The Science Behind Smoking (Module 5)

Background

Tobacco is a very potent substance. It contains more than 4,000 chemicals, many of which are released during smoking. Tar and carbon monoxide are two particularly dangerous chemicals in cigarette smoke. Tar can cause lung cancer, emphysema, and bronchial diseases, while carbon monoxide can cause heart problems. Other serious health problems linked to smoking include digestive cancers, gastric ulcers, and cancers of the throat, tongue, lip, esophagus, and pancreas.

In addition to dangerous substances like tar and carbon monoxide, the leaves of the tobacco plant contain a drug called nicotine. Nicotine is found in all tobacco products: cigarettes, cigars, pipe tobacco, chewing tobacco, and snuff. It is a strong drug that acts on the nervous system. It also causes an increase in blood pressure, heart rate, and respiration. Nicotine is very addictive. It is what causes people to continue to smoke, even though they know the health consequences of doing so.

Different drugs have various effects on the body. People take drugs because of the feeling of euphoria they experience as the drugs change the way the brain normally works. Some of the changes that happen in the brain following drug use are short-term, while other changes can last a long time.

Prolonged drug use can change the brain in such a way that addiction results. Addiction is a disease that is characterized by changes in the structure and functioning of the brain. Addiction results in:

• A strong compulsion or need to use drugs despite negative consequences (someone keeps using drugs even though he or she is having problems);
  
• Loss of control over the amount of the drug used (someone uses more than he or she plans) and other drug-related behavior (someone does or says things he or she would not ordinarily say or do);
  
• Intense craving for the drug when it is not available. This craving is due to changes in the brain. Once a person is addicted, he or she must have the drug just to keep from feeling bad. This is because drugs can cause changes in the functioning of neurotransmitters in the brain.
  
  

When a person stops using a drug, it takes a while for the brain to get back to normal. During that time, the person may feel bad and have an intense craving for the drug. Research in animals and some humans is beginning to suggest that some drugs may cause changes that are permanent. Addiction is considered a disease because the drugs have changed the normal functioning of the brain. Addiction can be successfully treated. However, the best way to avoid addiction is to never start using drugs.

Scientists are not exactly sure why nicotine is addictive, but they have a good hypothesis. The nicotine molecule is shaped like a neurotransmitter, acetylcholine. Acetylcholine and its receptors are involved in many functions, including muscle movement, breathing, heart rate, and learning. Acetylcholine also causes the release of other neurotransmitters and hormones that affect mood, appetite, and memory. When nicotine gets into the brain, it attaches to acetylcholine receptors and mimics its actions, overstimulating the brain.

Nicotine also activates areas of the brain that are involved in producing feelings of pleasure and reward by raising the levels of another neurotransmitter, dopamine. Increased levels of dopamine produce the strong, pleasurable feelings that lead to nicotine addiction. In fact, nicotine is so addictive that it is usually very hard for people to quit using tobacco products. When smokers do try to stop, they often experience cravings for cigarettes, anger, frustration, irritability, restlessness, anxiety, fatigue, headaches, and depression.

Nicotine enters the body very rapidly. After the smoke is inhaled, it takes only 8 seconds to reach the brain. Within about 40 minutes, half of the effect of nicotine is lost. This is the reason people feel the need to smoke another cigarette. Therefore, many smokers light up a cigarette about every 40 minutes. These smokers almost always have measurable amounts of nicotine and carbon monoxide in their bodies.

There are 1.1 billion smokers in the world, and they smoke 6 trillion (6,000,000,000,000) cigarettes each year, according to the World Health Organization. According to the U.S. Centers for Disease Control and Prevention, there are about 47 million adult cigarette smokers and 12 million tobacco “chewers,” or users of smokeless tobacco, in this country. More than 430,000 people die each year from tobacco use. Because people do have control over whether they begin to smoke, smoking can be viewed as the most preventable cause of death in the United States.