How does smoking marijuana cause bloodshot eyes?
June 6, 2006 7:23 PM   Subscribe

How does smoking marijuana cause bloodshot eyes?

The stereotype at least is that marijuana smokers have bloodshot eyes.

I'm wondering what physical process causes the bloodshot eyes. Is it irritation from the smoke or some other reaction?
posted by anonymous to Health & Fitness (1 answer total)

This post was deleted for the following reason: answer is easily googleable.

Conjunctival blood vessel congestion is one of the most constant recognizable signs following marihuana smoking. This congestion is related to the dose of the drug; it lasts longer than the increase in heart rate and is still apparent 90 minutes after the end of smoking, but subsides in the following 24 hours. The mechanism of action is not known; it is not related to an irritation from smoke of the cigarette, but rather to a direct action of Δ-9-THC on the conjunctival vessels. An active congestion of the transverse ciliary vessels has been observed in India, among chronic users of cannabis (ganja). It is accompanied by a yellow discoloration of the conjunctiva due to deposition of a yellow pigment around the vessels, and is reported to still be present years after the drug was withheld (Chopra, 1969).
posted by Gyan at 7:49 PM on June 6, 2006

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