BACKGROUND Increasing evidence from clinical practice, as well as from epidemiological and basic research shows that there are gender differences in clinical features of schizophrenia, and this may be related to estrogens. There may be a relationship between earlier puberty and later onset of the disease, because of the protective effects of estrogens in women with schizophrenia. In this study, our aim was to analyze the correlation between age of menarche and age of onset of schizophrenia and to investigate the protective effects of estrogens in schizophrenia. METHODS In this study, we included 289 patients who were diagnosed with schizophrenia. Those with mental deficiency or organic brain disorders were excluded from the study. All subjects were given a socio-demographic form to determine their personal information, age at menarche, age at first odd behavior, age at onset of the disease and first hospitalization. Data on factors which may affect the association between age at onset of schizophrenia and age at menarche such as family history, head or birth trauma etc. were recorded on the information form. RESULTS We found out that age at menarche was negatively associated with age at first odd behavior and age at first psychotic symptoms. CONCLUSIONS Our study verifies the protective effects of estrogens and shows that the earlier puberty may be the cause of later onset of schizophrenia. A gender-sensitive approach in psychiatry improves our understanding of mental illness and our therapeutic strategies.