ABSTRACT 
 Objectives: 1.To determines impact of familial risk factor i.e. positive family history of schizophrenia on age of onset of schizophrenia.
 2. To determine impact of environmental risk factor i.e. substance misuse on age of onset of schizophrenia.
 Materials and Methods: In this cross sectional analytical study, 430 patients were enrolled from OPD in Sarhad Hospital for Psychiatric Diseases Peshawar through convenience non probability sampling technique. First Data was dichotomized on the basis of positive and negative family history of schizophrenia. Later on data was again dichotomized on the basis of positive and negative history of substance misuse. Frequency and percentage were calculated for categorical variable while mean and standard deviation for continuous variables. Independent-samples T test was used while comparing categorical variable with continuous variable and Chi-square test was used while comparing two categorical variables in between them.
 Results: The mean age of onset of schizophrenia was 22.28 years with early onset in males than females. In those with familial schizophrenia, the mean ages of onset of schizophrenia in males and females were 22.35 and 22.05 years while in those with sporadic cases, the mean age of onset of schizophrenia in males and females were 21.83 and 25.43 years respectively. Moreover non-tobacco substances and cannabinoids were having statistically significant impact on age of onset of schizophrenia.
 Conclusion: There was significant gender difference in age at onset of schizophrenia and substance misuse. Family history of schizophrenia eliminates the gender difference in age at onset of schizophrenia. Moreover non-tobacco substances and cannabinoids misuse can cause early onset of schizophrenia.
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