Genetics and addiction: biological mechanisms and inheritance

Substance Abuse

According to the American Psychological Association (Price, 2008) and the National Institute on Drug Abuse (2008), at least half of an individual's overall susceptibility to drug addiction can be traced to genetic factors. Researchers estimate that genetics account for a full 75% of a person's addiction to tobacco (Price, 2008). Studies on identical twins separated at birth have led to this claim, which revolutionizes research and understanding of substance abuse. One reason for the increased likelihood of addiction may be that some people are genetically predisposed to react a certain way to certain drugs; or are simply more sensitive to drugs ("Genetics," n.d.). Genes may determine whether a person reacts positively or negatively to a drug, leading to basic behavioral responses to drugs or alcohol. Furthermore, genetics might account for differential withdrawal symptoms.

The genetics of addiction are poorly understood and highly complex, given the wide variety of addictive behaviors and the confounding variables with regard to environmental triggers and extraneous genetic markers. It is unlikely that there is a single gene for addiction. It is also difficult to create reliable family genomes for addiction because there is no absolute definition for addiction; occasional drug use does not necessarily constitute addiction and anecdotal reports from grandparents could mislead researchers into labeling an ancestor as having a substance abuse problem. There are also concurrent psychiatric problems including depression and anxiety, which may predispose the individual to substance abuse and it is that underlying psychiatric condition that is inherited -- not the addiction itself. Therefore, it is important to define terms. It is also important to understand that addiction is not a clear-cut problem like a cancer or cystic fibrosis.

However, research does clearly show that genetic markers can predict a tendency of future generations to display abusive behavior. Knowing the importance of genetics on predicting future behavior can alert doctors and healthcare providers of risk factors and target at-risk individuals and families for preventative programs. Furthermore, genetic markers for addiction do not necessitate that an individual will develop a substance abuse problem. Coping skills account for the remainder of the factors, other than genes, that create impetus to use drugs. Research on the genetic components of addiction can also lead to the development of pharmaceuticals that address the underlying genetic factors that predispose someone to addiction. For instance, research in mice has revealed that serotonin receptor gene Htr1b is lacking in subjects that are more attracted to cocaine and alcohol ("Genes and Addiction," n.d.). Research has revealed other DNA sequences that point to specific tendencies toward, or aversion to, specific drugs.