Whether or not alcoholism and drug addiction are genetically determined is beside the point. Most people speak of alcoholism "running in the family," but there is, to date, no credible evidence that this is true. Which in and of itself does not matter, for drinking and drugging are NOT diseases, but behaviors, and therefore are CHOICES. So even if medical Science discovers this hangover gene, it has no bearing whatsoever on whether or not a person can control how much alcohol / drugs they voluntarily ingest.