•Drug naïve patients with schizophrenia exhibited greater degree of baseline DNA damage.
•The DNA repair capacity was preserved in the majority of cases.
•Age, gender and duration of untreated illness did not influence genomic damage or repair efficiency.
The etiology of schizophrenia continues to be confounding and elusive. Some knowledge gaps exist in the neurodegenerative theory of schizophrenia. Oxidative DNA damage and repair deficits are relevant to the mechanisms of neurodegeneration but have not been studied in drug naïve schizophrenia. The present study used the comet assay technique to study the extent of DNA damage in circulating peripheral lymphocytes of patients with drug naïve schizophrenia (n=40) along with an age and gender matched control group (n=40). We also assessed the DNA repair efficiency in cases following incubation in a nutrient medium. All the assayed comet parameters demonstrated significantly greater baseline DNA damage in cases in comparison to the controls except for head diameter (p<0.001 for all significant results, p=0.32 for head diameter). Gender, age and duration of illness (p=0.21, 0.69 and 0.12 respectively for tail length) did not influence any of the parameters significantly. Significant decrease was noted in the comet tail length and percentage of DNA in comet tail (p<0.001 for both) in cases following incubation suggesting that the DNA repair machinery was preserved. No difference in DNA repair efficiency was noted between the genders (p=0.23 for tail length). Our findings confirm the presence of significant baseline DNA damage in schizophrenia even prior to the initiation of anti-psychotic treatment. Additionally, intact genomic repair efficiency was noted in this group as a whole. These results provide some evidence for oxidative DNA damage as molecular link underpinning neurodegeneration in drug naïve schizophrenia.