Seasonal influences on admissions for mood disorders and schizophrenia in a teaching psychiatric hospital in Egypt.

BACKGROUND: Distinct seasonal variation in hospital admission and various associations with the climatic parameters for mood disorders and schizophrenia have been previously reported in several world regions. There are, however, no North-African studies on this association.
METHODS: The charts of 1987 patients with mood disorders (mania 1181, depression 806) and 1359 patients with schizophrenia admitted from 2003 to 2007 from an university hospital at Mansoura, Egypt, were reviewed. Seasonality was assessed with Cosinor Analysis. Correlations of the rate of admissions for affective disorders and schizophrenia to climatic variables were performed, including lagged and differenced data.
RESULTS: There was a significant seasonal variation in the monthly admission frequencies both for mania (peak in June) and for depression (peak in December) but no significant seasonal variation was found in admissions with diagnosis of schizophrenia. The number of admissions for mania was positively correlated to indicators of temperature and luminosity, but inversely correlated to relative humidity. Quite the opposite, the number of admissions for depression showed a negative correlation to temperature and luminosity, but a positive correlation to relative humidity. 55-57% of the monthly variance of the number of admissions for mood disorders was explained by climatic variables.
CONCLUSIONS: Seasonality of admissions for mood disorders, but not for schizophrenia, has been demonstrated, in an African Mediterranean region with a fairly constant climate. The association between admission rates and climatic variables found in this study could pave the way for further studies aiming at exploration of the biological mechanism of this association as well as tailoring of treatment interventions on mood disorders.