Summary - Multifactorial quality has an important role in the aetiology of alcoholism. Psychological factors and social environment (primary family's systems of values, patterns of behaviour, exchange of emotions and communication, alcohol accessibility) influence the development of excessive drinking, but biological effects, i.e. genetic potential cannot be neglected either. There is a series of studies (twin, adoptive) elaborating connection and influence of genetic factor and social environment and some of them indicated a possible existence of the genetic component responsible for the development of excessive drinking and consequential alcohol dependency. In this paper, we have presented the existence of alcohol dependency in identical twins with established family heredity. (Alcoholism 2006;42:93-99)
Key words: Identical twins; Alcohol dependency; Family heredity
It has been noticed long ago that in some families, the development of alcohol dependency is more frequent. Over the last thirty or so years, the studies have been made confirming it.1'2 However, the question remains open whether this occurs due to the fact that children learn how to become an alcoholic from their parents and family environment or due to the fact that they inherit the genes with predisposition for alcohol dependency development.
When discussing the influence of social, i.e. family environment, certain important factors in the development of dependency should be taken into consideration. An alcoholic does not represent a stable identification model, i.e. role model for his child. The person who has grown up in unfavourable living conditions later on in life often becomes insecure and unsatisfied and often starts to drink in order to forget her/his problems. Also, the fact that children learn patterns of behaviour from their parents should not be forgotten. Finally, certainly the most important environmental factor for development of alcoholism is accessibility of alcohol - i.e. if alcohol is not accessible to a person and she/he does not drink it, she/he cannot become dependent.3
Various researches have been conducted looking for the possible genetic components responsible for the development of alcoholism. These researches include family and population studies in which the genetic, biochemical and neurobiochemical markers and characteristics are monitored.4'5 Two most often used types of studies for examining the heredity in alcoholism are twin and adoption studies.6
The twin studies compare the incidence of alcoholism in identical twins with its incidence in fraternal twins.7,8 If the genetic component is responsible for the development of alcoholism, then, in identical twins having the same genetic potential, equal developing or non-developing of alcohol dependency would be expected. In fraternal twins with different genetic potentials, that would not be the case. Somewhere along the lines of these conclusions is the study conducted by Pickens and collaborators who have studied 169 pairs of the same-sex twins, male and female, of whom at least one had been included in alcoholism treatment.9 In identical twins a greater concordance of alcoholism has been found than in fraternal twins. Also, greater concordance regarding detrimental use of alcohol has been found in identical male twins compared to identical female twins. In another study by Partanen and collaborators conducted in Finland on 902 male twins, conclusions have been made on the basis of results that the less serious patterns of drinking are less frequently inherited and vice versa, more serious patterns are more frequently inherited.10
The adoptive studies compare the children of alcoholics who have been adopted by and have been growing up in families in which there are no alcohol dependent persons with the children whose parents have not been alcoholics and who have been growing up in such an environment.11"13 If the genetic factors have the main role, then the adopted children of alcoholics should more often develop alcohol dependency as adults. …