Dose-dependent effects of light on hyperthymic temperament.
BACKGROUND
In a previous study examining the association of hyperthymic temperament and daily light exposure (illuminance), we compared hyperthymic scores of the Temperament Evaluation of Memphis, Pisa, Paris and San Diego-auto questionnaire version (TEMPS-A) acquired from residents in Sapporo and Oita in Japan, which are located at 43° and 33° of latitude. We found that residents of Oita had significantly higher hyperthymic scores than residents of Sapporo. Moreover, a comparison of 3 regions rather than 2 regions may show a dose-response relationship in hyperthymic temperament and illuminance.


METHODS
Japan has 4 large islands-Hokkaido, Honshu, Shikoku, and Kyushu. Sapporo is in Hokkaido and Oita is in Kyushu. As the 3rd location, we recently collected TEMPS-A data from 125 residents in Koshigaya which is located in Honshu at 36°. We combined the data of the Koshigaya residents with the data of 94 residents from Sapporo and 95 from Oita.


RESULTS
The mean yearly total sunshine of the past 20 years (1993-2012) was 1684.6h in Sapporo, 1862.9h in Koshigaya, and 2002.9h in Oita. Multiple regression analyses revealed that sunshine predicted significant variance of hyperthymic temperament in a dose-dependent manner.


CONCLUSIONS
The limitation of the present study is the lack of the consideration of the effects of temperature on hyperthymic temperament. Since correlations are fairly small, other factors are also at work for hyperthymic temperament.


CONCLUSIONS
The present findings suggest that higher illuminance may maintain hyperthymic temperament via light effects in a dose-dependent manner.
Department of Neuropsychiatry, Oita University Faculty of Medicine, Oita 879-5593, Japan.
Kentaro
K
Kohno
Department of Psychiatry, Juntendo University School of Medicine, Chiba, Japan; Department of Psychiatry, Juntendo Koshigaya Hospital, Koshigaya, Japan.
Hajime
H
Baba
Department of Psychiatry, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
Takeshi
T
Inoue
Department of Psychiatry, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
Yukiei
Y
Nakai
Department of Psychiatry, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
Atsuhito
A
Toyomaki
Department of Psychiatry, Juntendo University School of Medicine, Chiba, Japan; Department of Psychiatry, Juntendo Koshigaya Hospital, Koshigaya, Japan.
Toshihito
T
Suzuki
Department of Neuropsychiatry, Oita University Faculty of Medicine, Oita 879-5593, Japan.
Koji
K
Hatano
Department of Psychiatry, Juntendo University School of Medicine, Chiba, Japan; Department of Psychiatry, Juntendo Koshigaya Hospital, Koshigaya, Japan.
Heii
H
Arai
Department of Neuropsychiatry, Oita University Faculty of Medicine, Oita 879-5593, Japan. Electronic address: terao@oita-u.ac.jp.
Takeshi
T
Terao
D000328:Adult; D001714:Bipolar Disorder / Q000523:psychology*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D007564:Japan; D008297:Male; D012044:Regression Analysis; D015203:Reproducibility of Results; D013472:Sunlight; D011795:Surveys and Questionnaires; D013694:Temperament / Q000528:radiation effects*; D055815:Young Adult
Hyperthymic temperament; Light; Sunshine; TEMPS-A