Seasonality and bipolar disorder: a systematic review, from admission rates to seasonality of symptoms.
Level 3 - non-randomized controlled study
Systematic review of observational epidemiological and cross-sectional studies
PubMed 25063960 · doi:10.1016/j.jad.2014.07.002
What was done
Systematic review assessing seasonality in bipolar disorder across 51 published studies. Studies were classified into seasonal admission rates (n = 32), categorical diagnoses (n = 6), and seasonal symptom dimensions (n = 13).
What was found
Across worldwide studies, manic episodes peaked in spring/summer (and secondarily in autumn), depressive episodes peaked in early winter (and secondarily in summer), and mixed episodes peaked in early spring or mid/late summer. Seasonal patterns occurred in approximately 15% of manic episodes and 25% of depressive episodes. Depressive seasonality was associated with bipolar II subtype, comorbid eating disorders, more relapses, and rapid cycling. Individuals with bipolar disorder exhibited greater seasonal fluctuations in mood and behavior compared to healthy controls and patients with unipolar depression.
Why it matters
Synthesizes global epidemiological evidence confirming seasonal patterns in bipolar relapse, supporting chronobiological approaches to timing interventions and preventive care.
Limits
The included studies varied widely in sample size, gender representation, methodological quality, and analytical sophistication. Findings rely entirely on observational and registry data, and the abstract does not report pooled quantitative effect estimates or formal risk of bias scoring.
Cited by
- context Systematic reviews of patient hospitalizations show that manic episodes peak around the spring equinox and autumn equinox.
- supports Systematic reviews show that bipolar depressive episodes peak around the winter solstice when photoperiod is at its lowest.