Researchers analyzed the data via an international genetic association meta-analysis consortium (the GWAS & Sequencing Consortium of Alcohol and Nicotine use). This involved comparing participants' genetic variants to five known substance use phenotypes, a term that refers to "the observable physical properties of an organism," such as an organism's appearance, development and behavior, according to Nature.com. An organism's phenotype is determined by its genotype, or the set of genes it carries plus any environmental factors that may influence their genes.
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The following five characteristics or phenotypes examined, based on decades of research:
- age of initiation of smoking
- number of cigarettes per day
- whether participant has ever been a regular smoker
- whether participant has ever quit smoking
- number of alcoholic drinks per week
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Scientists ultimately discovered 566 genetic variants in 406 loci (or fixed positions on a chromosome) associated with initiation, cessation and heaviness of tobacco and alcohol use. Of the 406 loci, 150 were considered pleiotropic, meaning they showed evidence for association with two or more of the five characteristics.
An increased risk for smoking was associated with an increased risk for a multitude of health conditions, such as obesity and coronary artery disease. The genetic risk for alcohol use, on the other hand, was associated with lower disease risk.
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While authors noted the meta-analysis of their variants is mostly highly reliable, “our substance use measures likely suffer from greater unreliability than some classical complex phenotypes such as height, years of education, or schizophrenia,” they wrote. Future researchers, they add, should work with more precise measures.
But these results, researcher Scott Vrieze said, "provide a solid starting point to evaluate the effects of these loci in model organisms and more precise substance use measures. We hope the results drive research on how these genes affect addiction and, ultimately, inform treatment development."
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According to the Atlanta-based Centers for Disease Control and Prevention, smoking is the leading cause of preventable death in the United States. More than 480,000 Americans deaths per year are attributed to cigarette smoking causes. Smokers are more likely than nonsmokers to develop heart disease, stroke and lung cancer.
The habit, which the World Health Organization deems one of the biggest public health threats in the world, costs the U.S. billions of dollars each year. And in Georgia, according to a recent report, the lifetime cost of smoking per smoker in the state totals $1,396,882.
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Excessive alcohol consumption, which also increases the risk of multiple health conditions, led to about 88,000 deaths annually between 2006-2010. In addition to immediate risks such as motor vehicle crashes, risky sexual behaviors, violence and alcohol poisoning, excessive use can lead to the development of chronic diseases and conditions, such as heart disease, mental health problems, alcoholism, cancers and dementia.
The country's estimated economic cost of binge drinking, according to 2010 CDC data, was $249 billion.
Read the full study at Nature.com.