A Neurophysiological Study of Seasonal Affective Disorder-with Special Reference to Changes in the Plasma Level of Tryptophan-

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The author treated 10 patients with seasonal affective disorder (SAD) in the study period 3 years.Although it was in an extremely limited number of SAD patients that phototherapy could be applied in complete compliance with the conditions of the study program, the following notable characteristics of SAD were extracted from them in this study.(1) Characteristics of Biological Traits of SAD and Effects of Phototherapy1) The plasma level of free tryptophan was significantly depressed in the SAD patients,to about 5% of the average value for healthy persons. When the patients were instituted on phototherapy, there was a significant increase of 10% in the plasma level of free tryptophan with the improvement of clinical symptoms.2) The diurnal rhythm of melatonin was not remarkable, but its secretion tended to decrease.3) Cortisol secretion tended to increase all the time, and the reverse was the case with prolactin secretion. With phototherapy, the phase of secretion of melatonin, prolactin,and cortisol was advanced 2 to 3 hours.4) The body temperature rhythm was also advanced about 4 hours, but it cannot necessarily be argued that this effect represents the core of the mechanism of phototherapy.(2) Effects of Phototherapy on the Sexual GlandIt is said that SAD is characteristically common in women, especially those who present with premenstrual tension syndrome. It was suggested that light irradiation, which fails to receive much attention in Japan, was inhibitive of ovulation and luteal function.(3) Relationship of SAD to HeredityWhen this series of SAD patients was examined for familial onset, 3 pairs of a parent and a child were found among the 10 SAD patients. This finding suggests such a strong predisposition to SAD that further studies are warranted in this respect.