Biological Factors

Excerpted from Chapter One: Theories of Addiction and Implications for Counselling in Alcohol & Drug Problems: A Practical Guide For Counsellors

On this page:

• Genetic Inheritance
• Tolerance and Physical Dependence

Genetic Inheritance

There is growing evidence that alcohol use is influenced by genetic factors (Alcohol Health and Research World, 1995; Shuckit, 1999). The strongest evidence comes from studies of family histories, twins and adopted children, different racial groups, and animals. Genetic factors seem to influence the ways in which humans respond to and metabolize alcohol, and seem to contribute to neurological dysfunctions common in people whose drinking problems begin at an early age (see the discussion of psychological factors, below). Genetic factors also appear to play a role in people’s use of tobacco and other drugs (Madden & Heath, 2002).

It is believed that many genes influence people’s responses to alcohol, and that their responses reflect a continuum of vulnerability to alcohol problems. This understanding is consistent with behavioural studies that have failed to clearly distinguish between people with drinking problems and others.

The influence of genetic factors is sometimes interpreted as meaning that, in those who are vulnerable, alcoholism is an inevitable, progressive and irreversible condition. This reflects a limited understanding of the role of genetics in determining complex behaviours, and is inconsistent with research. For example:

• There is overwhelming evidence that in both clinical and survey samples many people labelled “alcoholics” have periods of moderate drinking.
• Several early experiments showed that “alcoholics” are able to limit their drinking in laboratory settings when they view the benefits of reduced drinking as worthwhile. These experiments demonstrated the role of environmental factors (such as price) in moderating alcohol consumption, even among “alcoholics” (Mello & Mendelson, 1965; Mello et al., 1968).

Further, there are large differences between otherwise similar societies in consumption levels and rates of alcohol problems. For example, the per capita consumption of alcohol in Norway was only 5.64 litres per year in 1999, and Norway had a low rate of liver cirrhosis. In contrast, in France (where the gene pool is presumably largely the same), the per capita consumption of alcohol was 20.28 liters per year, and France had one of the highest rates of cirrhosis. Such differences also occur within the same society over time. Between 1945 and 1982, the rates of alcohol consumption and alcohol problems increased dramatically in many industrialized countries (Smart & Ogborne, 1996).

If genetics played a determining role in drinking, we would have to conclude that Norwegians have different genes from the French and that the gene pool of the industrialized world has changed dramatically since the end of the Second World War. Neither conclusion could be supported on other grounds, and neither conclusion is necessary because levels of drinking and of drinking problems are clearly influenced by social customs and economic forces. These same forces also influence the drinking behaviour of individuals.

Of course, this does not rule out the influence of genetics on drinking behaviour and alcohol problems. There are wide individual differences in preferences for alcohol and the capacity to drink large amounts, and genetic factors contribute to these differences. However, other factors are clearly important and need to be included in theoretical models.

Equally, the potential influence of genetic factors should be considered when counselling people with alcohol problems. This perspective can contribute to clients’ understanding of their problems and to their recovery. However, clinicians should ensure that clients also learn to recognize other factors that influence drinking, especially those factors that are within their own control.

Tolerance and Physical Dependence  

The repeated use of alcohol and other drugs can change the body’s ability to adapt to the presence of these substances. One result is that people become less sensitive to the substance and so need to increase the dosage to obtain the desired effects. This loss of sensitivity is called tolerance.

The body’s adjustment to the presence of a drug may also result in withdrawal symptoms when use stops. This condition is called physical dependence. In extreme cases, the effect of rapid withdrawal can be life-threatening, because the body has become so dependent on the drug that withdrawal interferes with normal bodily processes.

The adaptive changes that underlie tolerance and physical dependence are not yet fully understood. However, they seem to involve changes to metabolic pathways, cellular adaptation, activation of parallel biochemical systems and changes to the release of neurotransmitters. These changes may help explain why some people who use alcohol and other drugs heavily find it so difficult to stop.

Research on neurobiological aspects of drug use has led to the identification of many relevant structures and processes (e.g., drug-specific receptor sites in the brain and the effects of specific drugs and their metabolites on neurotransmitters). It has been suggested that all addictive behaviours may be the result of common physiological or biochemical actions in the brain, and a good deal of research is currently focused on the neurotransmitter dopamine. Some theorists have suggested that all pleasurable activities, including drug use, result from the release of dopamine in specific areas of the brain. Some animal research supports this view, but it is likely that other mechanisms are also involved.

Some addiction treatment services include education on the biological effects of drugs, in the belief that this will motivate clients to change their behaviour. However, there is little evidence that this type of drug education influences client outcomes (Health Canada, 1999).

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