Objectives: Certain components of the serotonin system have been known for some time to be risk factors for schizophrenia. Few studies have, however, focused on the association between the therapeutic responses to atypical antipsychotics, such as risperidone, and polymorphisms of the 5-HT3 receptor, the only ionotropic ligand-gated serotonin receptor, even though there have been some genetic clues linking HTR3A and schizophrenia. We therefore postulated that such a polymorphism might be an explanatory factor in the diversity of response to risperidone treatment.
Methods: The study recruited 107 drug-naive Chinese schizophrenia patients who were given 8 weeks of risperidone monotherapy and it explored three of four single nucleotide polymorphisms spanning HTR3A for possible association with therapeutic improvement, using the Positive and Negative Symptom Scale.
Results: Significant correlation between the baseline score and therapeutic improvement was observed in each subscale (P<0.001). Statistical analysis revealed association between genotypes of g.14396A>G polymorphism (rs1176713) and score reductions of negative and general subscales after adjusting for the influence of the baseline scores of each subscale [P (F, d.f.)=0.026 (3.763, 2), 0.023 (3.937, 2) respectively]. One haplotype, C-A-G, contributed to an effective response in general symptoms (chi(2)=7.3, P=0.007, odds ratio=3.371).
Conclusion: The results of this study are the first to suggest that the polymorphism of HTR3A may be a useful predictor of therapeutic response to risperidone treatment in Chinese schizophrenic patients, although these conclusions should be treated with caution because of the intricacy of the variety of the therapeutic effects to risperidone.