Factors associated with age of onset of illness among patients with schizophrenia: A cross-sectional study from South India

AIM/OBJECTIVES: The aim of the study was to estimate the age of onset of illness and to examine the various socio-demographic, biological and clinical variables associated with the age of onset of illness among patients with schizophrenia from the South Indian State of Tamil Nadu. MATERIALS AND METHODS: This is a cross-sectional study with data collected from different rural and urban settings in Tamil Nadu, including 947 patients diagnosed with schizophrenia according to DSM IV TR. The age of onset of schizophrenia obtained via patient and informant history, was studied in relation to socio-demographic, biological and clinical variable including gender, family history, consanguinity, birth order, parental age and severity of symptoms collected using semi-structured interview, SANS and SAPS. RESULTS: The study showed a mean age of onset of 25years (SD = 8) in our population. Univariate analysis showed significant relation between age of onset and gender with a preponderance of early onset in men(p=0.017). The results showed no significant association with the other variable under study. The age of onset was seen to have significant negative correlation with the severity of illness (r=-0.75, p=0.021). DISCUSSION AND CONCLUSION: The male preponderance for early onset of schizophrenia, has been supported by prior literary evidences indicating various genetic, social and hormonal underpinnings. However the absence of association between age of onset and family history, consanguinity and its degrees, which are strong genetic determinants, alludes to the influence of other environmental factors on onset of schizophrenia. Despite the known influence of parental age in de novo mutations leading to increased risk of schizophrenia, no observed association with parental age and birth order, only reinforces the need to further explore other direct influencers on the age of onset, as the negative correlation between age of onset and symptom severity seen in the study, suggests that prolonging the age of onset may in-turn have desirable effect on disease outcome.