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Seasonality of mania: a Tasmanian study
Objective:
The aim of the study was to examine the seasonal incidence of mania in a new Southern Hemisphere location.
Method:
Using the Tasmanian psychiatric database, monthly admission rates were compared with expected admission rates for mania for the period 1983 to 1989. ICD-9 criteria for mania single episode (296.0) and mania recurrent episodes (296.1) were used, excluding individuals with a bipolar disorder (296.4 to 296.89).
Results:
One thousand three hundred and twenty-eight persons were admitted during this period. There was a significant monthly variation with admissions occurring most commonly in the summer, but this was not consistent during the seven year period.
Conclusions:
There was a statistically significant but inconstant summer excess. The inconstancy of the finding suggests that the phenomenon is not a simple consequence of light duration, and closer examination of these inconsistencies may lead to further elucidation of the phenomenon.
Insights
Mania admissions show a seasonal pattern, peaking in summer in Tasmania, but this trend was inconsistent over seven years. Further research is needed to understand the underlying causes of this phenomenon.
Area of Science:
- Psychiatry
- Chronobiology
- Epidemiology
Background:
- Seasonal variations in mental health conditions are increasingly recognized.
- Understanding geographical differences in these patterns is crucial for public health.
Purpose of the Study:
- To investigate the seasonal incidence of mania in Tasmania, a Southern Hemisphere location.
- To analyze monthly admission rates for mania between 1983 and 1989.
Main Methods:
- Utilized the Tasmanian psychiatric database for admissions data.
- Applied International Classification of Diseases, 9th Revision (ICD-9) criteria for mania (296.0, 296.1).
- Excluded individuals diagnosed with bipolar disorder (ICD-9 codes 296.4–296.89).
Main Results:
- A total of 1,328 individuals were admitted for mania during the study period.
- A statistically significant variation in monthly admissions was observed.
- Mania admissions were most frequent during the summer months, though this pattern lacked consistency throughout the seven years.
Conclusions:
- A statistically significant, yet inconsistent, excess of mania admissions occurred during summer.
- The inconsistency suggests that light duration alone may not explain the seasonal pattern.
- Further investigation into these inconsistencies could provide deeper insights into the etiology of mania seasonality.