Chronobiology deals with the study of biological rhythms, the most significant of which is the circadian rhythm, which is approximately of 24 hour duration, and which regulates or affects many physiological functions. A disruption of endogenous circadian rhythms caused by seasonal variations in the duration and intensity of natural daylight was first described by the psychiatrist Norman Rosenthal and colleagues in 1984. They coined the expression Seasonal Affective Disorder (SAD) to include the disturbances, especially of mood, experienced by sufferers. Thirty years after that initial publication a Witness Seminar was held, at which psychiatrists, chronobiologists, endocrinologists and SAD sufferers discussed the definition, impact and acceptance of SAD as a diagnostic entity; the longer history of seasonal variation in mood, and relevant clinical and scientific work. Of particular note was the work of Professor Josephine Arendt, and her studies of light therapy and melatonin to “re-set” disturbed circadian rhythms.
A biochemist by training, Professor Josephine Arendt pioneered the field of chronobiology, developing the first sensitive technique for measuring melatonin through radioimmunoassay. She discusses the lengths she went to in pursuit of evidence about the mechanisms governing sleep-wake cycles, even using herself as a guinea pig for studying sleep disorders.