Credit card borrowing and the monoamine oxidase A (MAOA) gene

Using a discovery and replication sample from a U.S. representative data set, we show that a functional polymorphism on the MAOA gene is associated with credit card borrowing behavior. For the combined sample of approximately 12,000 individuals we find that having one or both MAOA alleles of the less transcriptionally efficient type raises the average likelihood of reporting credit card debt by about 4%. These results suggest that behavioral models benefit from integrating genetic variation and that economists should consider the welfare consequences of possible discrimination by lenders on the basis of genotype.