Disorders Due to Use of Hallucinogens (ICD-11: 6C49)

1. Introduction

Disorders due to hallucinogen use represent a set of clinical conditions resulting from the consumption of psychoactive substances that profoundly alter perception, thought, and emotions. These substances include natural compounds such as psilocybin (found in mushrooms), mescaline (derived from peyote cactus), and synthetic compounds such as lysergic acid diethylamide (LSD), as well as other substances such as DMT (dimethyltryptamine) and MDMA under certain circumstances.

The clinical importance of these disorders lies mainly in the acute consequences of intoxication, which may include psychotic episodes, risky behaviors, and intense panic reactions. Unlike other substances of abuse, dependence on hallucinogens is extremely rare and there is no clinically recognized withdrawal syndrome associated with its discontinuation. This unique characteristic differentiates hallucinogen-related disorders from other substance use disorders.

Although recreational use of hallucinogens has increased in some populations, especially among young adults, serious disorders related to their use remain relatively uncommon compared with other substances. However, when they occur, they can result in dramatic clinical presentations that require urgent medical intervention. Correct coding of these disorders is fundamental for epidemiological tracking, mental health service planning, clinical research, and ensuring appropriate treatment. Diagnostic accuracy is also essential to differentiate these disorders from primary psychiatric conditions that may present with similar symptoms.

2. Correct ICD-11 Code

Code: 6C49

Description: Disorders due to use of hallucinogens

Parent category: Disorders due to substance use

Official definition: Disorders due to use of hallucinogens are characterized by the pattern and consequences of hallucinogen use. Thousands of compounds possess hallucinogenic properties, many of which are found in plants (such as mescaline) and fungi (such as psilocybin) or are chemically synthesized (such as LSD). These compounds have primarily hallucinogenic properties, although some may also exhibit stimulant effects.

Much of the morbidity associated with these compounds results from acute effects related to hallucinogen intoxication. Hallucinogen dependence is rare and hallucinogen withdrawal has not been described as a clinically significant syndrome. Among mental disorders related to hallucinogen use, hallucinogen-induced psychotic disorder is the most frequently observed, although worldwide it remains relatively uncommon when compared to psychotic disorders induced by other substances.

Code 6C49 serves as the main category that encompasses various specific subtypes of hallucinogen-related disorders, allowing detailed classification of different clinical presentations.

3. When to Use This Code

The code 6C49 should be used in specific clinical situations where there is clear evidence of hallucinogen use and direct consequences of this use:

Scenario 1: Acute Hallucinogen Intoxication A 22-year-old patient is brought to the emergency department presenting with intense visual hallucinations, alterations in time perception, mydriasis (dilated pupils), tachycardia, and extreme anxiety after consuming mushrooms containing psilocybin. The patient reports that the walls are "breathing" and experiences synesthesia (mixing of senses). This is a typical case of acute intoxication that requires code 6C49 with the appropriate specifier for intoxication.

Scenario 2: Psychotic Episode Induced by LSD A 25-year-old female patient develops persistent psychotic symptoms, including paranoid delusions and auditory hallucinations, after LSD use at a music festival. The symptoms persist for more than 48 hours after substance use and require psychiatric hospitalization. This case represents a hallucinogen-induced psychotic disorder, which is the most common complication among disorders related to these substances.

Scenario 3: Persistent Perceptual Disorder (Flashbacks) A 30-year-old patient with a history of frequent LSD use in the past presents with recurrent episodes of visual distortions and perceptual alterations similar to those experienced during intoxication, even without recent substance use. These "flashbacks" cause significant distress and interfere with occupational functioning. Code 6C49 is appropriate with the specifier for persistent perceptual disorder.

Scenario 4: Harmful Use of Hallucinogens A 28-year-old patient regularly uses DMT and has developed significant negative consequences, including neglect of professional responsibilities, family conflicts related to use, and repeated episodes of risky behavior during intoxication. Although not presenting with dependence (which is rare with hallucinogens), the pattern of harmful use justifies code 6C49 with appropriate specifier.

Scenario 5: Anxiety Disorder Induced by Hallucinogens A 26-year-old female patient develops recurrent panic attacks and generalized anxiety that began after a traumatic experience with mescaline ("bad trip"). The anxiety symptoms persist for weeks after use and require specific treatment. Code 6C49 is applicable when anxiety is clearly attributable to hallucinogen use.

Scenario 6: Intoxication with Medical Complications A 20-year-old patient is admitted with NBOMe intoxication (synthetic hallucinogen) presenting with hyperthermia, seizures, and rhabdomyolysis. The severity of medical complications associated with hallucinogen intoxication justifies the use of code 6C49 along with codes for the specific complications.

4. When NOT to Use This Code

It is essential to recognize situations where code 6C49 is not appropriate, avoiding coding errors:

Primary Psychotic Disorders: If a patient has schizophrenia or another primary psychotic disorder and uses hallucinogens occasionally, but the psychotic symptoms precede the use or persist independently of it, the primary code should be that of the psychotic disorder, not 6C49. Careful clinical history is essential for this differentiation.

Cannabis Use with Hallucinogenic Properties: Although cannabis may produce some altered perceptual experiences, disorders related to cannabis use should be coded as 6C41, not 6C49. This distinction is important even when users report "hallucinogenic" effects of cannabis.

MDMA (Ecstasy) Intoxication with Predominance of Stimulant Effects: MDMA has mixed properties (stimulant and entactogenic/hallucinogenic). When stimulant effects predominate and the clinical presentation is more consistent with stimulant intoxication, other codes may be more appropriate. Classification depends on the specific clinical profile.

Anticholinergic-Induced Disorders: Substances such as scopolamine or plants containing tropane alkaloids can cause delirium and hallucinations, but are classified differently from classic hallucinogens. These intoxications have distinct clinical presentations (usually delirium with agitation, rather than the organized perceptual experiences of classic hallucinogens).

Single Experimental Use without Consequences: A patient who tried psilocybin once, years ago, without developing any disorder or negative consequence, should not receive code 6C49. The code is reserved for situations where there is a clinically significant disorder.

Perceptual Symptoms Related to Other Medical Conditions: Visual hallucinations caused by migraine, temporal lobe epilepsy, or other neurological conditions should not be coded as 6C49, even if the patient has a history of hallucinogen use in the past.

5. Step-by-Step Coding Process

Step 1: Assess Diagnostic Criteria

Confirmation of diagnosis requires a comprehensive evaluation that includes:

History of Use: Obtain detailed information about which hallucinogenic substance was used (LSD, psilocybin, mescaline, DMT, NBOMe, etc.), quantity, frequency, route of administration, and time since last use. Chronology is crucial to establish the causal relationship between use and symptoms.

Symptom Assessment: Carefully document clinical manifestations, including perceptual alterations (visual, auditory, or tactile hallucinations), changes in thinking, mood alterations, autonomic symptoms (tachycardia, mydriasis, hypertension), and any psychiatric or medical complications.

Physical Examination: Perform complete physical examination, paying special attention to vital signs, neurological examination, and characteristic signs of hallucinogen intoxication (mydriasis, hyperreflexia, incoordination).

Toxicological Tests: When available, urine or blood tests can confirm the presence of hallucinogens, although many classic hallucinogens (such as LSD) are difficult to detect in standard tests due to low active doses and rapid metabolism.

Comorbidity Assessment: Investigate preexisting psychiatric disorders, use of other substances, and medical conditions that may influence clinical presentation or prognosis.

Step 2: Verify Specifiers

Code 6C49 has subcategories that specify the type of disorder:

Acute Intoxication: Characterized by perceptual, cognitive, and behavioral alterations during or shortly after use. Severity ranges from mild (minimal perceptual experiences without significant distress) to severe (intense panic reactions, risky behavior, need for medical supervision).

Harmful Use: Pattern of use that causes damage to physical or mental health but does not meet criteria for dependence. Document the specific consequences of use.

Hallucinogen-Induced Psychotic Disorder: Psychotic symptoms that emerge during or shortly after use and persist beyond acute intoxication. Specify whether there is predominance of delusions, hallucinations, or mixed symptoms.

Persistent Perceptual Disorder: Recurrence of perceptual alterations similar to those experienced during intoxication, occurring weeks or months after last use. Document the frequency, duration, and functional impact of episodes.

Step 3: Differentiate from Other Codes

6C40 (Disorders due to alcohol use): Alcohol primarily produces sedation, disinhibition, and motor impairment, not the vivid perceptual alterations characteristic of hallucinogens. Alcohol intoxication rarely produces organized visual hallucinations, except in cases of delirium tremens during severe withdrawal.

6C41 (Disorders due to cannabis use): Although cannabis may cause some perceptual alterations, these are generally subtle compared to classic hallucinogens. Cannabis typically causes relaxation, temporal alterations, and increased appetite, while hallucinogens produce profound perceptual distortions and more intense pseudohallucinogenic experiences.

6C42 (Disorders due to synthetic cannabinoid use): Synthetic cannabinoids act on the same receptors as natural cannabis but with much greater potency. Although they may cause psychotic symptoms, the clinical profile differs from classic hallucinogens, often including extreme agitation, severe cardiovascular symptoms, and seizures.

Differentiation is based on the substance used (confirmed by history and, when possible, toxicological tests) and the characteristic symptom profile.

Step 4: Required Documentation

Checklist of Mandatory Information:

• Specific identification of the hallucinogenic substance used
• Date and time of last use
• Quantity and route of administration
• Symptoms present and their temporal evolution
• Vital signs and physical examination findings
• Results of toxicological tests (when available)
• Presence or absence of psychiatric comorbidities
• Concomitant use of other substances
• Functional impact of symptoms
• Treatments administered and response

Appropriate Documentation: Documentation must clearly establish the temporal and causal relationship between hallucinogen use and the symptoms presented, justifying the choice of specific code and its specifiers.

6. Complete Practical Example

Clinical Case

Initial Presentation: A 24-year-old male patient, university student, is brought to the emergency department by friends at 11 PM on a Saturday. According to the companions, the patient ingested approximately 3 grams of dried mushrooms containing psilocybin about 2 hours prior, during a party. Initially he was euphoric and reporting "seeing incredible colors," but progressively became extremely anxious, agitated, and began screaming that "demons were trying to get him."

Evaluation Performed: On examination, the patient appears visibly anxious, with accelerated and sometimes incoherent speech. He reports intense visual hallucinations, describing complex geometric patterns and distortions in the faces of people around him. He refers to intense depersonalization ("I don't recognize myself") and extreme fear of "going crazy forever."

Vital signs: blood pressure 145/92 mmHg, heart rate 118 bpm, respiratory rate 22 breaths/min, temperature 37.2°C. Bilaterally dilated pupils (7mm), reactive to light. Mild tremor in the extremities. Generalized hyperreflexia. Oriented to person and place, but with distorted time perception. No signs of physical trauma.

Additional history obtained after initial stabilization reveals this is the third time using psilocybin mushrooms in the last 6 months. Denies regular use of other substances, except occasional social alcohol. No previous psychiatric history or family history of psychotic disorders.

Diagnostic Reasoning: The clinical presentation is consistent with acute psilocybin intoxication. The chronology (symptoms beginning 1-2 hours after ingestion, expected peak between 2-4 hours) is typical. The symptoms—vivid visual hallucinations, intense anxiety, perceptual alterations, autonomic signs (tachycardia, mydriasis, mild hypertension)—are characteristic of intoxication with serotonergic hallucinogens.

The absence of previous psychiatric history, the clear temporal relationship between use and symptoms, and the specific symptom profile distinguish this case from a primary psychotic disorder. The severity of the reaction (intense panic, need for medical supervision) justifies classification as moderate to severe intoxication.

Coding Justification: The patient was treated in a calm environment, with low sensory stimulation (dark, quiet room), continuous monitoring, and benzodiazepines for anxiety control (lorazepam 2mg). He responded well to treatment, with gradual symptom resolution over 6 hours. He was discharged with guidance on the risks of hallucinogen use and referral for outpatient mental health follow-up.

Step-by-Step Coding

Criteria Analysis:

1. Confirmed use of hallucinogenic substance (psilocybin) - ✓
2. Typical symptoms of hallucinogen intoxication - ✓
3. Clear temporal relationship between use and symptoms - ✓
4. Severity sufficient to require medical attention - ✓
5. Exclusion of other causes (primary psychotic disorder, other substances, medical conditions) - ✓

Code Selected: 6C49 (with specifier for acute intoxication)

Complete Justification: Code 6C49 is appropriate because the patient presents with an acute disorder directly related to hallucinogen use (psilocybin). The clinical presentation is typical of acute intoxication, with characteristic perceptual, cognitive, emotional, and autonomic symptoms. The severity of the reaction (extreme anxiety, need for medical intervention) justifies coding as a clinically significant disorder, not merely as recreational use without consequences.

Complementary Codes:

• Code for acute anxiety symptoms (if coding system allows multiple codes)
• Code for tachycardia, if clinically significant and requiring specific treatment
• Z code (factors related to health status) to document circumstances of use, if relevant to care planning

7. Related Codes and Differentiation

Within the Same Category

6C40: Disorders due to use of alcohol

When to use: Use 6C40 when the primary substance involved is alcohol, manifesting through alcohol intoxication, withdrawal syndrome, dependence, or medical complications related to alcohol (liver disease, pancreatitis, Wernicke's encephalopathy).

Main difference: Alcohol is a central nervous system depressant that causes sedation, disinhibition, motor and cognitive impairment, and can lead to severe physical dependence with potentially fatal withdrawal syndrome. Hallucinogens, on the other hand, are primarily serotonergic agonists that cause profound perceptual alterations without causing significant physical dependence or withdrawal syndrome.

6C41: Disorders due to use of cannabis

When to use: Apply 6C41 when the patient presents with disorders related to the use of natural cannabis (marijuana, hashish), including intoxication, harmful use, dependence, or induced mental disorders (psychosis, anxiety).

Main difference: Cannabis acts primarily on cannabinoid receptors (CB1 and CB2), producing relaxation, subtle temporal alterations, increased appetite, and at high doses, some perceptual alterations. Classic hallucinogens act on serotonergic 5-HT2A receptors, producing much more intense and organized perceptual alterations, including complex visual hallucinations, synesthesia, and mystical or transcendental experiences that rarely occur with cannabis.

6C42: Disorders due to use of synthetic cannabinoids

When to use: Use 6C42 for disorders related to the use of synthetic cannabinoids (known as "spice," "K2," or other commercial names), which are chemical substances that mimic the effects of cannabis but with much greater potency.

Main difference: Although synthetic cannabinoids act on the same receptors as natural cannabis, they are much more potent and unpredictable, frequently causing severe adverse effects including extreme agitation, psychosis, seizures, and cardiovascular toxicity. Classic hallucinogens have a completely different pharmacological profile (serotonergic action) and generally more favorable physical safety profile, although with greater potential for acute adverse psychological reactions.

Differential Diagnoses

Primary Psychotic Disorder (Schizophrenia, Schizoaffective Disorder): Distinguished by chronology - primary psychotic disorders have onset independent of substance use and persist even during prolonged periods of abstinence. Family history of psychosis, prominent negative symptoms, and progressive functional deterioration suggest primary disorder.

Bipolar Disorder with Psychotic Features: Distinguished by the presence of distinct mood episodes (mania, hypomania, depression) that occur independently of substance use, with characteristic episodic history and frequently family history of mood disorders.

Delirium Due to Medical Cause: Delirium presents with fluctuation of level of consciousness, prominent disorientation, and generally has an identifiable medical cause (infection, metabolic disturbance, medications). Intoxication from hallucinogens typically preserves orientation and does not present with the same fluctuation of level of consciousness.

Depersonalization/Derealization Disorder: This primary disorder causes persistent experiences of depersonalization or derealization unrelated to substance use, typically beginning in adolescence or early adulthood and following a chronic course.

8. Differences with ICD-10

Equivalent ICD-10 Code: F16 - Mental and behavioral disorders due to use of hallucinogens

Main Changes in ICD-11:

ICD-11 introduces significant modifications in the classification of disorders related to hallucinogen use. While ICD-10 used the code F16 with subdivisions based on additional digits (F16.0 for acute intoxication, F16.1 for harmful use, etc.), ICD-11 adopts the alphanumeric code 6C49 with a clearer hierarchical structure.

ICD-11 eliminates the category of "dependence syndrome" specific to hallucinogens, explicitly recognizing that hallucinogen dependence is extremely rare and clinically of little significance. ICD-10 included F16.2 (dependence syndrome), which was rarely used in clinical practice due to low prevalence.

Another important change is the greater emphasis in ICD-11 on hallucinogen-induced persistent perceptual disorder (flashbacks), which receives more explicit recognition as a distinct clinical entity. ICD-10 included this condition less specifically under "late-onset psychotic disorder".

Terminology has also been updated to better reflect current scientific knowledge. ICD-11 uses more neutral and clinically precise language, avoiding potentially stigmatizing terms.

Practical Impact:

For clinicians, the most relevant change is the simplification of the coding system and explicit recognition of the unique characteristics of hallucinogens (low dependence potential, absence of withdrawal syndrome). This allows for more precise documentation and facilitates epidemiological research on these disorders.

For health systems, the transition requires updating electronic record systems and training professionals to ensure consistent coding. The greater conceptual clarity of ICD-11 should improve the quality of data collected on hallucinogen-related disorders.

9. Frequently Asked Questions

1. How is the diagnosis of disorders due to hallucinogen use made?

The diagnosis is primarily clinical, based on detailed substance use history and characteristic symptomatic presentation. The clinician should obtain information about which substance was used, quantity, route of administration, and symptom chronology. Physical examination reveals typical signs such as mydriasis, tachycardia, and hyperreflexia. Toxicological tests may be helpful, but many hallucinogens (especially LSD) are difficult to detect in standard tests due to extremely low active doses. The evaluation should include investigation of psychiatric comorbidities and exclusion of other medical causes for the presented symptoms.

2. Is treatment available in public health systems?

Yes, treatment for acute intoxication and complications related to hallucinogen use is generally available in emergency services and psychiatric units of public health systems. Acute management involves primarily supportive measures, a quiet environment with low sensory stimulation, and when necessary, anxiolytic medications. For persistent disorders such as induced psychosis or persistent perceptual disorder, treatment may include outpatient psychiatric follow-up, psychotherapy, and in some cases, antipsychotic medications or mood stabilizers. The availability of specialized services varies by region and local resources.

3. How long does treatment last?

Treatment duration varies significantly depending on the type of disorder. Acute intoxication from classical hallucinogens (LSD, psilocybin) typically resolves within 6-12 hours, although some residual symptoms may persist for 24 hours. "Bad trip" episodes (panic reactions) generally respond well to brief interventions (a few hours) in an appropriate environment. Induced psychotic disorders may require treatment for weeks to months, with most cases resolving completely. Persistent perceptual disorder may be more prolonged, sometimes requiring months of treatment, although it tends to improve gradually over time and with hallucinogen abstinence.

4. Can this code be used in medical certificates?

Yes, code 6C49 can be used in medical certificates when clinically appropriate and necessary to justify absence from work or studies. However, physicians should consider confidentiality issues and potential stigma. In some situations, it may be more appropriate to use more general or descriptive codes (such as codes for acute anxiety or brief psychotic disorder) depending on context and patient needs. The decision should balance diagnostic accuracy with protection of patient privacy and well-being.

5. Can hallucinogens cause permanent brain damage?

There is no robust scientific evidence that classical hallucinogens (LSD, psilocybin, mescaline) cause structural brain damage or direct neurotoxicity. However, they can precipitate persistent psychiatric disorders in vulnerable individuals, particularly those with genetic predisposition to psychosis. Persistent perceptual disorder (flashbacks), although generally non-progressive, can be debilitating in some cases. The greatest risks associated with hallucinogens are psychological (panic reactions, psychotic episodes) and behavioral (accidents due to impaired judgment during intoxication) rather than direct neurotoxicity.

6. Is there a difference between natural and synthetic hallucinogens in terms of risks?

Although natural hallucinogens (psilocybin, mescaline) and synthetic ones (LSD) act through similar pharmacological mechanisms, there are some important differences. Newer synthetic hallucinogens (such as NBOMe) can be significantly more dangerous, with reports of severe toxicity including seizures, hyperthermia, and deaths. Natural substances have a more predictable effects profile, although incorrect identification of plants or fungi can lead to severe intoxications. Potency also varies—LSD is active in micrograms, making precise dosing difficult in recreational contexts. Regardless of origin, all hallucinogens can cause severe adverse psychological reactions.

7. What are the risk factors for developing complications after hallucinogen use?

Several factors increase the risk of complications: personal or family history of psychotic or bipolar disorders (greater risk of precipitating psychosis), use in uncontrolled or threatening environments (increases risk of "bad trips"), high doses or substances of unknown potency, combined use with other substances (especially stimulants), history of unresolved psychological trauma, and use during periods of significant psychological stress. Adolescents and young adults may be particularly vulnerable due to ongoing brain development. The presence of preexisting anxiety disorders can also increase the risk of panic reactions during intoxication.

8. How to differentiate between flashback and recurrence of psychotic disorder?

Flashbacks (persistent perceptual disorder) are typically brief (seconds to minutes), consist mainly of visual distortions (halos, visual trails, color intensification) without delusions or auditory hallucinations, and the patient generally maintains insight that the experiences are not real. They occur spontaneously or are triggered by dark environments, fatigue, or cannabis use. In contrast, recurrences of psychotic disorders involve more complex symptoms (delusions, auditory hallucinations, thought disorganization), longer duration (days to weeks), loss of insight, and often functional deterioration. Careful clinical history, including symptom chronology and response to previous treatments, is essential for differentiation.

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Conclusion

Disorders due to hallucinogen use (ICD-11: 6C49) represent a specific set of clinical conditions with unique characteristics that distinguish them from other substance use disorders. Precise coding requires detailed understanding of hallucinogen pharmacological properties, recognition of characteristic symptom patterns, and careful differentiation from primary psychiatric conditions. Although relatively uncommon globally, when they occur, these disorders may require urgent medical intervention and cause significant suffering. The transition from ICD-10 to ICD-11 brought greater conceptual clarity and recognition of the unique characteristics of these disorders, facilitating more precise diagnosis, treatment, and research.

External References

This article was prepared based on reliable scientific sources:

1. 🌍 WHO ICD-11 - Disorders due to use of hallucinogens
2. 🔬 PubMed Research on Disorders due to use of hallucinogens
3. 🌍 WHO Health Topics
4. 📋 NICE Mental Health Guidelines
5. 📊 Clinical Evidence: Disorders due to use of hallucinogens
6. 📋 Ministry of Health - Brazil
7. 📊 Cochrane Systematic Reviews

References verified on 2026-02-03