Genes linked to alcoholism

In Melinda Beck's article in The Wall Street Journal from Wednesday 9 February 2011, the genetic predisposition to alcoholism is discussed.^[1]This topic is addressed in Option E 4.6 Discuss the causes of addiction, including genetic predisposition, social factors and dopamine secretion.

Alcoholism has long been thought be to passed from parents to children but is there a genetic link or has this been environmental exposure to alcohol consumption?   Ms Beck states that

"children of alcoholic parents are four times as likely to develop drinking problems as the general population. Sons of alcoholic fathers face up to nine times the usual risk.  Even babies of alcoholics adopted into nondrinking homes have nearly the same risk ofalcoholism as they would if they'd stayed with their biological parents, studies have shown. If one identical twin is an alcoholic, the other twin has a 76% risk of alcoholism too." 

This strongly suggests a genetic link.  But what is the genetic link? 

The genetic basis is quite difficult to establish as the condition of alcoholism is more complex than a single gene can determine.  The speed at which alcohol is metabolized by the liver as well as how stress, pleasure sensations and response to reward are handled by the brain may have a genetic basis.  Ms Beck relates that just under one half of East Asian populations possess alleles that cause the body to transform alcohol to acetaldehyde.  This chemical produces sensations of nausea and faster heart rates.  These symptoms provoke an aversion to alcohol consumption so these people avoid drinking.

Another step in the process of associating a genetic basis to alcoholism is the development of treatments targeting genetic expression.  Some alcoholics who possess different alleles for the expression of serotonin, a neurotransmitter related to emotions of happiness, respond to a serotonin receptor blocker drug and thus reduce the amount of alcohol they consumed.

Ms Beck clearly indicates that environmental influences and social pressures also complicate the picture of alcohol addiction.

In option E, students should be able to discuss how genetic predisposition, social factors and dopamine secretion may cause addiction to drugs.  The discussion can develop each point but should certainly contain counter arguments such as having the gene does not oblige someone to become alcoholic only gives a predisposition.

Social factors could include peer pressure, drug acceptance  and media influences.  Peer pressure occurs when friends or acquaintances exert acceptance on the basis of consumption of some drugs.  Teenagers want to feel included and may yield to such pressures.  Acceptance of a drug's presence in society makes availability much easier to obtain and consume.  Alcohol and smoking tobacco are some of the most socially acceptable drugs in European culture. How media demonstrates drug use may also have a large influence on addiction.  I can remember when advertisements for cigarettes were shown in cinemas as well on television.  These have been eliminated but smoking continues for many other reasons.

Dopamine secretion is related to pleasure sensations.  Many drugs provoke increase dopamine secretion thus causing more pleasurable feelings associated with the consumption of the drug.  Other drugs block the reuptake of dopamine from the synapse causing accumulation of the neurotransmitter in the synapse and so more pleasure sensations.  As the person feels uncomfortable and irritable when not taking the drug as dopamine levels eventually decline, cravings for the drug occur.  This is addiction.