The research to determine a connection between finasteride and alcohol was conducted at the George Washington University Medical Center. It only involved 83 subjects who were moderate social drinkers (not alcohol abusers) and prescribed Finasteride for hair loss. A portion of them reported drinking less after being on the drug.
At this point, scientists are not sure why this phenomenon occurred. One possibility is that Finasteride affects the neurosteroidal system which may be the locus which controls the drive for alcohol. Further research is needed to explore the relationship between Finasteride and alcohol interest.