Brain's Serotonin May Explain Seasonal Mood Changes

Higher binding potential in winter could clarify why people
feel down when sun shines less

(HealthDay News) -- Fluctuations in the actions of the
serotonin transporter, which helps regulate the mood-altering
neurotransmitter serotonin, may help explain seasonal affective
disorder and related mood changes, researchers say.

In places where the weather changes with the seasons, people
commonly feel happier and more energetic when the days are
bright and sunny and more depressed and fatigued during the dark
of winter. Scientists believe this is related to variations in
brain levels of serotonin, a neurotransmitter involved in
regulating functions such as mating, feeding, energy balance,
and sleep.

In a study published in the September issue of the Archives of
General Psychiatry, researchers from the Centre for Addiction
and Mental Health and the University of Toronto had 88 healthy
people undergo a positron emission tomography (PET) scan to
assess serotonin binding potential, which indicates serotonin
transporter density. The higher the serotonin binding potential,
the less serotonin that is circulating in the brain.

To study seasonal fluctuations of serotonin binding potential,
the researchers grouped the PET scans according to the season of
the scan -- fall and winter or spring and summer.

The serotonin binding potentials were significantly higher
during the fall and winter months than in the spring and summer,
indicating that less serotonin circulates in the brain during
the darker, colder time of the year. The researchers compared
their findings to meterological data and found higher values of
serotonin binding potentials during times when there were fewer
hours of sunlight each day.

The researchers said that higher serotonin binding potential in
the winter may help explain why people report lower mood, lack
of energy, fatigue, overeating, and increased sleeping during
the darker seasons.

"This offers a possible explanation for the regular
reoccurrence of depressive episodes in fall and winter in some
vulnerable individuals," the researchers wrote.

Ask Dr. Tang how we can balance and stabilize your serotonin levels without resorting to costly and potentially fatal anti-depressants.