Glossary: Psychedelic Medicine

5-HT2A Receptor

A serotonin receptor widely distributed in the cerebral cortex and the principal receptor responsible for the characteristic effects of classic psychedelics, including altered perception, cognition, emotion, and sense of self.

7-Hydroxymitragynine

A naturally occurring alkaloid present in small amounts in kratom and formed through metabolism of mitragynine. It contributes substantially to kratom's analgesic effects.

Hallucination

A sensory perception occurring without an external stimulus that is experienced as real, such as hearing voices or seeing images that are not present.

Hallucinogen

An older umbrella term for substances that alter perception. Increasingly replaced by more precise pharmacologic classifications.

Hallucinogen Persisting Perception Disorder (HPPD)

A rare condition characterized by persistent or recurrent visual disturbances following hallucinogen use despite the absence of acute intoxication.

Herbalist

A practitioner who uses medicinal plants to support health and treat illness. Herbalists may practice within Indigenous, traditional, Western, or integrative systems of medicine.

Holding Environment

A psychologically safe interpersonal space in which individuals feel supported while exploring difficult emotions, memories, or altered states. The concept originated in psychodynamic theory.

Huesero

A traditional bone setter, found throughout Mexico and South America, who specializes in assessing and treating musculoskeletal injuries using manual techniques, massage, splinting, and traditional remedies.

Hyperacusis

An abnormal sensitivity to everyday sounds that causes ordinary environmental noises to be perceived as uncomfortably loud or painful.

Hypertensive Crisis

A severe elevation in blood pressure that may result in acute organ damage and requires immediate medical evaluation and treatment.