Seasonal Affective Disorder May Be Linked to Genetic Mutation, Study SuggestsNovember 04, 2008With the days shortening toward winter, many people will begin to experience the winter blahs. For some, the effect can be devastating. About 6 percent of the U.S. population suffers from seasonal affective disorder, or SAD, a sometimes-debilitating depression that begins in the fall and continues through winter. Sufferers may even find it difficult to get out of bed in the morning. The disorder, which is not well understood, is often treated with "light therapy," where a SAD patient spends time each morning before a bank of bright lights in an effort to trick the brain into believing that the days are not so short or dim. A new study indicates that SAD may be linked to a genetic mutation in the eye that makes a SAD patient less sensitive to light. "These individuals may require brighter light levels to maintain normal functioning during the winter months," said Ignacio Provencio, a University of Virginia biology professor who studies the genetics of the body's biological clock, or circadian rhythms. Provencio and his colleagues have discovered that melanopsin, a photopigment gene in the eye, may play a role in causing SAD in people with a recently discovered mutation. "We believe that the mutation could contribute to increasing the amount of light needed for normal functioning during winter for people with SAD," Provencio said. "Lack of adequate light may be a trigger for SAD, but not the only explanation for the disorder." The findings are published in the online edition of the Journal of Affective Disorders, and will appear later in the print version. The study was conducted with several other institutions, including the National Institute of Mental Health. It involved 220 participants, 130 of whom had been diagnosed with SAD and 90 participants with no history of mental illness. Using a genetics test, the study authors found that seven of the 220 participants carried two copies of the mutation that may be a factor in causing SAD, and, strikingly, all seven belonged to the SAD group. "While a person diagnosed with SAD does not necessarily carry the melanopsin mutation, what we found strongly indicates that people who carry the mutation could very well be diagnosed with SAD," Provencio said. "We think that if an individual has two copies of this gene, he or she has a reasonable chance of having the disorder." The researchers found that a person with two copies of the gene is five times more likely to have symptoms of SAD than a person without the mutation. "That is a very high effect for a mental illness, because most mental illnesses have many potential causes," Provencio noted. "A mental illness may arise from many mutations, and we have found one that has a clear link." The melanopsin gene encodes a light-sensitive protein that is found in a class of photoreceptors in the retina that are not involved with vision, but are linked to many non-visual responses, such as the control of circadian rhythms, the control of hormones, the mediation of alertness and the regulation of sleep. The mutation in this gene may result in aberrant regulation of these responses to light, leading to the depressive symptoms of SAD. About 29 percent of SAD patients come from families with a history of the disorder, suggesting a genetic or hereditary link. "The finding suggest that melanopsin mutations may predispose some people to SAD, and that if you have two copies of this mutation, there is a very high probability that you will be afflicted," Provencio said. "An eventual understanding of the mechanisms underlying the pathological response to light in SAD may lead to improved treatments." Provencio added that the finding, with further study, could also lead to improved testing for SAD. Provencio's colleague and lead author in the study is Kathryn Roecklein, an assistant professor of psychology at the University of Pittsburgh. University of Virginia |
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| Related Seasonal Affective Disorder Current Events and Seasonal Affective Disorder News Articles Vitamin D may not be the answer to feeling SAD A lack of Vitamin D, due to reduced sunlight, has been linked to depression and the symptoms of Seasonal Affective Disorder (SAD), but research by the University of Warwick shows there is no clear link between the levels of vitamin D in the blood and depression. When it comes to sleep research, fruit flies and people make unlikely bedfellows You may never hear fruit flies snore, but rest assured that when you're asleep they are too. According to research published in the January 2009 issue of the journal GENETICS, scientists from the University of Missouri-Kansas City have shown that the circadian rhythms (sleep/wake cycles) of fruit flies and vertebrates are regulated by some of the same "cellular machinery" as that of humans. Bright lights, not-so-big pupils A team of Johns Hopkins neuroscientists has worked out how some newly discovered light sensors in the eye detect light and communicate with the brain. The report appears online this week in Nature. PET scans help identify mechanism underlying seasonal mood changes Brain scans taken at different times of year suggest that the actions of the serotonin transporter-involved in regulating the mood-altering neurotransmitter serotonin-vary by season, according to a report in the September issue of Archives of General Psychiatry, one of the JAMA/Archives journals. Different Processes Govern Sight, Light Detection A Johns Hopkins University biologist, in research with implications for people suffering from seasonal affective disorder and insomnia, has determined that the eye uses light to reset the biological clock through a mechanism separate from the ability to see. Feeling sleepy is all in your genes Genes responsible for our 24 hour body clock influence not only the timing of sleep, but also appear to be central to the actual restorative process of sleep, according to research published in the online open access journal BMC Neuroscience. Networking around the clock A Brandeis University study published in Cell this week shows for the first time experimentally that the circadian cells in fruit flies function as a network that enables the insects to adapt their behavior according to seasonal changes. Researchers figure out what makes a simple biological clock tick An interdisciplinary team of researchers at Vanderbilt University has analyzed the simplest known biological clock and figured out what makes it tick. Melatonin improves mood in winter depression Researchers at Oregon Health & Science University(OHSU) have found that melatonin, a naturally occurring brain substance, can relieve the doldrums of winter depression, also known as seasonal affective disorder, or SAD. Possible brain hormone may unlock mystery of hibernation The discovery of a possible hibernation hormone in the brain may unlock the mystery behind the dormant state, researchers reported in the April 7, 2006 issue of Cell. More Seasonal Affective Disorder Current Events and Seasonal Affective Disorder News Articles |
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