2017 Volume 8 Pages 7-11
Purpose: Recently, we reported that lithium levels in drinking water were significantly and positively associated with hyperthymic temperament scores, whereas latitude was significantly and negatively associated with the scores, suggesting that lithium in drinking water may positively maintain hyperthymic temperament and that latitude may negatively maintain it. In the present study, from the viewpoint of psychopharmacology, we investigated the other 4 affective temperaments in reference to lithium in drinking water with adjustment for latitude, temperature, and sunshine. Methods: We re-examined our previous dataset consisting of temperament data of 609 residents in Sapporo, Obihiro, Takaoka, Koshigaya, and Oita cities, in addition to the lithium levels in drinking water and climatic data of the five cities. Multiple regression analyses via the forced entry method were performed, whereby the individual temperament scores were dependent factors, and age, gender, the other four affective temperaments, lithium in drinking water, latitude, temperature, and sunshine were independent factors. Results: The multiple regression analysis revealed that lithium levels in drinking water were significantly and negatively associated with depressive temperament scores. The other three temperaments (i.e. irritable, cyclothymic and anxious temperaments) were not significantly associated with lithium levels in drinking water. Discussion: In conclusion, the present findings suggest that lithium in drinking water may be negatively associated with depressive temperament.