Spectrum of disorders

• Hallucinogen Persisting Perception Disorder (HPPD) — persistent visual phenomena after hallucinogen exposure.
• Substance‑induced psychotic disorder — prolonged psychosis triggered by hallucinogens or repeated exposures.
• Substance‑induced mood or anxiety disorders related to hallucinogen use.
• Protracted perceptual disturbances, depersonalisation/derealisation, and cognitive complaints following recurrent use.

Clinical features & timing

• Symptoms may begin days to months after last use and vary from transient flashbacks to continuous distressing perceptual changes.
• Common visual symptoms: trailing, afterimages, halos, visual snow, intensified colours and palinopsia.
• Psychiatric features: anxiety, panic attacks, depressive episodes, intrusive thoughts, and in some, primary psychotic symptoms (delusions, auditory hallucinations).

Assessment approach

1. Substance history: agent(s), dose, frequency, context (recreational, therapeutic, ceremonial), route, last use and any prior adverse events.
2. Symptom timeline: onset relative to use, triggers, duration, and functional impact (work, concentration, driving).
3. Rule out medical causes: migraine aura, epilepsy (occipital), medication side effects, visual/ophthalmic disease and metabolic disturbances.
4. Screen for comorbid psychiatric disorders, suicidality and substance use severity; obtain collateral history where possible.

Investigations

• Basic: visual acuity, fundoscopy, blood tests (glucose, electrolytes, thyroid), and urine toxicology as available.
• Consider EEG if seizures suspected and MRI brain if focal neurological signs or atypical progression.
• Refer to ophthalmology/neuro‑ophthalmology for persistent or unexplained visual symptoms.

Management principles

• Begin with psychoeducation and reassurance — explain typical course, encourage avoidance of re‑exposure and triggers (sleep deprivation, cannabis, stimulants).
• Prioritise non‑pharmacological strategies: CBT for anxiety and perceptual coping, mindfulness, sleep hygiene and gradual exposure to visual stimuli.
• Reserve pharmacologic treatments for severe or refractory cases in consultation with psychiatry — options include clonazepam or lamotrigine in selected patients (limited evidence).
• Address comorbid mood/anxiety disorders with standard therapies (psychotherapy, SSRIs/SNRIs) while monitoring for changes in perceptual symptoms.

When to suspect HPPD vs primary psychiatric disorder

• HPPD typically presents with prominent visual phenomena without prominent disorganized thought or negative symptoms seen in schizophrenia.
• Persistent psychosis with florid delusions or auditory hallucinations warrants evaluation for a primary psychotic disorder; note family history and course after abstinence.

Referral & multidisciplinary care

• Urgent psychiatry referral for severe anxiety, suicidality, or persistent psychosis.
• Neuro‑ophthalmology and neurology for unexplained or progressive visual or neurological symptoms.
• Addiction services and community supports for patients with ongoing problematic use or difficulties engaging with care.

Harm reduction & patient advice

• Encourage abstinence from hallucinogens and other substances that may exacerbate symptoms (cannabis, stimulants, alcohol).
• Advise safer practices if cessation is not immediately possible: use with trusted companions, avoid driving, avoid mixing substances and minimise sleep deprivation.
• Provide resources: crisis contacts, peer support groups and written information about HPPD and coping strategies.

Key takeaways

• Hallucinogen‑induced disorders cover a range of persistent perceptual and psychiatric problems — careful assessment and avoidance of re‑exposure are core first steps.
• Non‑pharmacological interventions (CBT, sleep, coping strategies) are first‑line; reserve medications for refractory cases with specialist input.
• Coordinate multidisciplinary follow‑up for severe, progressive or complex presentations.