About 12 hours after you smoke your last cigarette, the nicotine and carbon monoxide levels in your system drop substantially. After 10 to 15 years of not smoking, your risk of death from lung cancer or heart attack will be about the same as a person who never smoked. Your healthcare professional understands this. Recent research has shown that the nicotine in cigarettes works on the chemistry of your brain. Smokers know that by controlling the amount of nicotine they inhale, they can give themselves a lift or calm themselves down.
Nicotine works fast.
If you have smoked for at least a year, your body has become dependent upon nicotine and will fight you if you cut off the nicotine it needs to produce the chemical reward system you have become used to. Norepinephrine brings on withdrawal symptoms, and you may have A craving for tobacco, A desire for sweets, Increased coughing, and Impaired performance on vigilance tasks. In addition, you may become irritable, anxious, restless, or depressed. You may have trouble sleeping and concentrating. Your heart rate may decrease.