Background: Schizophrenia is a widespread neurodegenerative disorder, which affects approximately 1% of the world population. It is a multifactorial and a highly heritable disease to which genetic factors contribute up to approximately 80%. Nowadays, multitude of genes have been discovered that relate to this disorder mostly by affecting the performance and levels of neurotransmitters in neural systems. Since PAI-1 is a considerable gene in the performance of neural systems, the present study dealt with the relationship between -675 4G/5G polymorphism in PAI-1 gene and schizophrenia among Iranian patients.

Materials and  Methods: This case-control study was carried out on 106 blood samples collected from individuals suffering from schizophrenia and 122 healthy controls. DNA was extracted from the samples and the frequency of the polymorphisms was analyzed using ARMS-PCR method. Finally, the products were detected on 2% agarose gel electrophoresis.

Results: The analysis of the data for -675 4G/5G polymorphism showed that 17.9% of the patients and 1.6% of the controls were mutant homozygous and 65.1% of the patients and 45.9% of controls were heterozygous. Also, 17% of the patients and 52.5% of the controls were normal homozygous.

Conclusion: There was a significant relationship between PAI-1 4G/5G polymorphism and the incidence of schizophrenia. To the best of our knowledge, this is the first study in Iran that assesses the frequency of the polymorphism among Iranian patients. However, further studies with more samples are necessary.