The claim proving the evidence of genetic components that are from the affect of Native Americans substances differences from rest of the world, are all around true. The source listed does correctly state the linkage through genes that have been identified as chromosomal regions in "substance dependence" relating to ones traits, such as body mass, drug tolerance, EEG patterns and externalizing behaviors. The sources credible researchers have found that this is "a significant health issue to many communities influences approximately 50% of the risk observed within a general population". Affecting half or more of the population makes the effect of the statement real and alive. There researchers are credible and trained doctors that are licensed to study medicine and science, through investigation of the source through universities and labs placed across the United States. Since the source of a national website used for medicine, it is credited with all true publishments by the world, and helped for many to educated across the globe.
Another National source, "National Institue of Drug Abuse", further supports this claim from the U.S. Federal Agency for specifically scientific research on drug abuse and addiction. There trained researchers explained that they have found more evidence on this topic, and now find that "genetic factors account for about 40%, and up to 60%, of of addiction due the the genes in there genetics group, including Native Americans". This other federal source confirms that genes are linked to addiction risk, in more good ways than bad, unfortunately.
Source:
https://nida.nih.gov/research-topics/prevention