Admission rates of bipolar depressed patients increase during spring/summer and correlate with maximal environmental temperature

Avraham Shapira, Roni Shiloh, Oded Potchter, Haggai Hermesh, Miriam Popper, Abraham Weizman

Research output: Contribution to journalArticlepeer-review


Objective: We intended to identify a relationship, if exists, between various climatic factors and the admission rates of bipolar affective disorder depressed patients (BPD) or major depressive disorder patients (unipolar) (UPD) to psychiatric hospitals, as well as potential seasonal variability in hospitalization rates of this population. Methods: Data on admissions of ICD-9 BPD and UPD patients to Tel Aviv's seven public psychiatric hospitals during 11 consecutive years were collected along with concomitant meteorological information. Results: Admissions of 4117 patients with BPD and 1036 with UPD who fulfilled our specific inclusion criteria were recorded. Bipolar depressed, but not UPD, patients exhibited significant seasonal variation (higher spring and summer versus winter mean monthly admission rates), and the admission rates of patients with BPD, but not UPD, correlated significantly with mean maximal monthly environmental temperature Conclusions: Increased environmental temperature may be a risk factor for evolvement of major depressive episode in patients with bipolar disorder with psychiatric co-morbidity, at least in cases that necessitate hospitalization and at the examined geographic/climatic region of Israel. Further large-scale studies with bipolar depressed patients with and without co-morbid disorders are needed to substantiate our findings and to determine the role of seasonal and climatic influence on this population, as well as its relationship to the pathophysiology of bipolar disorder.

Original languageEnglish
Pages (from-to)90-93
Number of pages4
JournalBipolar Disorders
Issue number1
StatePublished - Feb 2004
Externally publishedYes


  • Bipolar affective disorder
  • Climate
  • Depression
  • Environmental temperature
  • Major depressive disorder (unipolar)
  • Seasonality


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