Posted by tags: researchblogging.org, bipolar disorder, manic-depressive illness, unipolar depressive disorder, clinical depression, seasonal affective disorder, SAD, circadian clock, light therapy
“Starry Night” (1889) is an oil painting by Dutch post-impressionist artist Vincent van Gogh. It was added to the permanent collection of the Museum of Modern Art (MoMA) in New York City in 1941. [wallpaper size].
According to a “NewsFocus” article that appeared in last Friday’s Science, there is a move afoot to use light therapy and sleep deprivation to help the body’s circadian clock reset and maintain itself in those people who suffer from bipolar disorder. This treatment option has already been used with people who suffer from depression, especially depression that occurs in the autumn and winter months, when daylength is growing shorter. This form of depression is known as “Seasonal Affective Disorder” or SAD.
How is SAD mediated in the body? It is well-documented that the body’s master clock resides in the suprachiasmatic nucleus of the brain. This biological clock regulates changing concentrations of numerous hormones and proteins in the body over an approximately 24-hour cycle. Additionally, the concentrations of many of these neurochemicals change during the course of the day, particularly that of melatonin, which is secreted in the highest concentrations by the pineal gland when it is dark, and also that of serotonin, whose levels are boosted as the result of exposure to sunlight. Serotonin is a neurotransmitter that is associated with the feeling of well-being.
Basically, humans begin secreting melatonin in the evening to prepare the body for sleep. Previous studies had shown that people with SAD who were exposed to bright morning light showed improvement while those who experienced bright evening light did not. Additionally, people with SAD whose circadian rhythyms lagged behind a normal 24-hour sleep-wake cycle that took melatonin in the late afternoon experienced improvement in their mood while those who received melatonin in the mornings did not. On the other hand, this same treatment regimen had the opposite effect in those people whose sleep-wake cycle was advanced from normal (see figure, below).
According to the article, recent research has shown that people who suffer from mood disorders other than depression, and from thought disorders such as schizophrenia, may also be experiencing disruptions to their circadian clocks. For example, a study by Vishwajit Nimgaonkar that was published two years ago in Chronobiology International proposed that people with bipolar disorder had disturbed biological clocks, based on survey information that probed their activity and sleep patterns.
But most convincing to me are the genetic studies that appear to support these circadian rhythym survey data. In a series of elegant experiments, Colleen McClung and her colleagues at the University of Texas Southwestern Medical Center in Dallas created mice that were missing the Clock gene. This gene encodes a key protein that is an integral part of the circadian system. Clockless mice became hyperactive and were more likely to take risks — manic behavior. Further, the researchers found that expressing the CLOCK protein in the animals’ midbrains rescued these mutant mice, effectively restoring their behavior to normal, as they reported in their paper published in the Proceedings of the National Academy of Sciences on 10 April 2007 (read more about this).
Interestingly, an ongoing study led by Anna Wirz-Justice of the Centre for Chronobiology at the Psychiatric University Clinic in Basel, Switzerland, seems to show that patients with schizophrenic disorder and borderline personality disorder also experience abnormal circadian rhythyms. Also, psychiatrist Namni Goel of the University of Pennsylvania recently presented her data at the meeting for biological clocks and rhythms at Cold Spring Harbor Laboratory in New York state showing that many 24-hour hormonal rhythms in patients with night eating syndrome were either advanced or delayed with respect to a normal sleep-wake cycle.
Light therapy has traditionally been viewed with suspicion. According to the article, even a few years ago, “people looked at us as if we were some kind of strange witch healers,” says Benedetti, who began combining light therapy with sleep deprivation in the 1980s.
But the psychiatric community is starting to come around to the potential benefits of light therapy. For example, in 2005, a group led by Robert Golden of the American Psychiatric Association examined the efficacy of light therapy by conducting a meta-analysis of published literature. They concluded that light treatment significantly reduced the depressive symptoms of SAD, as well as those of other mood disorders.
But funding for light research has not been forthcoming, mainly because the community sees antidepressants as being effective. However, antidepressants are not always effective or even recommended for everyone, especially for pregnant or nursing women.
Unfortunately, based on my own experience, altering the body’s circadian clock is not necessarily always effective. My own body clock is apparently not affected by light therapy, even though I did use it (in the mornings only) for nearly one year when in graduate school. At that time, I did not experience any change in mood, although I did end up getting a lot of reading done. Curiously, my own episodes of mania and depression appear to only vaguely track daylength changes (but I also experience “rapid mood cycling” which makes for a more complicated picture overall).
On one hand, perhaps I am like those poor Clockless mutant mice, and thus, unable to respond to light manipulation? But on the other hand, and based on what I read in this article, it is also possible that my own circadian clock cycles with a longer rhythym than 24 hours, which the article’s author says is relatively unusual. Although, considering that my moods cycle rapidly, I am not convinced that I have a longer circadian cycle than 24 hours. Because it is known that exposure to bright lights in the evening can reset a slow cycling circadian clock, it is possible that this might effectively reset my own biological clock (unfortunately, I no longer possess that light box, nor any bright lights, so I cannot test this hypothesis now).
However, despite my own reservations about light therapy, I still think that it is worth investigating, especially for those of you who know that you experience seasonally-related changes in your mood. Further, many people suffering from a mood disorder tend to resist using medications for a variety of valid reasons, particularly due to the side-effects — and light does not have any known side-effects, except potentially, an elevation in mood and perhaps an increased amount of reading.
Source
“Is Internal Timing Key to Mental Health?” By Ryudhijit Bhattacharjee. Science 31:1488-1490 (14 September 2007)
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