The environment and the internal clocks: The study of their relationships from prehistoric to modern times.

The origin of biological rhythms goes back to the very beginning of life. They are observed in the animal and plant world at all levels of organization, from cells to ecosystems. As early as the 18th century, plant scientists were the first to explain the relationship between flowering cycles and environmental cycles, emphasizing the importance of daily light-dark cycles and the seasons. Our temporal structure is controlled by external and internal rhythmic signals. Light is the main synchronizer of the circadian system, as daily exposure to light entrains our clock over 24 hours, the endogenous period of the circadian system being close to, but not exactly, 24 hours. In 1960, a seminal scientific meeting, the Cold Spring Harbor Symposium on Biological Rhythms, brought together all the biological rhythms scientists of the time, a number of whom are considered the founders of modern chronobiology. All aspects of biological rhythms were addressed, from the properties of circadian rhythms to their practical and ecological aspects. Birth of chronobiology dates from this period, with the definition of its vocabulary and specificities in metabolism, photoperiodism, animal physiology, etc. At around the same time, and right up to the present day, research has focused on melatonin, the circadian neurohormone of the pineal gland, with data on its pattern, metabolism, control by light and clinical applications. However, light has a double face, as it has positive effects as a circadian clock entraining agent, but also deleterious effects, as it can lead to chronodisruption when exposed chronically at night, which can increase the risk of cancer and other diseases. Finally, research over the past few decades has unraveled the anatomical location of circadian clocks and their cellular and molecular mechanisms. This recent research has in turn allowed us to explain how circadian rhythms control physiology and health.

Decreased Immune Response in Alexithymic Women: A One-Year Longitudinal Study.

Although previous cross-sectional studies suggested significantly dysregulated immune response in alexithymia, there is a lack of longitudinal studies. We sought to determine the reliability of the reported relationship between alexithymia and decreased immune response in a longitudinal study. Thirty-eight healthy women who had participated in a cross-sectional study were recontacted 1-year later. Of this sample, 26 were finally included: 13 females who had been found to be alexithymic, and 13 females who were classified as non-alexithymic under the 20-item Toronto Alexithymia Scale during the first phase of the study. A year later, they were still healthy women without any psychiatric disorders, their ages now ranging from 19 to 28 years old. Lymphocyte subset counts (CD4, CD8), in vitro production of interleukin 1ß (IL-1ß), IL-2, IL-4, and IL-10 by phytohemagglutinin stimulated peripheral blood lymphocytes, as well as serum cortisol levels, were compared between women with and without alexithymia. One-year later, alexithymic women still had significantly lowered in vitro production of IL-2 and IL-4, with lowered IL-2/IL-10 ratio and a reduced percentage of CD4. This is the first ever published study assessing cytokine production during a follow-up of alexithymics. Although our results should be interpreted with caution due the small sample size, they suggest a sustained reduction in both major type 1 and type 2 cytokines while the former seems to be more affected. The potential long-term health impact, if any, is still to be determined.

Decreased immune response in alexithymic women: a cross-sectional study.

It has been reported in a few studies that alexithymia is associated with impaired immune response but results are still contradictory. The present study investigates whether alexithymia is associated with lower cell-mediated (Th-1) immune response. Fifty-one healthy 18-27-year-old women were selected from healthy subjects on the basis of high or low cut-off scores on the 20-item Toronto Alexithymia Scale (TAS-20). They were evaluated using standardized psychiatric rating scales notably the Hospital Anxiety Depressive Scale (HAD) and the Mini Neuropsychiatric Interview (MINI). None of the subjects were suffering from psychiatric disorders. Twenty-seven were classified as alexithymics and 24 as non-alexithymics according to the TAS-20. Blood was drawn for lymphocyte subset counts (CD4, CD8), in vitro production of interleukin 1 (IL-1beta), IL-2, IL-4, and IL-10 by phytohaemagglutinin stimulated peripheral lymphocytes, and cortisol. Women with alexithymia exhibited decreased interleukin 1beta, IL-2 and IL-4 production with reduced ratios of Th1/Th2 (IL-2/IL-10) and of CD4/CD8, as well as reduced CD4 percentages. IL-2 and IL-4 production remained significantly diminished in the alexithymic group, even after adjusting for between-group differences in anxiety and depression levels on the HAD. This study further demonstrates that alexithymic women have altered immune function, with a predominance of depressed cell-mediated immunity and a skewed Th1/Th2 ratio towards Th2 response.