Association of dopamine receptor D2 TaqI A polymorphism and cannabis use disorder in Lagos, Nigeria.

Abstract

TaqI A polymorphism (rs1800497) has been linked to many substance use disorders but there is a shortage of data on cannabis use disorder. Nigeria has a huge burden of cannabis use disorder, prompting our investigation of the relation between cannabis use disorder and the TaqI A polymorphism among males in Lagos, Nigeria. We recruited 106 males with cannabis use disorder based on International Classification of Diseases, version 10 (ICD-10) and 98 cannabis-naive males for the study. Cannabis use disorder was assessed using the Severity of Dependence Scale (SDS) and Cannabis Use Disorder Identification Test (CUDIT). Genotyping was done using the Restriction Fragment Length Polymorphism (RFLP). The frequency of the A1 allele was higher among the cannabis users (57.8%) compared with the nonusers (42.2%). The genotype distribution was found to be in Hardy-Weinberg equilibrium in both populations. The homozygous A1 genotype alone contributed 11.8% to the variance in the SDS scores. However, both A1/A1 and A1/A2 genotypes contributed to the variance in the CUDIT scores (10.2% and 5.1%, respectively). In conclusion, the distribution of the A1 allele among the general population in this study correlates with the previously reported findings in a southwestern Nigerian population. We also found that carrying an A1 allele appears to be a significant predictor of cannabis use disorder. The result suggests that carrying just a single allele of the A1 is enough to predict cannabis abuse, as shown by the allele association with CUDIT scores. However, double A1 alleles seem to be necessary for the prediction of dependence.