Seasonality of three dimensions of mania: psychosis, aggression and suicidality.

BACKGROUND: To investigate the existence of a seasonal distribution of three dimensions of mania, psychosis, aggression and suicidality, during psychiatric hospitalizations, in a Brazilian sample, correlating these findings with local climatic variables.
METHODS: Charts of 425 admissions of 269 ICD-10 manic patients, from 1996-2000 were reviewed for the occurrence of these symptom dimensions. Seasonality was assessed using Cosinor Analysis. When a harmonic seasonal distribution was not present, chi-square tests comparing the peak months with the rest of the year for each specific feature were performed. Correlations were performed between the three mania features and the index and previous months' predictor climatic variables (mean temperature, hours of sunshine, duration of days, relative humidity and rainfall).
RESULTS: Cosinor regressions showed non-significance. However, rates of aggression were significantly higher in January-March than in the rest of the year (62 vs. 50%; p=0.007), and suicidality was significantly more frequent in December and January (20 vs. 10%; p=0.019). Suicidality was significantly correlated to rapidly increasing temperatures (rs=0.28; p<0.05). Psychosis was positively correlated with hours of sunshine of index month and with increasing hours of sunshine (rs=0.40 and 0.35; p<0.01); but negatively correlated with relative humidity of index month and with difference from previous to index month (rs=-0.25 and -0.30; p<0.05). Climatic variables studied were not significantly correlated with aggression. LIMITATIONS: Retrospective study on a single institution.
CONCLUSION: Climatic conditions correlated differently with each dimension of mania.