reports are also presented to demonstrate different types of this disorder. The first case report describes a 23-year old patient with a previous history of cannabis consumption who reported HPDD type I after the use of psilocybin mushrooms with small amounts of alcohol and hash. A month later, after cannabis use, the same visual and auditory distortions appeared again. During the following year, hallucinations recurred with the consumption of natural cannabinoids but not with alcohol intake. The symptoms have reduced within a year. Surprisingly, both other cases belonging to HPDD type II appeared in patients who consumed ecstasy, although MDMA is generally not considered a hallucinogen and hallucinations are not frequently reported after MDMA consumption. In both cases of HPPD type II after the use of ecstasy, the condition was very stressful and frightening. Both patients sought medical help and received tofisopam, lamotrigine and sertraline. After that, in both cases visual impairments have smoothed, but have not passed completely. Scientific sources suggest that HPPD may affect more than 50% of hallucinogen users and this disorder is often underdiagnosed. Therefore, patients suffering from HPPD can present in various clinical settings, and clinicians should be aware of this condition.

Hallucinogen Persisting Perception Disorder: Etiology, Clinical Features, and Therapeutic Perspectives.

Hallucinogen Persisting Perception Disorder (HPPD) is a rare, and therefore, poorly understood condition linked to hallucinogenic drugs consumption. The prevalence of this disorder is low; the condition is more often diagnosed in individuals with a history of previous psychological issues or substance misuse, but it can arise in anyone, even after a single exposure to triggering drugs. The aims of the present study are to review all the original studies about HPPD in order to evaluate the following: (1) the possible suggested etiologies; (2) the possible hallucinogens involved in HPPD induction; (3) the clinical features of both HPPD I and II; (4) the possible psychiatric comorbidities; and (5) the available and potential therapeutic strategies. We searched PubMed to identify original studies about psychedelics and Hallucinogen Persisting Perception Disorder (HPPD). Our research yielded a total of 45 papers, which have been analyzed and tabled to provide readers with the most updated and comprehensive literature review about the clinical features and treatment options for HPPD.