I've heard that alcoholism and/or addiction is heredity, and I have seen that in some families. It may not affect every member of a family, only some. I have often wondered why some become alcoholics or addicts, and others don't.
If Celiac's is considered a disease, then by the same measure alcoholism is a disease.
Celiac's can live a healthful, normal life if they don't ingest wheat products, which destroy the vilii of the intestines leading to chronic digestive and other wide ranging physiological complications. Stop ingesting wheat, and all goes back to normal.
Celiac's is a disease, a genetic disease. You have to have the gene for celiac disease to manifest. Just because you have the gene, does not necessarily mean you will have celiac's. You can go several years eating gluten products and have absolutely no problem, then something could trigger it, and bam, you have a intolerance to gluten. Or, you can carry the gene, and never have a reaction to gluten.
If you don't have the gene for celiac's, you will never have celiac's disease. You can carry the gene for celiac's and be unaware they have it, until and unless you have a reaction to gluten.
So is addiction and/or alcoholism caused by a gene? If you don't have the gene for addiction/alcoholism, you can drink and drug as much as you want and won't become an addict or alcoholic?
Part of the definition of disease from Webster's is "inherent weakness, or environmental stress, a condition or tendency, as of society, regarded as abnormal and harmful".