Introduction: Some controversy exists concerning whether the onset of schizophrenia and some clinical characteristics of the disorder are different between males and females.
Objective: The relationship between sex, age at onset and negative symptoms was evaluated in patients with schizophrenic spectrum disorders.
Materials and methods: A sample of 225 patients (89 women and 136 men) were diagnosed for schizophrenia between 2008 and 2009. Each was compared for age at onset of symptoms and SANS score (Scale for the Assessment of Negative Symptoms). Kernel density estimators were used to evaluate characteristics of age of onset with respect to gender. Parameters of the mixed distributions were estimated via maximum-likelihood algorithms. Relationships between negative symptoms score and age of onset were evaluated using multiple regression analysis.
Results: A significant difference was found in age at onset across gender (mean age of 24.5 years in men, 27.5 years in women). An association was found between gender and early onset of symptoms, with early onset occurring more frequently in male patients. Density estimates for age at onset suggested a mixture model with three components having as parameters: m1=21.55 +/- SD 5.25; m2=29.54 +/- SD 7.22; m3=40.01 +/- 3.98. When density estimates took into account gender, two bimodal structures were found--(1) men with the lowest mean (18.0 years) and (2) the highest mean in middle-aged women (41.0 years). Regression coefficients suggested an increase in negative symptoms as time of disease increased.
Conclusion: The hypothesis was supported that a relationship exists between age of onset of symptoms, gender and clinical characteristics in patients with schizophrenic spectrum disorders, showing that men have an early onset an a more deteriorating course than women.