Psychedelic Spotlight reports

A new report published in the journal Drug Science, Policy and Law has found that some people who used psychedelics recreationally were able to see and discern colors they hadn’t been able to before. Even more surprising, some said they experienced these vision improvements long after taking psychedelics.

Psychedelics like LSD (lysergic acid diethylamide) and psilocybin (magic mushrooms) are known to cause intensified sensory experiences, such as seeing colors more brighter and vividly. Swiss chemist Albert Hofmann, who first synthesized LSD, described the visual experience this way:

“Kaleidoscopic, fantastic images surged in on me, alternating, variegated, opening and then closing themselves in circles and spirals, exploding in colored fountains, rearranging and hybridizing themselves in constant flux…” 

Could psychedelics actually help the color blind see colors again? Researcher J.E.C. Anthony, with the University of Cambridge in the U.K., and colleagues, decided to find out. They analyzed responses to the 2017 edition of the Global Drugs Survey, a large-scale drug study conducted annually, that specifically asked color-blind individuals whether their vision had changed after taking a psychedelic.

A total of 47 survey respondents reported having some form of color vision deficiency. Roughly half (23) said they did experience improvements with their color blindness after taking psychedelics while the other half (24) said they did not. Those who did report improvements in color vision said those improvements persisted from three days to years after taking the medicine LSD and psilocybin were most often used by those surveyed, however other psychedelics were reported as well.

What caused these changes? Psychedelics are known to activate the 5-HT2A serotonin receptor, which promotes neural plasticity. This process enables the brain’s networks to make new connections through growth and reorganization. “Psychedelics may facilitate the experience of an expanded spectrum of colors,” the researchers suggested. “In the excited psychedelic state, new communication between cortical regions may link new photisms to pre-existing concepts of colors, thus facilitating a new color experience and improving color blindness.”

While the data is intriguing, researchers said the concept should be further investigated, possibly through more detailed surveys that specify which types of color blindness respondents have and what kind of improvements they experienced after taking the hallucinogens.



It is well documented that psychedelic drugs can have a profound effect on colour perception. After previous research involving psychedelic drug ingestion, several participants had written to the authors describing how symptoms of their colour blindness had improved. The Global Drugs Survey runs the world’s largest annual online drug survey. In the Global Drugs Survey 2017, participants reporting the use of lysergic acid diethylamide or psilocybin in the last 12 months were asked,    We have received reports from some people with colour-blindness that this improves after they use psychedelics. If you have experienced such an effect can you please describe it in the box below, say what drug you took and how long the effect lasted. We received 47 responses that could be usefully categorised of which 23 described improved colour blindness. Commonly cited drugs were LSD and psilocybin; however, several other psychedelic compounds were also listed. Some respondents cited that the changes in colour blindness persisted, from a period of several days to years. Improved colour blindness may be a result of new photisms experienced in the psychedelic state aligning with pre-existing concepts of colour to be ascribed a label. Connections between visual and linguistic cortical areas may be enhanced due to disorder in the brain’s neural connections induced by psychedelics allowing these new photisms and concepts to become linked. This paper provides preliminary data regarding improved colour blindness accompanying recreational psychedelic use which may be further investigated in future iterations of the Global Drugs Survey or in a stand-alone Global Drugs Survey-managed psychedelics survey.

‘Mescaline raises all colours to a higher power and makes the percipient aware of innumerable fine shades of difference, to which, at ordinary times he is completely blind’ (Huxley, 1954: 14).

I was completely astonished by the beauty of nature. Our eyes see just a small fraction of the light in the world. It is a trick to make a coloured [sic] world, which does not exist outside of human beings. – Albert Hofmann

These two quotes are a small fraction of the historical literature describing how psychedelics greatly alter one’s ordinary perception of colour. Such altered perception has been previously assessed in a lab controlled setting; finding changes in spectral patterns and hue discrimination, which also varies between different psychedelic drugs (Hartman and Hollister, 1963). This challenges our current understanding of the role of photoreceptors in central colour processing. However, restrictions around research involving these drugs made further studies into these phenomena more challenging.

We had received reports from several people who participated in our research that after taking a psychedelic, their previously colour-blind perception of the world was changed. One participant said,

All my life I suffered from red-dichromacy/protanopia … after psilocybin I viewed Monet’s San Giorgio Maggiore at Dusk, a painting which I had previously seen as a dull mass of brown and blue. All of the colours I was previously unable to see were there on the screen, and the emotion that I felt made me unable to speak for about half an hour.

Similar comments were made on online forums such as Reddit, ‘I’m colour blind, and I’m convinced shrooms [sic] allows me to see all colours vibrantly’ (Anonymous, 2015). These reports suggested that some individuals were experiencing improvements in their colour blindness.

Normal colour vision is trichromatic arising from comparisons between the differential excitement of three types of colour-sensing cone in response to certain wavelengths of light. Colour blindness is an inherited X-linked genetic disorder in which sufferers usually have one less cone type in the retina. This results in a reduced ability to compute spectral differences between certain colours depending on the wavelength of light the lost cone was most sensitive to. Psychedelics will not alter the inherent colour sensing ability of the optical machinery in the retina; however, they may affect central processing of the colour signal from the retina thus affecting colour blindness.

Previous studies have found that psychedelics can alter the way depressed patients respond to emotional faces, particularly fearful ones (Roseman et al., 2018), and a recent systematic review has highlighted that psychedelic use has been associated with permanent changes to personality in both the acute and long term (Bouso et al., 2018). This demonstrates the established potential of psychedelics to affect our central processing of emotion and we were interested as to whether psychedelics could assert similar effects by improving colour vision in colour-blind people.

Colour-blind synaesthetes have reported experiencing ‘alien’ photisms in relation to certain numbers (Ramachandran and Hubbard, 2001) showing that the brain can alter the colour experience beyond input from the optic nerve. A recent case study has reported a patient who has experienced synaesthesia for over seven years since ingesting 75–150 milligrams of 2C-B (Yanakieva et al., 2019), indicating that some psychedelic experiences can produce long lasting changes in perception. In both cases, the input to the brain from the sense organs is unchanged; however, it demonstrates the profound and persistent influence that central processing can have on the sensory experience.

The Global Drugs Survey (GDS) runs the world’s largest online drug survey and has been running annually since 2012. To address whether psychedelics improved colour blindness in recreational psychedelic users, a question was added to the Psychedelics section at the end of GDS2017 asking colour-blind participants if they had noticed changes in their colour blindness association with their use of psychedelics. The aim was to gather preliminary data regarding this phenomenon with the intention of exploring this further in future iterations of the GDS, if responses suggested changes occurred at a significant prevalence.

Data were compiled from the GDS. GDS has been running annually since 2012 (naming convention refers to year the data are released, not the year of collection) and runs the world’s largest annual online drug survey. The survey uses an anonymous cross-sectional design. The GDS2017 ran for seven weeks between the second week of November and end of December 2016 involving 119,075 participants after sample cleaning. Direct participant recruitment occurred through media partnerships in over 20 countries including outlets such as Vice, The Guardian and Zeit-on-Line, with secondary recruitment occurring via sharing of the content on social media such as Facebook or discussion forums such as Reddit (Barratt et al., 2017). Multi-institutional ethics approval was obtained from the Kings College London Research Ethics Committee 11671/001: Global Drug Survey, University of Queensland (No. 2017001452) and The University of New South Wales (HREC HC17769) Research Ethics Committees.

As part of GDS2017 a series of questions were included at the end of the Psychedelics section, to probe the effects of recreational use of psychedelics on colour blindness. Participants reporting the use of LSD or psilocybin in the last 12 months were asked,

We have received reports from some people with colour-blindness that this improves after they use psychedelics. If you have experienced such an effect can you please describe it in the box below, say what drug you took and how long the effect lasted.

The information obtained was received in the form of ‘open-ended’ qualitative anecdotes. The survey was translated into 14 main languages including German, Italian, French, Danish, Portuguese, Spanish, Hungarian, Flemish and Polish.

Responses were categorised as follows:

  1. Colour blind and colour change (EXPERIENCED)
  2. Colour blind and no colour change (NOT EXPERIENCED)


For a response to be marked ‘experienced’, the respondent had to imply a marked difference in ability to distinguish between colours; however, this effect didn’t have to extend beyond the period of intoxication. Since the question was asked, ‘If you have experienced such an effect’, implying both colour blindness and improvement, respondents weren’t required to positively identify as colour blind. Several respondents reported experiences of increased colour intensity; however, these were marked negative as this did not prove an increased ability to discern between colours.

An ideal ‘experienced’ response (ID 19670) was, ‘LSD, I’m red/green colour blind and the effect lasted the following 3 or 4 days’.

An ideal ‘not experienced’ response (ID 13385) was, ‘I have deuteranopia, but unfortunately I didn’t sense any change in my colour perception on psilocybin. (I also figured this out using example images for people with colour blindness)’.

Graphs were constructed using RStudio (RStudio Team, 2019).

The question received 382 responses from 10 different countries of which 47 responses could be categorised with regards to the question. Of the categorised responses, 23 experienced and 24 didn’t experience improved colour blindness symptoms (Figure 1). Despite the low number of categorised responses, there was a sufficient number of respondents reporting improved colour blindness to suggest that, in some people, recreational psychedelic use may improve colour blindness.


Figure 1. Graph showing the number of respondents reporting about changes to their colour blindness following recreational psychedelic use. Experienced means respondents reported improved colour blindness, not experienced means respondents did not report improved colour blindness.

We were interested in whether the specific psychedelic drug used would influence the prevalence of improved colour blindness being experienced. Of the 23 respondents who experienced the effect, 15 indicated the drug used, with some indicating multiple drugs. LSD and psilocybin mushrooms were the most commonly cited psychedelic drugs (Figure 2). There were single mentions of novel psychedelic substances used with which this effect occurred. This included substituted 2C family drugs such as 25I-NBOMe and 2C-C and several novel substituted tryptamines such as 5-MeO-DMT and 4-HO-MET. Responses did not indicate that a specific drug induced changes in colour blindness with a greater frequency than other drugs.


Figure 2. Graph showing the number of times certain drugs were cited to improve colour blindness symptoms. The ‘other’ category includes substituted 2C family drugs and novel substituted tryptamines. Some respondents listed multiple drugs. LSD: lysergic acid diethylamide.

The question also asked about the length of time the changes in colour blindness lasted for. Of respondents who experienced changes in their colour blindness, 39% indicated that their changed perception continued for a period after the drug had worn off ranging from three days to ‘years’. The time frames given for persistence of this phenomenon beyond the immediate effects of the drug were largely non-specific and further quantification was not possible due to the nature of the responses given.

This study explored the effects of recreational psychedelic use on colour blindness through a self-reported survey question included in GDS2017. There were 382 responses to the question of which 47 could be categorised. Of these, 23/47 reported experiencing improved colour blindness relating to recreational psychedelic use, defined as an improved ability to discriminate between colours. Respondents reported a range of drugs and time frames associated with improved colour vision. The number of respondents reporting improved colour blindness suggests that such improvements do occur in a proportion of recreational users of psychedelics. Psychedelics may facilitate the experience of an expanded spectrum of colours. In the excited psychedelic state, new communication between cortical regions may link new photisms to pre-existing concepts of colours, thus facilitating a new colour experience and improving colour blindness. The self-reported anonymous nature of the GDS made it hard to verify claims and the 20–30 minutes length of the survey meant responses to this question, placed at the end, may have been affected by participant fatigue, thus reducing their quality and utility. In the future, we plan to run a more in depth GDS managed psychedelics survey to further gather reports regarding this phenomenon.

Psychedelics do not alter the innate nature of the visual signal from the retina because the defect is of genetic origin – the result of fewer ‘colour-sensing’ cones in the retina. The signal sent to the primary visual cortex from the retina likely remains unchanged under the influence of psychedelics. Colour signals are then processed, via the ventral visual pathway, in the V4 region of the occipital cortex and it is from this point that psychedelics may affect higher order processing and ultimately perception of colour. Psychedelics may result in new colours being experienced, termed ‘alien’ photisms. In the psychedelic state, increased neural plasticity may aid the formation of associations between new photisms and pre-existing concepts of colours that were not previously distinguished, thus improving the range of colours experienced and improving colour blindness.

Classical psychedelics, such as LSD and psilocybin, are 5-HT2A receptor agonists (Glennon et al., 1984); however, each psychedelic drug has its own unique binding profile, particularly regarding other 5-HT receptor subtypes (Ray, 2010). These differences may affect the extent to which different psychedelic drugs can improve colour blindness; however, the nature of the responses provided did not allow such analysis. Despite the variation in binding profiles, most psychedelic drugs principally agonise the 5-HT2A receptor. Agonism at this receptor depolarises deep-layer pyramidal neurons in the prefrontal cortex (Andrade, 2011) resulting in disordered signalling and a window of increased neural plasticity, described by Carhart-Harris et al. (2014) as the ‘Entropic Brain Hypothesis’. The period of increased uninhibited cortical signalling induced by modulation of the 5-HT2A receptor may enable new neural connections to form. Psilocybin, a classical psychedelic, has been shown to increase the formation of homological scaffolds of brain functional networks under fMRI analysis (Petri et al., 2014) and such changes in brain chemistry may persist beyond the immediate pharmacological actions of the drug (Carhart-Harris and Nutt, 2017). We propose that the new neural networks may enable new associations between the perceived and linguistically known colour of objects, altering the experience of colour perception.

Under the influence of psychedelic drugs, users may experience an expanded array of colours, possibly as a result of enhanced entropy in the V4 cortex leading to over-exaggerated cross visual field comparisons. This does not necessarily mean the colours seen of objects are more representative of their true colour, merely a wider variety of colours are experienced (Hartman and Hollister, 1963). Some of the colours experienced in this state may be entirely new to the user. Colour blind synaesthetes have reported experiencing ‘alien’ photisms, which are reported to not exist within the range of their normal perception, in relation to certain numbers (Ramachandran and Hubbard, 2001), showing the ability of the brain to alter the experience of colour beyond optic nerve input. Thus, the notion of a new colour being experienced under the influence of psychedelic drugs is not unfathomable.

The ‘alien’ colours experienced whilst under the influence of psychedelic drugs may become ascribed to objects based upon known linguistic ideas of any object, for example an apple is red or the sky is blue. Despite having difficulty distinguishing these colours, depending on the type of colour blindness, individuals still have a concept of these colours. Congenitally blind children have been shown to have a 69–80% agreement in associations of colours relative to their sighted counterparts. For example, yellow may be conceptualised as a ‘happy, nice, shiny colour’. It was shown that these concepts of colour were purely language based and relied on being taught their associations (Anthony, 1996). Alien colours experienced in the psychedelic state may align with the colour-blind user’s conceptual understanding of a colour they are not normally able to observe. This may be ascribed to certain objects leading to lexically driven changes in the perception of specific objects in line with their colour. Such changes would be unlikely to occur universally or consistently due to different colour associations between individuals coupled to different sets and settings.

Synaesthesia may be traditionally be thought of as ‘seeing sound’ or mixing of traditional special senses; however, there are a plethora of other inducer-concurrent associations (Luke and Terhune, 2013). There are a variety of explanations for the phenomenon of synaesthesia including increased neural connectivity in the psychedelic state (Petri et al., 2014) or cortical disinhibition and hyperexcitability (Yanakieva et al., 2019). It is feasible that increased connection between regions of the cortex responsible for higher colour perception, V4, to concepts of colour in language centres may occur in the psychedelic state through ‘noisy’ disordered signalling. New connections between these aforementioned areas of association cortex complement Whorfian ideas of colour discrimination which may affect an individual’s perceptions of coloured objects, consequently leading to the improvement of colour discrimination in the colour blind.

There is a growing body of evidence to suggest serotonergic hallucinogens can affect recognition of facial expressions (Rocha et al., 2019). LSD has been shown to reduce recognition of sad or fearful faces alongside enhancing emotional empathy (Dolder et al., 2016). In a different study, the day after a 25-milligram psilocybin treatment, enhanced amygdala responses to emotional faces, particularly fearful ones, were found, suggesting alterations in the manner in which depressed patients respond to emotional stimuli (Roseman et al., 2018). The brain contains concepts of emotions and if the response to emotional stimuli and their associations in the brain can be altered it is plausible that our associations of colours and thus their perception can be changed too, particularly because the raw visual signals entering the brain in the cases of recognising facial expression and processing colour are constant.

Long term changes in colour blindness, lasting beyond psychedelic experience, were reported by 39% of respondents. This would suggest that such effects are likely to be common in a larger proportion of the colour-blind population. However, the number of colour-blind respondents not experiencing this was likely underreported due to the positive nature of the question and thus this high proportion is likely an artefact of the wording. A possible reason for the persistence of changes in colour vision could be the extra-pharmacological effects of psychedelics such as set and setting, which likely vary between respondents, producing lasting changes in neural networks (Carhart-Harris and Nutt, 2017). Dosage may also account for this as levels of 5-HT2A receptor occupancy have been shown to correlate with the intensity of effects experienced (Madsen et al., 2019) which may complement the extra-pharmacological effects. However, the design of the GDS study makes it difficult to control for these factors. There are recorded instances of psychedelic-induced visual perceptual changes persisting. Hallucinogen persisting perception disorder is estimated to have an occurrence of 1/50,000 in regular users of psychedelic drugs (Halpern et al., 2016) and some case studies have reported symptoms lasting for months or years (Martinotti et al., 2018). Recently, a case of acquired synaesthesia was reported in a 29-year-old male following the use of 2C-B which had persisted for over seven years (Yanakieva et al., 2019).

This study found that a proportion of colour-blind participants reported improved colour blindness following the recreational use of psychedelics, defined as an improved ability to discern between colours. There are several limitations to the study. The data consisted of self-reported anecdotes of variable quality, some of which proved hard to interpret, thus making accurate quantification and standardised interpretation difficult. The reports were self-validated both as to the nature of the colour blindness and whether this phenomenon was experienced. Colour blindness is not a unimodal disorder and different forms of colour blindness may have been affected differently. We were unable to obtain this level of detail with the responses given. The question was asked in a ‘special section’ at the end of GDS2017 which itself takes 20–30 minutes to complete and number of usable responses was small, 47/382. Some responses didn’t relate to the question or were too difficult to decipher, which may reflect participant fatigue. Language barriers were unlikely to play a role due to the wide variety of language translations available.

In future iterations of the GDS, we plan to revisit this exploratory study and more clearly identify the nature of pre-existing colour vision deficit and more specifically assess changes in visual perception, the drug taken and better quantification of the persistence of the effects. Rather than a free-text response, participants could provide answers in a multiple-choice format with the question deconstructed into discrete parts. Due to the length of the standard GDS, a GDS managed stand-alone psychedelics survey may be more suitable to minimise participant fatigue. This would enable a variety of phenomena regarding recreational use of psychedelics to be evaluated, not just colour perception, such as visual acuity which was mentioned by several respondents.

The authors would like to thank the participants of the GDS2017 for giving their time to complete the survey and making this study possible. They are grateful to Sophia West for her help in translating the responses into English.

Declaration of conflicting interests
The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: A Winstock is the owner and founder of Global Drug Survey (GDS). Global Drug Survey Ltd is an independent self-funded organisation.

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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