Medical experts believe alcoholism stems from a combination of genetic and environmental factors. A strong genetic contribution to alcoholism shows in the three- to four-fold higher risk for alcoholism among first-degree relatives of an alcoholic compared to those without such a family history, reports the University of Minnesota Department of Psychology. Understanding the genetic factors related to alcoholism is a first step to discovering how to prevent or treat the illness.
Neurotransmitter Systems
People grappling with alcoholism tend to be addicted to other substances as well, such as cigarettes, and exhibit greater risk-taking behaviors. This addictive type of personality can be passed down in the genes. Addiction has been linked to neurotransmitter imbalances, which may also be inherited.
One neurotransmitter pathway believed to be centrally involved in the action of additive drugs is the mesolimbic dopamine system, which is associated with the ability to feel pleasure. Alcohol-induced changes in neurotransmitter systems are also believed to play a role in the development of tolerance to alcohol, according to the book "Genetic Influences on Neural and Behavioral Functions."
Various Chromosomal Loci
Specific areas on various chromosomes are likely to be involved in the genetic contribution to alcoholism. Humans have 46 chromosomes, or 23 pairs. One chromosome from each pair is inherited from the mother and the other comes from the father. Chromosomes are numbered 1 through 22, with the 23rd pair being the sex chromosomes X and Y. Genes located on these chromosomes determine all of our traits, from hair color to shoe size.
A study published in the "American Journal of Psychiatry" looked for chromosomal locations, or loci, in siblings who had alcoholism with or without depression that could be responsible for these conditions. They concluded that a gene or genes on chromosome 1 may predispose some people to alcoholism and may also increase the risk for depression. Loci on several other chromosomes are also likely to play a role in alcoholism, and it may be that polygenicity, or the combined action of more than one genetic locus, underlies the genetic contribution to alcoholism.
Event-Related Brain Potentials
Event-related brain potentials (ERPs) are recordings of brain activity made from electrodes on the scalp. Altered ERPs are seen in people with a variety of psychiatric disorders, including alcoholism. Family members of people with altered ERPs run a higher risk of also having altered ERPs than the general population, suggesting a genetic link to ERPs.
A specific alteration of ERP, called a reduction of amplitude of the P3 component, has been seen in alcoholics and their offspring. A study published in the "American Journal of Human Genetics" found a significant genetic influence on the P3 amplitude, specifically implicating locations on chromosomes 4 and 5.
References
- University of Minnesota Department of Psychology: Is Alcoholism Genetic?
- "Genetic Influences on Neural and Behavioral Functions"; Donald Pfaff; 2000
- "American Journal of Psychiatry"; Evidence for a Locus on Chromosome 1 That Influences Vulnerability to Alcoholism and Affective Disorder; J.I. Nurnberger et al; 2001
- Online Mendelian Inheritance in Man: Alcohol Dependence
- "American Journal of Human Genetics"; Genetics of Event-Related Brain Potentials in Response to a Semantic Priming Paradigm in Families with a History of Alcoholism; L. Almasy et al; 2001
