Smokers' Brains Change in Response to High Levels of Nicotine

February 24, 2012

Dear Mayo Clinic:

Is it true that smoking changes your brain somehow, making it harder to stop smoking? If so, how does that happen? Is there anything that can be done to change it back?

Answer:

Yes, that's true. When you smoke, your brain changes in response to the very high levels of nicotine delivered by cigarettes. Those brain changes cause you to become addicted to nicotine, and that addiction can make stopping smoking very difficult.

Nicotine is the chemical in tobacco that keeps you smoking. Nicotine that gets into your body through cigarettes activates structures normally present in your brain called receptors. When these receptors are activated, they release a brain chemical called dopamine, which makes you feel good. This pleasure response to dopamine is a big part of the nicotine addiction process.

Over time, as you continue to smoke, the number of nicotine receptors in your brain increases. Addicted smokers have billions more of these receptors than nonsmokers do. But not all smokers have such a high level of receptors. That is why some regular smokers can stop smoking without much difficulty.

When you try to stop smoking, the receptors in your brain do not receive nicotine, so the pleasure response is cut off. In addition, low�levels of nicotine lead to symptoms of nicotine withdrawal, such as strong cravings for a cigarette, anxiety, irritability, restlessness, difficulty concentrating, depressed mood, frustration, anger, increased hunger and difficulty sleeping. The fastest way to alleviate the withdrawal symptoms is to smoke a cigarette, which releases dopamine and activates the pleasure response.

To make stopping smoking even more difficult, the brain receptors can be conditioned to expect nicotine in certain situations long after you have stopped smoking. For example, if you regularly smoke when you drink alcohol, or when you are in a stressful situation, or after a meal, the nicotine receptors in your brain anticipate the dopamine rush from nicotine at that time. These "trigger" situations can cause intense cravings for a cigarette, even if you have stopped smoking for several months.

The good news is that once you stop smoking entirely, the number of nicotine receptors in your brain will eventually return to normal. As that happens, the craving response will occur less often, won't last as long or be as intense and, in time, will fade away completely.

Because of its effects on your brain, nicotine can be powerfully addictive. For many people, overcoming nicotine addiction and successfully dealing with its withdrawal symptoms requires medical treatment. Medications are available that can help reduce withdrawal symptoms, while support and guidance from a tobacco dependence treatment program can help you learn how to change your behavior in ways that increase your chances of staying smoke-free.

Although stopping smoking can be hard, it is well worth the effort. Your health will benefit almost immediately. Just 20 minutes after your last cigarette, your heart rate slows. Twelve hours later, levels of carbon monoxide — a toxic gas — in your blood return to normal. Your lung function improves and your circulation starts to get better within three months. After a year, your risk of having a heart attack drops by half. And after five to 15 years, your stroke risk will be the same as that of a nonsmoker.

If you smoke, talk to your doctor about stopping smoking. Your doctor can provide medications and support and can also refer you to treatment programs in your area that can are available to help you. Stopping smoking is a process, so take it one step at a time.

— Richard D. Hurt, M.D., Nicotine Dependence Center, Mayo Clinic, Rochester, Minn.