Smokers who quit may experience withdrawal symptoms including hunger, weight gain, restlessness, irritability, difficulty concentrating, sleep interruptions, fatigue, anxiety and depression. Physical symptoms may include headaches, nausea, decreased heart rate, decreased blood pressure and constipation. Some ex-smokers experience cravings for tobacco or for things that taste sweet.
Withdrawal symptoms come from the sudden removal of nicotine from the body. Nicotine is highly addictive, with 80 to 90 percent of smokers becoming addicted to the drug, according to Smokefree.gov. The brain and various parts of the body get used to the nicotine that comes with each cigarette.
When the smoker quits, the body no longer receives that nicotine, which can cause various uncomfortable physical, mental and emotional side effects. Nicotine withdrawal symptoms may feel so intense that the person begins smoking again. The rush of nicotine when the person smokes another cigarette may ease the withdrawal symptoms temporarily.
These side effects may last a few days or a few weeks. The intensity and length of time the symptoms last vary from one smoker to the next, though withdrawal symptoms are generally more pronounced for heavy smokers. The longer a former smoker goes without a cigarette, the less intense the symptoms typically become.