Marijuana Lowered Eye Pressure, but Only in Users Who Felt Relaxed
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.
Quick Facts
What This Study 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.
Key Numbers
- 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 They Did This
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.
Why This Research 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 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.
What This Study Doesn't 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.
Questions This Raises
- ?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?
Trust & Context
- Key Stat:
- 12 mg THC reduced eye pressure, but only in users who felt relaxed
- Evidence Grade:
- Small observational study without a true control group. The indirect mechanism hypothesis was not formally tested.
- Study Age:
- Published in 1975. An early study on cannabis and intraocular pressure. Modern ophthalmology has largely moved past cannabis as a viable glaucoma treatment.
- Original Title:
- Marijuana smoking and reduced pressure in human eyes: drug action or epiphenomenon?
- Published In:
- Investigative ophthalmology, 14(1), 52-5 (1975)
- Authors:
- Flom, M C(2), Adams, A J(2), Jones, R T(4)
- Database ID:
- RTHC-00004
Evidence Hierarchy
Watches what happens naturally without intervening.
What do these levels mean? →Read More on RethinkTHC
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Cite This Study
https://rethinkthc.com/research/RTHC-00004APA
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.
MLA
Flom, M C, et al. "Marijuana smoking and reduced pressure in human eyes: drug action or epiphenomenon?." Investigative ophthalmology, 1975.
RethinkTHC
RethinkTHC Research Database. "Marijuana smoking and reduced pressure in human eyes: drug a..." RTHC-00004. Retrieved from https://rethinkthc.com/research/flom-1975-marijuana-smoking-and-reduced
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.