This study aimed to investigate the possible association between T102C and –1438 G/A polymorphism in the 5-HT2A receptor gene and susceptibility to and clinical features of obsessive–compulsive disorder (OCD).

Fifty-eight patients with OCD and 83 healthy controls were included in the study. All patients were interviewed and rated by Yale-Brown Obsessive–Compulsive Scale. T102C and –1438 G/A polymorphisms of 5-HT2A receptor gene were determined by PCR technique in DNAs of peripheral leucocytes.

OCD patients and healthy controls did not show significant differences in genotype distribution for both polymorphisms investigated. We found that frequencies of the TT genotype for T102C polymorphism and the AA genotype for –1438 G/A polymorphism were significantly higher in patients with severe OCD compared to those with moderate or moderate–severe OCD.

The –1438 G/A and T102C polymorphisms of the 5-HT2A receptor gene are not associated with an increased risk of OCD. Our data suggest that the TT genotype of T102C and the AA genotype of –1438 G/A polymorphism might be a factor in clinical severity of OCD.

The aim of this study is to investigate whether there were any associations between the T102C and 1438 A/G polymorphisms of the 5-HT2A receptor gene and schizophrenia. We conducted a case–control study of the T102C and 1438 A/G polymorphisms in Turkish patients.

We compared genotypes and allele frequencies of T102C and 1438 A/G polymorphisms of 5-HT2A receptor gene in 102 patients with schizophrenia diagnosed, according to DSM-IV, and 107 healthy controls. Genotyping was performed by real-time polymerase chain reaction.

We found no significant association between schizophrenia and genotypic or allele frequencies of HTR2A gene 102T/C (rs6313) and 1438 A/G (6311) polymorphisms. However, comparison of HTR2A gene 102 T/C and 1438 A/G polymorphisms in terms of genotypic and allele frequencies between the two patient groups, with or without a family history of schizophrenia, shows that T- and A-allele frequencies were significantly higher (p < 0.05) in the case group that has a history of schizophrenia in their family.

In conclusion, our results do not support the hypothesis that the T102C and 1438 A/G polymorphisms in the 5-HT2A receptor gene are associated with schizophrenia, but further studies in a larger sample are needed.