Smoking was thought to be a harmless form of relaxation when cigarettes were invented. Many people smoked and it was only later in their lives that the health threat of smoking was discovered. By then younger people had taken up smoking to copy their elders. It made the younger people feel more grown up.

Many of these people did not give up as they got older even though they knew the risks because they were affected by a chemical in the cigarette called nicotine. This chemical changes the person's behaviour. It makes them need a certain amount of nicotine to feel well. If they cannot get enough nicotine they feel ill.

People who feel like this have become addicted to the nicotine and many find it very difficult to stop smoking. In the meantime more young people copy them and begin smoking to make themselves feel grown up. Some of them become addicted too so the number of people smoking and putting their health at risk increases.

It is now known that smoking can greatly damage health and even kill. The nicotine causes the heart to beat faster and puts extra strain on it which can lead to a heart attack. The smoke contains a gas called carbon monoxide, which stops the blood in the lungs picking up oxygen from the air. There smoke also contains tar, which coats the lungs and airways, and makes it easier for germs to infect them. Over forty chemicals in the smoke can cause cancers to develop in the lungs and airways.

Alcohol has been made by people for thousands of years. It is intended to be drunk for relaxation, but if too much is drunk it affects the nervous system and a person's behaviour changes. They are much slower to respond than normal and may become aggressive or very sad. If large amounts of alcohol are drunk a person may become unconscious. In this state they may be sick, and are in danger of choking to death.

Alcohol is an addictive substance and some people who drink large amounts regularly become addicted to it. The liver is the organ in the body which breaks down alcohol into harmless substances. If large amounts of alcohol are drunk regularly for a long time the liver may be permanently damaged and the person may die.

Drug taking is a more recent problem but can be just as deadly as smoking and drinking too much alcohol. The chemicals in many drugs are addictive, and people who take them soon become addicted to them. People who become addicted to alcohol and drugs often stop taking care of themselves properly. They do not eat a balanced diet and they do not take regular exercise this in turn leads to poor health.