Seasonality of three dimensions of mania: Psychosis, aggression and suicidality

Abstract

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.

Introduction

Seasonality of mania has been reported all over the globe. In Brazil, a seasonal distribution of admissions for mania was described, with a clear late winter/early spring peak, which correlated positively with luminosity and with rapidly increasing temperatures, and negatively with rainfall and humidity (Volpe and Del Porto, 2006). Vulnerability to seasonal changes seems to be a separate dimension of bipolar disorder, partially determined by genetics (Madden et al., 1996). Which, and how, specific symptoms are susceptible to climatic influences is so far an unresolved matter that would further clarify how seasons affect the course and prognosis of bipolar disorder.

The fact that manic episodes are not uniform and their clinical presentation varies on the diverse dimensions of bipolarity has been pointed out since Kraepelin and confirmed by others (Sato et al., 2003, Cassidy et al., 2002). Psychosis (Swann et al., 2004), aggression (Volpe and Tavares, 2003, Volpe et al., 2003) and suicidality (Schou, 1999) are important aspects of mania, which indicate severity (Carlson and Goodwin, 1973) and which differentially direct treatment options and influence outcomes.

Studies of psychiatric and community samples provide robust evidence that the occurrence of psychosis (Shiloh et al., 2005, Davies et al., 2000, Clarke et al., 1999), aggression (Kaplan et al., 1996, Roitman et al., 1990), and suicide (Lee et al., 2006, Deisenhammer et al., 2003, Preti, 1997) varies along the course of the year, influenced by climatic conditions. The main hypotheses underlying these findings imply biological mechanisms on the climatic influences into mood and behavior, melatonergic and serotonergic dysfunctions being the stronger claims.

This study investigates the existence of a seasonal distribution of these three dimensions of mania in a Brazilian sample, during psychiatric admissions, correlating these findings with local climatic variables.