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PET scans help identify mechanism underlying seasonal mood changes
September 02, 2008Brain 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. These fluctuations may potentially explain seasonal affective disorder and related mood changes.
"It is a common experience in temperate zones that individuals feel happier and more energetic on bright and sunny days and many experience a decline in mood and energy during the dark winter season," the authors write as background information in the article. This is thought to be related to variations in brain levels of serotonin, which is involved in the regulation of functions such as mating, feeding, energy balance and sleep. The serotonin transporter, a protein that binds to serotonin and clears it from the spaces between brain cells, "is a key element in regulating intensity and spread of the serotonin signal."
Nicole Praschak-Rieder, M.D., and Matthaeus Willeit, M.D., of the Centre for Addiction and Mental Health and the University of Toronto, Ontario, Canada, and colleagues studied 88 healthy individuals (average age 33) between 1999 and 2003. Participants underwent one positron emission tomography (PET) scan to assess serotonin transporter binding potential value, an index of serotonin transporter density. The higher the binding potential value, the less serotonin circulates in the brain. For the analysis, individual scans were grouped according to the season of the scan-fall and winter or spring and summer.
"Serotonin transporter binding potential values were significantly higher in all investigated brain regions in individuals investigated in the fall and winter compared with those investigated in the spring and summer," the authors write. When they matched binding potential values to meteorological data, the researchers found that higher values occurred during times when there were fewer hours of sunlight per day.
"An implication of greater serotonin transporter binding in winter is that this may facilitate extracellular serotonin loss during winter, leading to lower mood," the authors write. "Higher regional serotonin transporter binding potential values in fall and winter may explain hyposerotonergic [related to low serotonin levels] symptoms, such as lack of energy, fatigue, overeating and increased duration of sleep during the dark season."
"These findings have important implications for understanding seasonal mood change in healthy individuals, vulnerability to seasonal affective disorder and the relationship of light exposure to mood," they conclude. "This offers a possible explanation for the regular reoccurrence of depressive episodes in fall and winter in some vulnerable individuals."
JAMA and Archives Journals
"Serotonin transporter binding potential values were significantly higher in all investigated brain regions in individuals investigated in the fall and winter compared with those investigated in the spring and summer," the authors write. When they matched binding potential values to meteorological data, the researchers found that higher values occurred during times when there were fewer hours of sunlight per day.
"An implication of greater serotonin transporter binding in winter is that this may facilitate extracellular serotonin loss during winter, leading to lower mood," the authors write. "Higher regional serotonin transporter binding potential values in fall and winter may explain hyposerotonergic [related to low serotonin levels] symptoms, such as lack of energy, fatigue, overeating and increased duration of sleep during the dark season."
"These findings have important implications for understanding seasonal mood change in healthy individuals, vulnerability to seasonal affective disorder and the relationship of light exposure to mood," they conclude. "This offers a possible explanation for the regular reoccurrence of depressive episodes in fall and winter in some vulnerable individuals."
JAMA and Archives Journals
Serotonin Current Events and Serotonin News RSSGenes determine whether sugar pills work
It is a well-known fact in drug trials that individuals can respond just as well to placebos, sugar pills, as to the active drug.
Study identifies 3 effective treatments for childhood anxiety disorders
Treatment that combines a certain type of psychotherapy with an antidepressant medication is most likely to help children with anxiety disorders, but each of the treatments alone is also effective, according to a new study funded by the National Institutes of Health's National Institute of Mental Health (NIMH).
In mice, anxiety is linked to immune system
In the first study ever to genetically link the immune system to normal behavior, scientists at Rockefeller and Columbia universities show that mast cells, known as the pharmacologic bombshells of the immune system, directly influence how mice respond to stressful situations.
New promising obesity drug may have huge potential
According to trials, a new obesity drug, Tesofensine, which may be launched on the world market in a few years, can produce weight loss twice that of currently approved obesity drugs.
Millisecond brain signals predict response to fast-acting antidepressant
Images of the brain's fastest signals reveal an electromagnetic marker that predicts a patient's response to a fast-acting antidepressant, researchers have discovered.
Genes influence effectiveness of weight-loss drug
Obese patients with a specific genetic make-up lose more weight when taking the weight loss drug sibutramine and undergoing behavioral therapy compared to those without this genetic make-up, reports a new study in Gastroenterology, the official journal of the American Gastroenterological Association (AGA) Institute.
First generation antipsychotic drugs as effective as newer ones in some children
Nearly every child who receives an antipsychotic medicine is first prescribed one of the second-generation, or "atypical" drugs, such as olanzapine and risperidone. However, there has never been evidence that these drugs are more effective than the older, first-generation medications.
Fluctuations in serotonin transport may explain winter blues
Why do many Canadians get the winter blues? In the first study of its kind in the living human brain, Dr. Jeffrey Meyer and colleagues at the Centre for Addiction and Mental Health (CAMH) have discovered greater levels of serotonin transporter in the brain in winter than in summer.
The first autism disease genes
The autistic disorder was first described, more than sixty years ago, by Dr. Leo Kanner of the Johns Hopkins Hospital (USA), who created the new label 'early infantile autism'.
Post-marketing studies finding adverse events in drugs used in children
The Food and Drug Administration Modernization Act (FDAMA, 1997), designed to stimulate more drug safety studies in children, has resulted in more than 130 label changes since its inception nearly six years ago, according to researchers at Duke Children's Hospital.
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