Neurophilosophy

DEPRESSION has long been associated with vision – and to colour perception in particular – and the link between them is evident in everyday language. Depression is, of course, often referred to as “feeling blue”, and those who suffer from it are sometimes told to “lighten up”. The link can be found in art, too – Picasso’s so-called “Blue Period“, for example, which was brought on by the suicide of his close friend Carlos Casagemas, is characterised by a series of striking paintings in shades of cold blue, which express the deep melancholy he felt at the time.

Although the association between depression and colour is largely metaphorical, there is actually some evidence that they are closely linked. The most recent comes from a new study by German researchers published in the journal Biological Psychiatry. The study shows that depressed people have reduced sensitivity to contrast, and therefore that they may perceive the world differently from others. It also suggests that depression can be diagnosed by objective measurements of electrical activity in the eye.

Earlier work has already shown that there is a physiological link between depression and vision. It has long been known, for example, that reserpine, a drug which is prescribed for psychosis and hypertension and which induces depression in humans, causes excessive sensitivity to light in various animals. Other studies have shown that patients with major depressive disorder (MDD) may also be supersensitive to light and that this can be reversed by anti-depressants; that depression causes changes in the electrical activity of the brain in response to visual stimuli; and that this change in activity can be altered by antidepressants.

Last year, neuropsychiatrist Ludger Tebartz van Elst of the University of Freiburg and his colleagues reported that patients with MDD exhibited a reduced sensitivity to contrast, while a team of researchers from Yale showed that visual motion perception is enhanced in depression. But these experiments could not establish whether the observed changes were due to alterations in the retina or the various parts of the brain through which visual information travels and is processed. And because they were based on the conscious experiences of the participants, the reported effects could have been modulated by attentional or other mechanisms.

For their latest study, van Elst’s group sought to confirm their previous findings using objective methods, and to determine if any observed changes in the contrast sensitivity of depressed patients are due to changes in the eye or brain. They recruited 40 patients diagnosed with MDD and 40 matched, healthy controls. They presented the participants with visual stimuli consisting of black and white checkerboard patterns, and used pattern electroretinography (PERG) to measure the response to the patterns. The PERG is evoked by viewing patterned stimuli and, in this case, its size is indicative of contrast gain. It is recorded at the cornea, and is thought to represent the activity of the retinal ganglion cells, which are involved in the early processing of visual information and whose axons form the optic nerve that carries the information into the brain.

Specifically, the researchers looked for differences between the two groups of participants in activity reflecting contrast gain, the process by which cells in the retina adapt to variance in the light intensity of the visual scene so that the amount of information extracted from it can be maximized. They found a significant difference in the contrast gain-related activity between the depressed patients and controls. The participants diagnosed with depression displayed a marked reduction in contrast gain when compared with the controls. The reduction was observed in both medicated and unmedicated patients. Those taking medication for their depression, however, had slightly lower depressivity scores and correspondingly better contrast gain than unmedicated patients.

Furthermore, the reduction in contrast gain was strongly correlated with the severity of depression – the more severe the depression, the greater was the observed reduction in contrast gain. No difference was observed between patients with recurrent depression and those experiencing their first episode of the condition, or between depressed patients taking selective serotonin uptake inhibitors such as fluoxetine (Prozac) and those taking tricyclic antidepressants such as imipramine. The intensity of the treatment, or dose being taken, did not affect the reduction in contrast gain observed in the depressed patients. Finally, the researchers could predict, with an accuracy of greater than 90%, which of the participants had been diagnosed with depression on the basis of their electroretinographic recordings.

This is a pilot study whose results need to be replicated. Nevertheless, it shows that processing of visual information related to contrast is altered in the retinae of depressed patients. A likely consequence of this is a reduced ability to perceive contrast – depressed people may indeed experience the world as being less colourful. The study further suggest that PERG could be useful in diagnosing and objectively measuring depression. It’s still unclear, however, whether reduced contrast processing is a specific marker of depression. The same effect could possibly occur in patients with other neuropsychiatric conditions such as schizophrenia, and this is could be investigated in future work.   


Bubl, E., et al. (2010). Seeing Gray When Feeling Blue? Depression Can Be Measured in the Eye of the Diseased. Biol. Psychiatry 68: 205-208. DOI: 10.1016/j.biopsych.2010.02.009.

Comments

  1. #1 Laborious
    July 22, 2010

    Neat study. The germans are great at science, but I know that a good chunk of dyslexics, ADHD, AS people have hyper sensitivity to light, and other thing’s like that. So I would speculate that the study is good but might not be for all people. I would even speculate that the study is more for NT/NP (neuro typical/normal people) types. Cool study though, I hope they do more study’s into this area soon, with larger swabs of group types for a more accurate correlation of data. Also more variations of the color/differentiation test’s to get even better data analysis. Oh well just my 2 cent’s for the kettle. :)

  2. #2 Andrew Smith
    July 22, 2010

    I wonder if color blind people are more prone to depression.

  3. Fascinating study – thanks for posting it.

    I’m a therapist and neurofeedback provider. I’ve had more than one depressed client make comments, as they’re starting to feel better, like, “The world has more color now” or “When I go for a walk I’m seeing more details.” The latter is not as directly relevant perhaps but contrast may be a factor.

    So interesting!

  4. #4 Fred McVittie
    July 23, 2010

    Interesting stuff. I’m just being glancing at material related to the possible evolutionary origins of (non-clinical) depression, specifically depressive behaviour as evolutionarily adaptive. Do you think this contrast reducing feature of the condition could be part of this?

  5. #5 Tharin
    July 23, 2010

    This can also be related to Seasonal Affective Disorder – people with less sensitive light perception could be influenced more strongly by the lack of daylight.

  6. #6 Cary Enoch Reinstein
    July 23, 2010

    This concept is very fascinating to me since I observed–but only after reading this article–that there’s an inverse correlation in the art that I make. The last couple of weeks I’ve been creating very bright paintings with lots of yellows and greens. Nevertheless, my mood is definitely “blue” though that color barely appears in any of my recent work. My medical diagnosis is Schizoaffective Bipolar. I’m also dyslexic. It’s all but impossible to determine if my ADHD is either comorbid with dyslexia, which is common, or merely mood triggered. See my website for art examples especially in the Pathways” gallery. All of those were done while manic.

  7. #7 Shatterface
    July 23, 2010

    Isn’t scoptic sensitivity syndrome – common among dyslexics – a hypersensitivity to contrast? I used to use coloured paper in correspondence with a dyslexic colleague in order to reduce contrast and she used to alter the settings on her PC to make text easier to read.

  8. #8 Ania
    July 27, 2010

    I think that the most important issue for depression is how to prevent it, not how to treat it. People are concentrated too much on how to treat it, instead of finding out what make those people to fall into this illness.

  9. #9 Crazy Mermaid
    July 28, 2010

    While I was psychotic (diagnosed bipolar disorder with psychotic tendencies), all of the colors were way more vivid. A psychedelic green snakeskin wallet that I purchased while psychotic had faded out to a murky green when I looked at it after my release from my three week stay at the mental hospital. I’ve been told by people who took LSD and other drugs of that type that they experienced the same kind of vivid color sensation as I did while they were high. I’d like to see some research on this.

  10. #10 Dirk Hanson
    July 30, 2010

    I’ve heard positive SSRI responders say that the world literally got brighter for them. Enhanced chromatic contrast?

  11. #11 Chris Phoenix
    August 2, 2010

    I have some reasons to suspect dyslexia may be related to flakiness of the magnocellular system, which affects timing. The parvocellular system, which is used for visual detail, may improve to compensate. This may be relevant to some of the earlier comments on visual contrast and detail.

    The magnocelluar system affects more than just vision, which may explain why dyslexia can affect vision, hearing, balance, and time sense.

    Chris

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    August 22, 2010

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  13. #13 Bobby
    August 22, 2010

    Very interesting study..I wonder whether there is a relation between colour blindness and depression. I would be really interested in results.

  14. #14 E Wolke
    September 8, 2010

    Interesting. Brings to mind Churchill’s “Black Dog”, what he used to call his periods of depression. As a depressive myself, I can report anectdotally that bright colors make me feel better (say, wearing a bright shirt or scarf) and that looking at good art or hearing good music is also a tonic. Has anyone done work with hearing, especially music?

  15. #15 Mo
    September 8, 2010

    @E Wolke: According to this 2008 Cochrane review, “studies suggest that music therapy for people with depression is feasible and indicate a need for further research.”

  16. #16 David rudloff
    November 3, 2010

    It would be interesting to better understand the relationship of visual contrast to perception. It sounds as though that reduced gain may be related to reduced visual scanning for objects, particularly in low light situations. Such a condition clearly has implications for certain occupations, safety, and various activities.
    For instance, could it be related to a batting slump or judging errors related to oncoming traffic? How about reading speed for various fonts?
    Another question is whether a history of bright light intolerance is of diagnosticstatistical use in evaluating complaints possibly related to depression.

  17. #17 william bauske
    December 8, 2010

    i just recently increased my vitamin d intake to 8000 iu a day, and experienced an increase in color perception, with redder reds and purpler purple, etc. As well as a more even mood. we might all agree that the sun increases everyones mood, vitamin d production from the sun may be why. It was a suspician of mine that perhaps picasso got very little sunlight and that alone could explain his reported moods, low and behold on wiki it stated he slept during the day and worked at night. chances are good that vitamin d plays a major role in depression.