“What makes cigarettes so addictive is the nicotine in the tobacco,” said Dr. Adam Goldstein, director of Tobacco Intervention Programs at the University of North Carolina School of Medicine. “Nicotine is the hardest addiction to quit.” It enters the nervous system within seconds, attaching itself to receptors in the brain that release dopamine, which is commonly known as “the feel good hormone,” Goldstein explained. “You don’t even have to see someone else smoke, just thinking about it causes withdrawal symptoms.”

“Only about 5% of people succeed in quitting alone,” Goldstein said. Behavioral therapy doubles the quit rates compared with people who try to kick the habit with no support, he noted. “Pharmacotherapy, which is nicotine-replacement therapy using medication, also double the quit rates.” Social support works, too, but the best method is a combination of the two because the success rate is three or four times higher than when people try to stop smoking by themselves, Goldstein explained.

The only negative aspect of smoking cessation — which is certainly not a reason to keep smoking — is weight gain, especially among already overweight people. Nicotine decreases appetite and increases metabolism. “On average, a person gains about four pounds,” Goldstein said. “Obese people need a strategy to help manage their weight while they go through withdrawal.”

Some people find it hard to quit because smoking helps them calm down. This is true, but there is a twist and it has to do with the immediate reward and relief smoking provides. The body remembers that a person smoked when he or she felt stressed. So next time a stressful situation occurs, the body wants the same quick relief. “In reality, a smoker is not fighting stress, he is fighting withdrawal,” Goldstein said. “This is why withdrawal symptoms are what we have to focus on when we try to quit.”

E-cigarettes are not the way, Goldstein explained. “People don’t actually quit,” Most still smoke tobacco cigarettes, even though they may have cut down, he noted. “Electronic cigarettes are not FDA regulated, people still get some toxicity and very high levels of nicotine. We won’t know the real effects [of e-cigarettes] until 20 years from now; there are safer meds to quit,” he added.

To identify how exactly the body is affected when a person stops smoking, 24/7 Wall St. reviewed several studies on the effects of smoking and also consulted a medical doctor who conducts research on health policy and disparities in tobacco use and cessation.

Click here to see what happens to the body after you’ve smoked your last cigarette.