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The Science of Addiction | Genetics and Addiction

Posted on March 25, 2012

The Science of Addiction | Genetics and Addiction

The scientific study of addictive behavior has led down many pathways. For decades, mice have been studied scientifically in the laboratory to find causative relationships for explaining addictive behavior in lab specimens. Genetically and neurologically, mice are very similar to humans. The entire setup of the brain is quite similar, utilizing the same neurotransmitters and receptors and protein; Mice have 20,000 – 25,000, about the same number as humans. The average mouse gene is about 85% similar to the corresponding human gene.

In the laboratory, mice strains have been bred to have remarkably similar addictive characteristics. Examples include strains exhibiting unique drug preferences, and/or demonstrating either increased or decreased sensitivity, tolerance, dependence and withdrawal symptoms in the use of alcohol or drugs. Just as each laboratory strain of mice models similar or identical addictive behaviors, the strains also share genetic commonalities. As a result of these findings, researchers have been looking to genetics as a significant causative component of addiction. Supporting the hypothesis that genes and addiction are related, there are the studies over recent decades that record “pedigrees” of addiction in some family groups. Most observers experienced in working with addicts are very familiar with the family histories of many addicts that show this recurring theme. As well, many individuals suffering the agonies of addiction can identify family members that have gone through similar travails.

Laboratory studies have generated many interesting genetic relationships to addiction: Some prominent genes that have been identified include a) the A1 allele of the dopamine receptor gene DRD2 is more common in people addicted to alcohol or cocaine, b) mice bred to lack the serotonin receptor gene Htr1b are more attracted to cocaine and alcohol, c) mice with low levels of neuropeptide Y drink more alcohol, whereas those with higher levels tend to abstain, and d) alcoholism is rare in individuals with two copies of the ALDH 2 gene variation. These are only a few of the variants identified as genetic adaptations that have a causal relationship with addictive behaviors. In fact, an abundance of genetic factors effecting addictive behavior keeps growing through scientific research.

One of the latest genetic factors to be identified was announced in January, 2011 by the Yale University School of Public Health. A lead scientist announced the discovery of an addiction “gene” that has been identified as associated with multiple addictive behaviors, such as alcoholism and drug abuse, in white women of European origin. This gene is located on chromosome 11 and is called PKNOX2; it is indicative of multiple dependencies among white women involving nicotine, alcohol, marijuana, cocaine, opiates and other drugs. The women with this gene were almost twice as likely as white men, black women, or black men to have two or more addictions. Altogether, the scientific research in genetics is contributing a rapidly expanding number of genetic influences relating to addiction.

It is also very clear from the decades of research into addiction that the study and treatment of addictive behaviors is extremely complex. Just as there have been many genetic variations identified as characteristic of addictive behavior, the treatment of addiction must take into account a huge variety in individuals for treatment. It is believed, however, that central to addiction is the limbic sector of the brain. The limbic system contains the “reward pathway”, and is responsible for human behaviors that include instincts, feeding, fighting, fleeing, and sexual behavior. Food, nurturing and social interaction are essential for the survival of human society. These factors were responsible for shaping reward pathways in our ancestors millions of years ago.

Once it appeared, the reward pathway was passed down from generation to generation through a process called natural selection. Because the reward pathway increased animals’ chance of reproducing, it was “selected” and transmitted through the generations. Over time, the reward pathway remained a central part of the brain located in the limbic region. And, it is believed, it is in this sector of the brain that addiction is anatomically based.

The challenge to modern science is to expand the knowledge of neurological and genetic factors in addiction, and to reconcile this scientific knowledge with the societal and personality aspects of addiction. The very complexity of the individual, and the societies and environments in which that individual lives, creates such a highly complex set of factors that science alone (to this date) has not found a “medical” solution to addiction. In fact, many scientists and and other students of addiction maintain that science and medicine alone cannot cure addictive behaviors.

For these reasons, there has been a parallel path in the study and treatment of addiction. It will be the purpose of these articles to use the structure and belief of social sciences, from history and anthropology to religion and the Twelve Step program, to shed further light on the mystery of addiction. With acknowledgment that genetics are a fundamental factor in addiction, it is necessary to go beyond pure science to truly understand addictive behaviors and to treat addiction in an effective and lasting manner. We have begun this discussion with an analysis of where we stand scientifically in the search for effective of addiction. It is now time to bring in other disciplines and strategies to bring a coherent and comprehensive understanding of the nature of addiction and the application of realistic strategies for bringing relief to those who suffer the agony of the addicts life. These articles are provided by Origins Drug and Alcohol Recovery Centers, an outstanding program for those in need.

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