Manic depressive illness: onset, diurnal temperature and season of birth.

Fifty-six carefully diagnosed manic-depressive patients were evaluated seeking a relationship between onset of the illness, diurnal temperature variation, and month and season of birth. With respect to diurnal temperature variation, we were able to discover no significant change in the difference between the high and low temperature as the time of onset of each episode of the illness approached, but there was a trend for the high-low temperature difference to decrease as time of onset approached. Occurrence of episodes was seasonally distributed with significantly more hospitalizations in winter and spring and fewer in summer and fall. The cohort of manic-depressive patients was not different from the Indiana population generally with respect to season of birth.