Marijuana Lowered Eye Pressure, but Only in Users Who Felt Relaxed | Research

The takeaway

Smoking marijuana reduced eye pressure in light-to-moderate users, but only in those who experienced a substantial high and relaxation, suggesting the effect may be indirect.

Read this if you have heard that marijuana helps glaucoma and want to understand what early research actually showed.

12 mg THC
reduced eye pressure, but only in users who felt relaxed

What the researchers found

After smoking a dose of marijuana containing 12 mg of THC, normal eye pressure decreased in light-to-moderate users. The pressure reduction occurred only in participants who reported experiencing a substantial high and a state of peaceful relaxation.

This pattern suggested the eye pressure lowering was an indirect effect tied to the relaxation state rather than a direct pharmacological action of THC on the eye. The researchers noted that similar relaxation from non-drug sources could theoretically produce the same result.

Why it matters

Marijuana is often cited as a potential glaucoma treatment. This early study complicated that narrative by suggesting the eye pressure reduction might stem from generalized relaxation rather than a direct drug effect on the eye, raising questions about whether cannabis offers any specific advantage over other relaxation methods for lowering intraocular pressure.

The numbers in context

- Dose: 12 mg THC delivered via marijuana cigarette

- Eye pressure reduced in light-to-moderate users

- Effect occurred only in participants reporting substantial high and relaxation

- No reduction observed in users who did not achieve relaxation

How the study worked

Participants smoked a marijuana cigarette delivering 12 mg of THC, and intraocular pressure was measured. The relationship between subjective drug effects (high, relaxation) and pressure changes was analyzed.

What this study cannot tell us

The abstract does not report exact sample size or the magnitude of pressure reduction. Only one dose level was tested. The study examined only immediate effects, not long-term glaucoma management. The indirect mechanism hypothesis (relaxation) was not tested against a relaxation-only control.

How to read the evidence

Small observational study without a true control group. The indirect mechanism hypothesis was not formally tested.

When this study was published

Published in 1975. An early study on cannabis and intraocular pressure. Modern ophthalmology has largely moved past cannabis as a viable glaucoma treatment.

The bigger picture

This study foreshadowed a debate that continues today. While cannabis does lower intraocular pressure, the effect is short-lived (typically 3-4 hours), and modern ophthalmology generally does not recommend cannabis for glaucoma because of its brief duration and psychoactive side effects compared to conventional eye drops.

Questions still open

Would THC lower eye pressure in someone who does not experience relaxation from it?
How does the duration of cannabis-induced pressure reduction compare to standard glaucoma medications?

Read the original research

Marijuana smoking and reduced pressure in human eyes: drug action or epiphenomenon?

Investigative ophthalmology, 14(1), 52-5

View on PubMed ↗

Citation

Flom, M C; Adams, A J; Jones, R T. (1975). Marijuana smoking and reduced pressure in human eyes: drug action or epiphenomenon?. Investigative ophthalmology, 14(1), 52-5.