Background: A number of studies have established that manic patients have higher rates of hospitalization in spring. There appears to be no data evaluating whether there is any seasonal variation in hospitalization for those with hypomania.
Methods: Data were obtained for 27,255 individuals hospitalized in NSW psychiatric hospitals over a 14-year period (2000-2014) for ICD-10 diagnosed mania or hypomania. Graphical analyzes examined rates of hospitalisation for hypomania and mania separately, using monthly and seasonal averages.
Results: Admission rates were higher for mania compared to hypomania and there was a similar pattern across seasons - with admissions being at their lowest in autumn, increasing in winter, and at their highest for spring. Monthly percentage scores were similar for mania and hypomania and indicated lower admission rates in the first six months of the year (January-June), with a sudden increase in July, and followed by a more gradual increase until December.
Limitations: Hospitalization rates do not necessarily provide an accurate estimate of the onset of hypo/manic episodes, while the validity of those assigned a diagnosis of hypomania could not be established, allowing the possibility that many may have had manic episodes.
Conclusions: Findings indicate that hypomania shows a similar seasonal pattern to mania.
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