hallucinogenpersisting

Hallucinogen persisting perception disorder, commonly abbreviated as HPPD, is a condition characterized by persistent or recurrent visual disturbances that follow the use of hallucinogenic substances such as LSD, psilocybin, mescaline, or related compounds. The most typical symptoms are visual phenomena including geometric patterns, flashes of color, trailing or afterimages, halos around objects, intensified colors, micropsia or macropsia, and a sensation of visual “snow.” These effects can be intermittent or continuous and may persist for months to years after drug exposure. Some individuals also experience anxiety, depression, or functional impairment linked to the perceptual symptoms.

Causes and pathophysiology are not fully understood. The prevailing view is that hallucinogens can trigger long-lasting changes in visual processing and neural networks, potentially involving serotonergic 5-HT2A receptor–mediated pathways and cortical or thalamocortical circuits. Not all users develop HPPD, and risk may relate to dose, frequency of use, individual susceptibility, and concurrent substance use.

Diagnosis is clinical and based on a history of hallucinogen use and persistent perceptual disturbances, with no other medical explanation. HPPD is a diagnosis of exclusion; differential diagnoses include migraine aura, retinal or optic disorders, seizures, brain lesions, and Charles Bonnet syndrome.

Management emphasizes education, reassurance, and avoidance of further hallucinogen exposure. Many cases improve over time; some persist for extended periods. Treatments are individualized and primarily supportive, addressing comorbid anxiety or mood disorders. Pharmacologic options have shown limited and inconsistent results in case reports, and there are no established, evidence-based medications for HPPD.