Smoking, drinking and the brain: A neurodegenerative cocktail
Studies highlight the need to step up research on the role of alcohol and nicotine in brain development, neurodegeneration and effects on behaviour especially with chronic abuse.
Alcohol and tobacco are frequently used together and are usually considered as socially accepted drugs. However, both lead to drug dependence and, because of their numerous social and health-related consequences, they are a continuous source of national public policy debate.
There is little doubt that the majority of individuals who smoke tobacco do so in order to experience the reinforcing effects of nicotine present in smoke. The reasons why people start experimenting with alcohol and nicotine can be various but mostly are related to the drugs' ability to induce euphoria (a sense of well-being). Nicotine in low doses increases the ability to concentrate while low alcohol doses cause a decrease in the normal social inhibitory control of behaviour.
In higher doses, both drugs significantly depress the activity of the brain bringing about changes in mood, arousal and sedation. Both drugs are highly addictive and produce strong withdrawal effects on cessation. Furthermore, smoking and excessive alcohol consumption are risk factors for cardiovascular disease and for some form of cancer such as mouth, lung and throat cancers.
More than 4,000 chemical substances are generated by the chemical reactions that occur in the intense heat of a burning cigarette. A group of these chemicals, collectively known as tar, is carried into the lungs on inhaled smoke. The bloodstream then distributes the components of tar throughout the body where liver enzymes convert them into chemicals having carcinogenic properties. Compared with the risk for non-smokers/non-drinkers, the approximate relative risks for developing mouth and throat cancer are seven times greater for those who use tobacco, six times greater for those who use alcohol, and 38 times greater for those who use both tobacco and alcohol.
Recent studies have shown that both nicotine and alcohol cause severe brain damage especially in areas of the brain that control behaviour. Furthermore, alcoholics who smoke appear to damage their brains much more than alcoholics who do not smoke. It is already a well-known fact that the brains of long-term alcoholics shrink in size, but these new findings are the first evidence that cigarette smoking might contribute to this shrinkage. Experiments in our laboratories have also shown that nicotine, in doses equivalent to those found in the blood of heavy smokers, causes significant damage in an area of the brain that is very important for learning and memory formation.
The deleterious effects of alcohol on the brain in combination with cigarette smoking are extremely important. Approximately 90 per cent of alcoholics are also smokers and the more severe the tobacco habit is, the greater the brain damage, especially in adolescents when the brain is still developing. There is also the problem of binge drinking, where alcohol is consumed in large quantities in a considerable short period of time, during which the body, including the brain, tries to counteract the high concentration of toxins present. It is worth mentioning that the body takes about two hours to break down a bottle of beer, a glass of wine or a shot of vodka. If alcohol consumption occurs at a faster rate than the body can break down, the excess will remain in the bloodstream, travelling to the brain.
Unfortunately, it takes a considerable number of years until the first symptoms of brain damage begin to show. The adult human brain weighs approximately 1.4 kg and contains about 100-150 billion brain cells of which several thousands are lost every single day. These, unlike other cells in the rest of the body, are not replaced. So, as we grow older, the loss accumulates and anything that accelerates this process will have a profound effect on the functions of the brain later on in life. Indeed, heavy alcohol consumption during teenage years not only predicts lower scores in memory and attention tests in later years but also increases significantly the chances of developing brain disorders characterised by severe long-lasting memory impairment.
These results seriously question the legal use of alcohol and tobacco smoking as social drugs, especially considering the fact that their addiction and withdrawal effects are not very different from those of other drugs of abuse considered as illegal, such as cocaine and heroin. Indeed, all of these drugs share common biological pathways, in most cases affecting the same brain regions controlling reward and reinforcement. These studies also highlight the need to step-up research on the role of alcohol and nicotine in brain development, neurodegeneration and effects on behaviour especially with chronic abuse.
• Dr Scerri is lecturer in neuropathology at the University of Malta.
There is little doubt that the majority of individuals who smoke tobacco do so in order to experience the reinforcing effects of nicotine present in smoke. The reasons why people start experimenting with alcohol and nicotine can be various but mostly are related to the drugs' ability to induce euphoria (a sense of well-being). Nicotine in low doses increases the ability to concentrate while low alcohol doses cause a decrease in the normal social inhibitory control of behaviour.
In higher doses, both drugs significantly depress the activity of the brain bringing about changes in mood, arousal and sedation. Both drugs are highly addictive and produce strong withdrawal effects on cessation. Furthermore, smoking and excessive alcohol consumption are risk factors for cardiovascular disease and for some form of cancer such as mouth, lung and throat cancers.
More than 4,000 chemical substances are generated by the chemical reactions that occur in the intense heat of a burning cigarette. A group of these chemicals, collectively known as tar, is carried into the lungs on inhaled smoke. The bloodstream then distributes the components of tar throughout the body where liver enzymes convert them into chemicals having carcinogenic properties. Compared with the risk for non-smokers/non-drinkers, the approximate relative risks for developing mouth and throat cancer are seven times greater for those who use tobacco, six times greater for those who use alcohol, and 38 times greater for those who use both tobacco and alcohol.
Recent studies have shown that both nicotine and alcohol cause severe brain damage especially in areas of the brain that control behaviour. Furthermore, alcoholics who smoke appear to damage their brains much more than alcoholics who do not smoke. It is already a well-known fact that the brains of long-term alcoholics shrink in size, but these new findings are the first evidence that cigarette smoking might contribute to this shrinkage. Experiments in our laboratories have also shown that nicotine, in doses equivalent to those found in the blood of heavy smokers, causes significant damage in an area of the brain that is very important for learning and memory formation.
The deleterious effects of alcohol on the brain in combination with cigarette smoking are extremely important. Approximately 90 per cent of alcoholics are also smokers and the more severe the tobacco habit is, the greater the brain damage, especially in adolescents when the brain is still developing. There is also the problem of binge drinking, where alcohol is consumed in large quantities in a considerable short period of time, during which the body, including the brain, tries to counteract the high concentration of toxins present. It is worth mentioning that the body takes about two hours to break down a bottle of beer, a glass of wine or a shot of vodka. If alcohol consumption occurs at a faster rate than the body can break down, the excess will remain in the bloodstream, travelling to the brain.
Unfortunately, it takes a considerable number of years until the first symptoms of brain damage begin to show. The adult human brain weighs approximately 1.4 kg and contains about 100-150 billion brain cells of which several thousands are lost every single day. These, unlike other cells in the rest of the body, are not replaced. So, as we grow older, the loss accumulates and anything that accelerates this process will have a profound effect on the functions of the brain later on in life. Indeed, heavy alcohol consumption during teenage years not only predicts lower scores in memory and attention tests in later years but also increases significantly the chances of developing brain disorders characterised by severe long-lasting memory impairment.
These results seriously question the legal use of alcohol and tobacco smoking as social drugs, especially considering the fact that their addiction and withdrawal effects are not very different from those of other drugs of abuse considered as illegal, such as cocaine and heroin. Indeed, all of these drugs share common biological pathways, in most cases affecting the same brain regions controlling reward and reinforcement. These studies also highlight the need to step-up research on the role of alcohol and nicotine in brain development, neurodegeneration and effects on behaviour especially with chronic abuse.
• Dr Scerri is lecturer in neuropathology at the University of Malta.