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Why Do Your Pupils Get Larger When You’re On Drugs? — ‘The Why’

Welcome to the newest edition of The Why.  “Why do your pupils get larger when you’re on drugs?” you ask? Good question. (Besides, it beats answering the question: “Why do I get ingrown hairs on my @ss?”)


Even smoking marijuana can dilate your pupils/Image: Tumblr

Let’s be honest.  This reporter’s eyes have not gotten larger for quite some time. Whereas he might not be adverse to the occasional toke of a natural substance with an attractive lady performer after a show or as a prelude to doing the Hokey Pokey with a gal with socially-casual morals, too many employers have random drug testing these days and since the economy your rockin’ writer no longer has enough paid writing work to do without a part-time day job.

Anyway, if you remember your high school science classes, your pupils dilate as a way of responding to changes in light. The darker it gets, the larger your pupils get.

They expand for other reasons too. According to online sources and the voice of experience, pupils expand when people are sexually aroused and when they are completing complex cognitive tasks. Certain drugs—including illicit drugs—also make your pupils bigger.

Psychotropic drugs can have an obvious effect on the muscle groups in the eye and cause pupil dilation or mydriasis. Which muscle group is influenced depends on the type of drug one takes. Generally, pupil dilation can be caused by stimulants or really any drug that affects the adrenal glands.


Enlarged pupil/Image: FineArtAmerica

Drugs that cause the release of dopamine, a related neurotransmitter, can also cause one’s pupils to enlarge. Dvorsky notes: “Marijuana is a good example. Dopamine causes pupils to dilate by exciting the adrenergic receptors. “He adds: “(N)ot all drugs will produce the same degree of pupil dilation. For example, MDMA will have a much more profound effect on pupil dilation than, say, an antidepressant.”

Mind you, some drugs, such as opiates, will cause pupils to contract. That, however, is perhaps another column for another day.  Why do your pupils get larger when you’re on drugs?

Why do your pupils get larger when you’re on drugs?  Now you know.

You ask the questions.  We provide the answers.

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About Will Phoenix

W. Scott Phoenix, B.A., B.S. was born in Hawaii, raised in Pennsylvania and resides in California. He has been a published writer since 1978. His work has appeared (under various names) in numerous places in print and online including Examiner.com. He is a single parent of three children and has also worked as an actor, singer and teacher. He has been employed by such publications as the Daily Collegian and the Los Angeles Times.