Less available supplies of serotonin during winter months
According to recent findings published in the September issue of Archives of General Psychiatry, serotonin transporter binding potential is higher during the winter solstice creating less available supplies of serotonin. Specifically, serotonin transporter binding potential, as measure in vivo with positron emission tomography, were higher in various brain regions of healthy volunteers by 10.6% to 16.1% close to the winter solstice. Jeffrey H. Meyer, M.D., Ph.D., of the Center for Addiction and Mental Health, and colleagues, commenting wrote, “given that the serotonin transporter has a role in clearing extracellular serotonin, 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.” The following is an excerpt of an article from Medpage Today that discusses the study’s findings:
“Higher regional serotonin transporter binding potential values in fall and winter may explain hyposerotonergic symptoms, such as lack of energy, fatigue, overeating, and increased duration of sleep during the dark season.”
Dr. Meyer and colleagues suggested that full-blown depression may result when these normal seasonal variations combine with other factors, such as increased intracellular serotonin degradation.
“This offers a possible explanation for the regular reoccurrence of depressive episodes in fall and winter in some vulnerable individuals,” they said.
The largest seasonal difference was in the mesencephalon, while the putamen and thalamus had the smallest variations.
Peak-to-trough differences were substantially greater than the averages of spring-summer versus fall-winter. They reached 41.5% in the mesencephalon, while in the putamen there was only a 22.1% from the highest to the lowest month.
Dr. Meyer and colleagues found significant (P≤0.05) negative correlations between serotonin transporter binding potential and day length, with Spearman coefficients ranging from -0.20 (anteromedial prefrontal cortex) to -0.38 (mesencephalon).