For some people, using any amount of tobacco can quickly lead to nicotine dependence. Signs that you may be addicted include:

• You can't stop smoking. You've made one or more serious, but unsuccessful, attempts to stop.
• You experience withdrawal symptoms when you try to stop. Your attempts at stopping have caused physical and mood-related symptoms, such as strong cravings, anxiety, irritability, restlessness, difficulty concentrating, depressed mood, frustration, anger, increased hunger, insomnia, constipation or diarrhea.
• You keep smoking despite health problems. Even though you've developed health problems with your lungs or your heart, you haven't been able to stop.
• You give up social or recreational activities in order to smoke. You may stop going to smoke-free restaurants or stop socializing with certain family members or friends because you can't smoke in these locations or situations.

Nicotine is the chemical in tobacco that keeps you smoking. Nicotine is very addictive when delivered by inhaling tobacco smoke into the lungs, which quickly releases nicotine into the blood allowing it to get into the brain within seconds of taking a puff. In the brain nicotine increases the release of brain chemicals called neurotransmitters, which help regulate mood and behavior.

Dopamine, one of these neurotransmitters, is released in the "reward center" of the brain and causes improved mood and feelings of pleasure. Experiencing these effects from nicotine is what makes tobacco so addictive.

Nicotine dependence involves behavioral (routines, habits, feelings) as well as physical factors. These behavioral associations with smoking may act as triggers — situations or feelings that activate a craving for tobacco, even if you have not smoked for some time.

Behaviors and cues that you may associate with smoking include:

• Certain times of the day, such as first thing in the morning, with morning coffee or during breaks at work
• After a meal
• Drinking alcohol
• Certain places or friends
• Talking on the phone
• Stressful situations or when you're feeling down
• Sight or smell of a burning cigarette
• Driving your car

To overcome your dependence on tobacco, you need to become aware of your triggers and develop a plan to deal with the behaviors and routines that you associate with smoking.

Anyone who smokes or uses other forms of tobacco is at risk of becoming dependent. Factors that influence who will use tobacco include:

• Genetics. The likelihood that you will start smoking and keep smoking may be partly inherited — genetic factors may influence how receptors on the surface of your brain's nerve cells respond to high doses of nicotine delivered by cigarettes.
• Home and peer influence. Children who grow up with parents who smoke are more likely to become smokers. Children with friends who smoke also are more likely to try cigarettes. Evidence suggests that smoking shown in movies and on the Internet can encourage young people to smoke.
• Age. Most people begin smoking during childhood or the teen years. The younger you are when you begin smoking, the greater the chance that you'll become a heavy smoker as an adult.
• Depression or other mental illness. Many studies show an association between depression and smoking. People who have depression, schizophrenia, post-traumatic stress disorder (PTSD) or other forms of mental illness are more likely to be smokers.
• Substance use. People who abuse alcohol and illegal drugs are more likely to be smokers.

Tobacco smoke contains more than 60 known cancer-causing chemicals and thousands of other harmful substances. Even "all natural" or herbal cigarettes have chemicals that are harmful to your health.

Smoking harms almost every organ of your body and impairs your body's immune system. About half of all regular smokers will die of a disease caused by tobacco.

Women smokers are now at equal risk to men smokers of dying from lung cancer, COPD and cardiovascular disease caused by using tobacco.

The negative health effects include:

• Lung cancer and other lung diseases. Smoking causes nearly 9 out of 10 lung cancer cases. In addition, smoking causes other lung diseases, such as emphysema and chronic bronchitis. Smoking also makes asthma worse.
• Other cancers. Smoking is a major cause of cancers of the esophagus, larynx, throat (pharynx) and mouth and is related to cancers of the bladder, pancreas, kidney and cervix, and some leukemias. Overall, smoking causes 30 percent of all cancer deaths.
• Heart and circulatory system problems. Smoking increases your risk of dying of heart and blood vessel (cardiovascular) disease, including heart attack and stroke. Even smoking just one to four cigarettes daily increases your risk of heart disease. If you have heart or blood vessel disease, such as heart failure, smoking worsens your condition. However, stopping smoking reduces your risk of having a heart attack by 50 percent in the first year.
• Diabetes. Smoking increases insulin resistance, which can set the stage for the development of type 2 diabetes. If you have diabetes, smoking can speed the progress of complications, such as kidney disease and eye problems.
• Eye problems. Smoking can increase your risk of serious eye problems such as cataracts and loss of eyesight from macular degeneration.
• Infertility and impotence. Smoking increases the risk of reduced fertility in women and the risk of impotence in men.
• Pregnancy and newborn complications. Mothers who smoke while pregnant face a higher risk of miscarriage, preterm delivery, lower birth weight and sudden infant death syndrome (SIDS) in their newborns.
• Cold, flu and other illnesses. Smokers are more prone to respiratory infections, such as colds, flu and bronchitis.
• Weakened senses. Smoking deadens your senses of taste and smell, so food isn't as appetizing.
• Teeth and gum disease. Smoking is associated with an increased risk of developing inflammation of the gum (gingivitis) and a serious gum infection that can destroy the support system for teeth (periodontitis).
• Physical appearance. The chemicals in tobacco smoke can change the structure of your skin, causing premature aging and wrinkles. Smoking also yellows your teeth, fingers and fingernails.
• Risks to your family. Nonsmoking spouses and partners of smokers have a higher risk of lung cancer and heart disease compared with people who don't live with a smoker. If you smoke, your children will be more prone to SIDS, worsening asthma, ear infections and colds.