We thank Drs Chandra and Babu for their comments, but we would like to emphasise that we had never recommended the addition of lithium to drinking water supplies Reference Ohgami, Terao, Shiotsuki, Ishii and Iwata1 because our findings are preliminary and yet to be conclusive.
First, we agree that sociological factors such as migration, poverty, human relations and economic issues may be associated with suicide rates, and have already admitted such limitations by stating ‘other factors such as psychosocial and economic factors were not taken into consideration’. Reference Ohgami, Terao, Shiotsuki, Ishii and Iwata1 Second, Drs Chandra and Babu state that it is also important to assess side-effects of lithium in tap water on thyroid function, pregnant women and the unborn fetus. Although it seems probable that these low levels of lithium are far below the levels required to produce side-effects, we agree with them. Third, they mention lithium levels in food, also raised by Drs Desai and Chaturvedi. This may be important because dietary lithium intake is estimated not to be a negligible quantity. For example, mean (s.d.) dietary lithium was reported to be: 1560 μg/day (980) in China; 1485 (1009) (Tijuana) and 939 (928) (Culiacan) in Mexico; 1090 (324) in Sweden; 1009 (324) in Denmark; 821 (684) (Texas), 650 (740) (New York) and 429 (116) (San Diego) in the USA; 812 (383) in Japan; 406 (383) in Germany; and 348 (290) in Austria. Reference Schrauzer2 Therefore, at the next stage, it would seem necessary to measure serum lithium levels in participants, incorporating total lithium intake of both drinking water and food.