Genetic susceptibility to Tardive Dyskinesia in chronic schizophrenia subjects: I. Association of CYP1A2 gene polymorphism

Understanding the pharmacogenetic basis of developing iatrogenic disorders such as Tardive Dyskinesia (TD) has significant clinical implications. CYP1A2, an inducible gene of the cytochrome P450 family of genes, has been suggested to contribute to the metabolism of typical antipsychotics in subjects with schizophrenia on long-term treatment, and has been considered as a potential candidate gene for development of TD. In this study, we have investigated the significance of CYP1A2 gene polymorphisms in TD susceptibility among chronic schizophrenia sufferers (n=335) from north India. TD was diagnosed in approximately 29% (96/335) of these subjects. Of the 96 TD positives, 28 had been treated with typical antipsychotics alone, 23 with atypical antipsychotics alone and 45 patients had received both classes of drugs during the course of their illness. Out of the six SNPs tested, CYP1A2(*)2, (*)4, (*)5, (*)6 were found to be monomorphic in our population. CYP1A2(*)1C and CYP1A2(*)1F were polymorphic and were analyzed in the study sample. Since these two allelic variants lead to lesser inducibility among smokers, the smoking status of TD patients was also considered for all subsequent analysis. We observed increased severity of TD among TD-Y smokers, who were carriers of CYP1A2(*)1C (G>A) variant allele and had received only typical antipsychotic drugs (F(1,8)=9.203, P=0.016). No significant association of CYP1A2(*)1F with TD was observed irrespective of the class of drug they received or their smoking status. However, we found a significant association of CYP1A2(*)1F with schizophrenia (chi(2)=6.572, df=2, P=0.037).

Clinical and familial correlates of tardive dyskinesia in India and Israel

BACKGROUND

Antipsychotic drugs are widely used for the treatment of psychosis, especially schizophrenia. Their long-term use can result at times in serious side-effects such as Tardive Dyskinesia (TD). Since over 80% of schizophrenia sufferers (lifetime prevalence 1%) receive long-term antipsychotic drug treatment, the extent of the problem is potentially large. Increasing age is the most consistently demonstrated risk factor for TD.

AIMS

To assess effect of different clinical factors and demographic variables in India and Israel and sib pair concordance of Tardive Dyskinesia (TD) in India.

SETTINGS AND DESIGN

The study was conducted simultaneously among Indian and Israeli subjects: ascertainment was family-based in India and hospital-based in Israel.

METHODS AND MATERIAL

In India the instruments used were: Diagnostic Interview for Genetic Studies (DIGS), Positive and Negative Syndrome Scale (PANSS), Abnormal Involuntary Movement Scale (AIMS), and Simpson Angus Scale (SAS). The last three instruments were also used in Israel.

STATISTICAL ANALYSIS

Regression analysis and Pearson's correlation.

RESULTS AND CONCLUSIONS

TD symptoms were present in 40.4% of 151 Israeli subjects and 28.7% of 334 Indian subjects. While age at onset and total scores on PANSS were significant predictors of TD in both the samples, lower scores on the Global Assessment of Functioning Scale (GAF), diagnostic sub-group and male gender were significant predictors among Indians. There was no concordance of TD symptoms among 33 affected sib-pairs from India.