Relationship among latitude, climate, season and self-reported mood in bipolar disorder.
OBJECTIVE
Many researchers have analyzed seasonal variation in hospital admissions for bipolar disorder with inconsistent results. We investigated if a seasonal pattern was present in daily self-reported daily mood ratings from patients living in five climate zones in the northern and southern hemispheres. We also investigated the influence of latitude and seasonal climate variables on mood.


METHODS
360 patients who were receiving treatment as usual recorded mood daily (59,422 total days of data). Both the percentage of days depressed and hypomanic/manic, and the episodes of depression and mania were determined. The observations were provided by patients from different geographic locations in North and South America, Europe and Australia. These data were analyzed for seasonality by climate zone using both a sinusoidal regression and the Gini index. Additionally, the influence of latitude and climate variables on mood was estimated using generalized linear models for each season and month.


RESULTS
No seasonality was found in any climate zone by either method. In spite of vastly different weather, neither latitude nor climate variables were associated with mood by season or month.


CONCLUSIONS
Daily self-reported mood ratings of most patients with bipolar disorder did not show a seasonal pattern. Neither climate nor latitude has a primary influence on the daily mood changes of most patients receiving medication for bipolar disorder.
Bauer
Michael
M
Department of Psychiatry and Psychotherapy, Universitätsklinikum Carl Gustav Carus, Technische Universität Dresden, Germany Fetscherstr. 74, 01307 Dresden, Germany. Michael.Bauer@uniklinikum-dresden.de
Glenn
Tasha
T
Grof
Paul
P
Rasgon
Natalie L
NL
Marsh
Wendy
W
Sagduyu
Kemal
K
Alda
Martin
M
Murray
Greg
G
Quiroz
Danilo
D
Malliaris
Yanni
Y
Sasse
Johanna
J
Pilhatsch
Maximilian
M
Whybrow
Peter C
PC
D000328:Adult; D000339:Affect; D001315:Australia / Q000453:epidemiology; D001714:Bipolar Disorder / Q000453:epidemiology / Q000523:psychology*; D002980:Climate; D003863:Depression / Q000453:epidemiology / Q000523:psychology*; D005060:Europe / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D009656:North America / Q000453:epidemiology; D011569:Psychiatric Status Rating Scales; D012621:Seasons; D012720:Severity of Illness Index; D013020:South America / Q000453:epidemiology; D013997:Time Factors