What are the changes in the diagnosis of hallucinogen‑related disorders across the Diagnostic and Statistical Manual of Mental Disorders (DSM) versions III, III‑TR (Text Revision), IV, V, and V‑TR (Text Revision), and the International Classification of Diseases (ICD) versions X and XI?

Evolution of Hallucinogen-Related Disorder Diagnosis Across DSM and ICD Versions

DSM Evolution (DSM-III through DSM-5-TR)

The most significant change across DSM versions was the introduction of standardized criteria for substance-induced mental disorders in DSM-IV and the subsequent refinement in DSM-5 to require that substance-induced disorders "resemble" the full criteria for the relevant disorder while removing the requirement that symptoms exceed expected intoxication or withdrawal. 1

DSM-IV Key Changes

• DSM-IV introduced standardized guidelines to differentiate "primary" from "substance-induced" mental disorders, requiring that primary disorders either began prior to substance use or persisted for more than 4 weeks after cessation of acute withdrawal or severe intoxication. 1
• Substance-induced mental disorders were defined as occurring during periods of substance intoxication or withdrawal or remitting within 4 weeks thereafter. 1
• The term "primary" was used (later changed to "independent" in DSM-5) to describe disorders not attributable to substance effects. 1

DSM-5 and DSM-5-TR Modifications

• DSM-5 changed the terminology from "primary" to "independent" to avoid confusion about time sequence or diagnostic hierarchy. 1
• The title was adjusted from "substance-induced" to "substance/medication-induced" disorders to reflect that medications were included in both DSM-IV and DSM-5 criteria but not noted in the DSM-IV title. 1
• A new criterion was added requiring that the disorder "resembles" the full criteria for the relevant disorder, though this represented a reversal of DSM-IV's standardization by removing specific symptom and duration requirements. 1
• The requirement that symptoms exceed expected intoxication or withdrawal symptoms was removed, creating a more flexible but less standardized approach. 1
• DSM-5 specified that the substance must be pharmacologically capable of producing the psychiatric symptoms. 1

Hallucinogen Persisting Perception Disorder (HPPD) Specifics

• HPPD was formally recognized in DSM-IV as a distinct diagnosis characterized by the recurrence of perceptual disturbances without acute or chronic hallucinogen consumption. 2
• The disorder is defined as repeated experience of hallucinations and other perceptual disturbances as a result of prior intoxications, with symptoms potentially lasting 5 years or more. 2, 3
• DSM-5 describes HPPD as a visual perceptual disorder that can persist for months or years, causing severe individual distress. 4
• Current DSM-5 criteria focus primarily on visual phenomena but do not include visual snow, nyctalopia, photophobia, or floaters, which are commonly reported in clinical practice. 5

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ICD Evolution (ICD-10 to ICD-11)

ICD-11 underwent the most substantial restructuring in psychiatric classification history, expanding from 11 to 21 disorder groupings and harmonizing with DSM-5 structure while maintaining a primarily categorical approach. 1

ICD-10 Classification

• ICD-10 used the term "Flashback" (F16.70) to describe brief visual perceptual, mood, and altered states of consciousness effects reminiscent of acute hallucinogen intoxication. 4
• The classification system contained only 11 disorder groupings in the Mental and Behavioural Disorders chapter. 1
• ICD-10 maintained a separate disorder grouping for mental and behavioral disorders with onset during childhood and adolescence. 1

ICD-11 Major Restructuring

• ICD-11 expanded to 21 disorder groupings (adopted May 2019, implemented January 1,2022) based on shared etiology, pathophysiology, and phenomenology. 1
• The WHO eliminated the separate childhood/adolescence disorder grouping, integrating these conditions into other groupings to emphasize developmental continuity across the lifespan. 1
• Harmonization between ICD-11 and DSM-5 was a central aim, influencing the chapter structure of ICD-11. 1

ICD-11 Dimensional Enhancements

• ICD-11 introduced dimensional severity ratings across multiple symptom domains on a 4-point scale (0=not present, 1=mild, 2=moderate, 3=severe) for anxiety, depression, and cognitive domains. 6
• The system permits longitudinal coding of episodicity and current status (first episode, multiple episodes, continuous course; symptomatic, partial remission, full remission). 6
• Despite these additions, changes from ICD-10 to ICD-11 remained relatively modest, with both systems maintaining a categorical approach based on self-reported or clinically observable symptoms. 1

ICD-11 Clinical Utility

• In field studies with 928 clinicians, 82.5%–83.9% rated ICD-11 as "quite" or "extremely" easy to use, significantly higher than ICD-10 ratings. 6
• ICD-11 demonstrated higher diagnostic accuracy, faster time to diagnosis, and superior perceived clinical utility compared to ICD-10. 6
• Inter-rater reliability was high for psychotic disorders but only moderate for mood and anxiety-related disorders, indicating variable performance across diagnostic groups. 6

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Critical Diagnostic Considerations for Hallucinogen-Related Disorders

Prevalence and Clinical Significance

• The prevalence of HPPD is unknown but appears uncommon given the relatively few case reports published despite millions of hallucinogen users since the 1960s and 1970s. 4, 3
• HPPD represents a serious yet uncommon event associated with prior hallucinogen exposure, with renewed importance given psychedelic research for mental disorders. 3

Common Substances Implicated

• Lysergic acid diethylamide (LSD) and LSD-like substances are the most common hallucinogens causing HPPD symptoms. 5, 7
• MDMA (3,4-Methylenedioxymethamphetamine) and cannabinoids are frequently used in association with classical hallucinogens. 5

Clinical Presentation

• Most frequent symptoms include visual snow, floaters, palinopsia, photophobia, and nyctalopia, though DSM-5 criteria do not include all of these. 5
• Other reported symptoms include visual hallucinations, altered motion perception, tracers, and color enhancement. 5
• Many users regard flashback phenomena as benign and even pleasant, distinguishing them from the distressing nature of HPPD. 4

Diagnostic Pitfalls

• Ophthalmic and neurologic investigations are typically normal in HPPD, which can lead to extensive unnecessary testing. 5
• HPPD symptoms overlap significantly with Visual Snow Syndrome (VSS), and patients presenting with VSS should be screened for past recreational drug use. 5
• The disorder must be distinguished from acute hallucinogen-induced psychosis, other substance-induced disorders, and primary psychiatric conditions. 7
• A revision of DSM diagnostic criteria to include visual snow, nyctalopia, photophobia, and floaters may better reflect the typical clinical phenotype. 5

Treatment and Prognosis

• The exact pathophysiological mechanisms underlying HPPD remain elusive despite multiple etiological and therapeutic approaches. 4, 3
• The majority of patients have ongoing symptoms, though approximately 25% of cases in the literature fully recovered. 5
• Lamotrigine has shown promise as the gold standard in treating perceptual disturbance in time and space, while alpha-2 adrenergic drugs (clonidine) and benzodiazepines are considered first-line. 7
• Symptoms can persist for months to years, representing real psychosocial distress requiring long-term management. 2, 3