FED/ Researchers uncover possible cause of seasonal disorder

07 декабря, 2002
Judy Skatssoon, National Medical Writer 12/06/2002 SYDNEY, Dec 6 AAP - Melbourne researchers have found the first strong evidence of a possible cause for seasonal mood disorder, where people regularly become depressed during winter but recover in summer. AAP News via NewsEdge Corporation : Judy Skatssoon, National Medical Writer 12/06/2002 SYDNEY, Dec 6 AAP - Melbourne researchers have found the first strong evidence of a possible cause for seasonal mood disorder, where people regularly become depressed during winter but recover in summer. According to a research letter in The Lancet medical journal today, a lack of sunlight inhibits production of the "feel-good"neurotransmitter serotonin. Seasonal mood disorder was first documented in the mid 1980s but Hippocrates alluded to it as far back as 400BC. Dr Gavin Lambert, of Melbourne's Baker Institute, concluded lack of light affects key mood-controlling neurotransmitters in the brain. He said he measured levels of brain serotonin and other neurotransmitters by inserting a catheter high into internal jugular veins to obtain blood samples. Analysis of the samples showed that serotonin levels were much lower in winter than in spring and summer, and this was directly related to the amount of bright sunlight. "Up until this stage there's really only been indirect evidence that brain serotonin may be involved in this disease, or that other neurotransmitters may be involved," Dr Lambert told AAP. "What our research has done is provide strong evidence of a link between a seasonal variation in brain serotonin and a strong link between the amount of sunlight and brain serotonin." Previous postmortem studies also found serotonin levels lower in the brains of suicide victims. Meanwhile, shining a bright light into rats eyes had been shown to activate neurones in the hypothalamus, one of the mood-controlling centres of the brain. Seasonal mood disorder, which can be severe enough to put people at risk of suicide, is believed to have a genetic element, however it becomes more prevalent with increasing distance from the equator. Light therapy, or shining bright white light into a patients' eyes, has been shown to be effective in treating the disorder. But summer also posed a mental health hazard for certain people, Dr Lambert said. According to separate research, to be published next year, more people kill themselves in summer and spring than in winter. Dr Lambert admitted the figures posed a conundrum given the earlier study. "You could speculate that the rate of change from low level serotonin that occurred between winter and summer could result in an acute activation of serotonergic neurones in the brain, causing pronounced anxiety in susceptible individuals," he said. It could also account for people with bipolar depression having pronounced symptoms in spring and summer, Dr Lambert said. AAP jjs/csd/de Copyright 2002. All Rights Reserved. Financial Times Information Limited - Asia Africa Intelligence Wire <> << Copyright ©2002 Financial Times Limited, All Rights Reserved >>
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