PET scans help identify mechanism underlying seasonal mood changes

Sep 02, 2008

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. 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."

Source: JAMA and Archives Journals

Explore further: Scientists discover new clues to how weight loss is regulated

add to favorites email to friend print save as pdf

Related Stories

Report: Better shields needed for private tax data

14 minutes ago

Federal investigators say the IRS and the states should improve how they protect the security of confidential tax information of people getting benefits under the 2010 health care law.

Coal-rich Poland ready to block EU climate deal

17 minutes ago

European Union leaders meeting in Brussels to set their new greenhouse gas emissions plan are facing staunch opposition from coal-reliant Poland and other East European countries who say their economies would ...

Some online shoppers pay more than others, study shows

42 minutes ago

Internet users regularly receive all kinds of personalized content, from Google search results to product recommendations on Amazon. This is thanks to the complex algorithms that produce results based on users' profiles and ...

Researchers create designer 'barrel' proteins

44 minutes ago

Proteins are long linear molecules that fold up to form well-defined 3D shapes. These 3D molecular architectures are essential for biological functions such as the elasticity of skin, the digestion of food, ...

Recommended for you

Growing a blood vessel in a week

1 hour ago

The technology for creating new tissues from stem cells has taken a giant leap forward. Three tablespoons of blood are all that is needed to grow a brand new blood vessel in just seven days. This is shown ...

Testing time for stem cells

4 hours ago

DefiniGEN is one of the first commercial opportunities to arise from Cambridge's expertise in stem cell research. Here, we look at some of the fundamental research that enables it to supply liver and pancreatic ...

Team finds key signaling pathway in cause of preeclampsia

23 hours ago

A team of researchers led by a Wayne State University School of Medicine associate professor of obstetrics and gynecology has published findings that provide novel insight into the cause of preeclampsia, the leading cause ...

Rapid test to diagnose severe sepsis

Oct 23, 2014

A new test, developed by University of British Columbia researchers, could help physicians predict within an hour if a patient will develop severe sepsis so they can begin treatment immediately.

User comments : 0