Whether mushrooms can cause a change in eye appearance, specifically pupil size, is a common observation related to the use of certain fungi. Pupil dilation, medically termed mydriasis, is a noticeable physiological effect that occurs after consuming specific types of mushrooms. This effect is a direct result of how the active compounds in these fungi interact with the body’s nervous system.
Which Mushrooms Cause Pupil Dilation?
Only psychoactive mushrooms, often called magic mushrooms, are associated with causing pupil dilation. These effects are linked to fungi belonging to the genus Psilocybe, such as Psilocybe semilanceata, which contain psilocybin and psilocin. Psilocybin converts into psilocin, the chemical primarily responsible for the effects.
Common culinary mushrooms, such as white button, portobello, or shiitake varieties, lack these psychoactive compounds and therefore do not cause changes in pupil diameter. The distinction is based entirely on the presence of the hallucinogenic tryptamines psilocybin and psilocin.
The Physiological Mechanism Behind Mydriasis
Pupil dilation is a direct consequence of psilocin acting as an agonist, meaning it activates specific receptors in the brain. Psilocin is structurally similar to the natural neurotransmitter serotonin, allowing it to bind to and activate serotonin receptors. The primary target for this effect is the serotonin 5-HT2A receptor.
Activation of the 5-HT2A receptor triggers effects consistent with activating the body’s Sympathetic Nervous System (SNS). The SNS is one of the two main branches of the Autonomic Nervous System, which controls involuntary body functions, and is responsible for the “fight-or-flight” response. When the sympathetic system is activated, it prepares the body for action.
Within the eye, the Sympathetic Nervous System controls the radial muscles of the iris. Activation of the SNS causes these radial muscles to contract, pulling the iris outward and resulting in an enlargement of the pupil, or mydriasis. This mechanism explains why psilocybin-containing mushrooms cause the pupils to become noticeably larger. The effect is believed to stem from the drug’s interaction with serotonin receptors leading to sympathetic activation.
Other Physical Manifestations of Psilocybin
The activation of the Sympathetic Nervous System that causes pupil dilation also produces several other physical effects. These manifestations are part of the broader physiological response to the active compounds. One common effect is an increase in heart rate, known as tachycardia, and a rise in blood pressure.
Fluctuations in body temperature are frequently reported, with some individuals experiencing elevated temperatures. The body’s overall response can also include gastrointestinal distress, such as nausea, a common initial physical symptom. Other signs may include sweating, muscle weakness, or a feeling of tension, all stemming from the compound’s systemic effects.