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Consuming Psychedelics Temporarily Improves Man's Color Blindness

An Ishihara test
Ishihara tests, like this one, hint at the presence or absence of functioning color vision. What number can you see? Answer at the bottom! Credit: Public domain

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There’s a strong link between psychedelic drugs and our vision. Trippy details, unexpected saccades and pupil dilation are all linked to taking compounds like LSD, magic mushrooms and DMT. But a new case report may be the first detailed documentation of a psychedelic temporarily reversing a diagnosis of color blindness.


The report, published in the journal Drug Science, Policy and Law, details the experiences of a 35-year-old man who had been diagnosed with a mild case of red-green color blindness five years earlier. The findings are limited by confounding factors, including the participant’s self-reported data and voracious appetite for psychoactive drugs.

Testing color blindness

Color blindness is a congenital condition caused by gene mutations that change structures in our eyes called cones. These are structures that detect light and convert it into a signal that can be read by the brain. Cones contain pigments that respond to one of red, green or blue light. Some people lack one of these cones entirely. Those with the most common form of color blindness, deuteranomalia, possess all three cones, but have defects in one of them. This type of color blindness is linked to a mutation on the X-chromosome and so affects far more men than women. 1 in 20 men are thought to have deuteranomalia.


Color blindness can be tested for using the Ishihara test – consisting of plates showing shapes patterned and colored to reveal numbers. People with normal vision score highly on these tests, while a lower score indicates increasingly severe color blindness.


The subject of this case study self-administered the Ishihara test prior to taking a large 5 g dose of psilocybin-containing mushrooms. Out of 21 plates in the test, the subject scored 14, which indicates a mild color blindness. A score above 17 indicates normal vision. While our mushroom-munching protagonist’s score only slightly inched up to 15 when he retested himself 12 hours later, waiting a further 12 hours bumped his score up to 18, indicating normal, although not perfect, color vision. Importantly, he refrained from looking at the answers to the test, only reviewing his scores four months later after multiple subsequent tests. The subject’s top result was achieved eight days after administration, when he recorded a 19. At the four-month timepoint, the subject’s recorded scored remained at 18.


The research team brought the subject into their lab to administer him with an Ishihara test themselves. At this point, his initial massive psilocybin dose had occurred more than a year previously – although he had taken a second dose four months prior to his lab visit. Here, he scored a 16, which once again suggested he was slightly colorblind.

Psychedelics can’t change your genes

Psilocybin is thought to have effects throughout the brain, including in the nerves that link our eye to our brain and in the brain regions that process vision. Researchers think that psychedelics’ changes to our vision are likely to be caused by alterations in brain activity. Even the most enthusiastic psychedelic disciple has yet to find evidence that taking these drugs can modify our DNA sequence, so it’s not surprising that the effects of psilocybin on color blindness are modest and temporary. But the fact that any change was observed, and for a prolonged period, write the authors, “raises important questions about the possibility of psilocybin inducing durable alterations in visual processing in some people.”


Future studies, they note, should involve a large number of patients with color blindness, be evaluated in a lab and use various alternate Ishihara plates to avoid any effect of repeatedly using the same test to assess vision.


The authors also note some substantial limitations to the conclusions that can be drawn from this case report, including the reliance on self-administered testing. Additionally, the participant in the current case study took an unusually broad range of psychoactive substances – including weekly cannabis, an LSD microdose and a blast of nasal esketamine – that may complicate interpretations of his score. We’ll need more data to see whether psychedelics can truly add color to your world.


Reference: Barnett BS, Sweat NW, Hendricks PS. Case report: Prolonged amelioration of mild red-green color vision deficiency following psilocybin mushroom use. Drug Science, Policy and Law. 2023;9:20503245231172536. doi:10.1177/20503245231172536


Ishihara Test Answer: 74

Meet the Author
Ruairi J Mackenzie
Ruairi J Mackenzie
Senior Science Writer
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