Nicotine Addiction
Nicotine, the most widely used addicting drug in U.S. society, affects the chemistry of the brain.
Information in the brain is transmitted between nerve cells by the neurotransmitter
acetylcholine. Acetylcholine is released from one cell and moves to the next cell, which it activates by fitting into a receptor. Nicotine, which resembles acetylcholine in shape, interferes with this process by fitting in the acetylcholine receptors, thereby stimulating the nervous system. This gives the smoker an initial physical lift. Acetylcholine returns to its point of origin once the information is processed, but nicotine stays attached to the acetylcholine receptor for a relatively long time, blocking normal information transmission and acting like a depressant. The brain then produces more acetylcholine and receptor sites to bring information transmission back to normal.
When not smoking, the smoker has too much acetylcholine and becomes nervous, hypersensitive, and anxious. Thus, when smokers describe smoking as relaxing, what is really happening is that smoking suppresses their nicotine symptoms. When a smoker quits, the brain takes one to two weeks to readjust the amount of acetylcholine back to normal levels. Some of the brain changes are believed to be permanent, which makes quitting smoking extremely difficult, and may explain why some people who have quit smoking for years quickly go back to their old smoking levels after a single
cigarette.
History of Smoking
American Indians smoked pipes, and European explorers had introduced the practice into the Old World by the early 16th century. By the late 19th century, tobacco use was widespread, but people used only small amounts. Cigarettes were rare, and so was lung cancer. These patterns began to change around the turn of the century. The growth of cigarette smoking is generally credited to three developments. The invention of the cigarette manufacturing machine enabled the tobacco industry to make cigarettes widely available at inexpensive prices. The spread of the safety match made lighting up easier and safer. Mass advertising enabled the tobacco industry to create specific images for cigarette smokers to emulate. The first target of tobacco advertising was male smokers, who were shown in ads as rugged and tough. The industry did not target women until the 1930s, showing glamorous and elegant women as central images. Before these developments the average American smoker smoked only 40 cigarettes each year; current smokers may smoke 40 cigarettes a day.
As the popularity of smoking increased, the rates of lung cancer and heart disease increased at parallel rates. By the early 1960s numerous clinical and laboratory studies on smoking and disease had been made. In 1964 a committee appointed by the surgeon general of the U.S. Public Health Service issued a report concluding that most lung-cancer deaths are caused by cigarette smoking. Later surgeon general's reports concluded that smoking caused chronic bronchitis, emphysema, and cardiovascular disease. These and other reports began to turn public opinion against smoking.
Health Effects
Besides nicotine, cigarette smoke consists of more than 4,700 chemical compounds, including cardiac poisons, cancer-causing agents, and industrial solvents, which can cause heart disease, strokes, lung diseases, cancer, and birth defects. Lung cancer and heart disease, once considered men's diseases, increased sharply in women as more began smoking. Inhaling the hot toxic fumes from the burning tobacco burns the linings of the air passages and reduces the smoker's ability to fight off disease. The large particles in smoke form a corrosive tar containing many poisonous chemicals. This tar collects in the lungs, exposing the smoker to these dangerous chemicals. A pregnant woman who smokes passes the toxic chemicals she takes in to the developing fetus, where the chemicals can cause a spontaneous abortion or can cause theby to have a lower birth weight or birth defects.
Chemicals in burning cigarette, pipe, or cigar tobacco also pollute the air as secondhand smoke, which contains formaldehyde, arsenic, cyanide, radioactive compounds, benzene, and carbon monoxide. A 1986 Surgeon General's report concluded that passive inhalation of smoke by nonsmokers caused lung cancer and respiratory problems. A 1992 study by the EPA confirmed the 1986 report, concluding that secondhand smoke, defined as smoke inhaled by a nonsmoker residing with a smoker, was a proved human carcinogen that caused 3,000 lung-cancer deaths a year in nonsmokers. The report also blamed secondhand smoke for up to 26,000 cases of asthma in children, 20% of annual asthma attacks in children, and 15,000 hospitalizations of children each year from respiratory problems. In 1997 the California Environmental Protection Agency confirmed the U.S. EPA's conclusions and added that secondhand smoke also caused heart disease, sudden infant death syndrome (SIDS), and retarded fetal growth, and linked it to spontaneous abortion, cervical cancer, and other diseases. Secondhand smoke kills about 37,000 people a year through heart disease alone. In 1995 former tobacco industry employees released industry documents indicating that the tobacco industry had known since the 1960s that nicotine was addictive and that smoking caused cancer.